P0773 Electric Shift E Solenoid

⚙️ Critical Role of Solenoid “E”

Controls hydraulic pressure in the valve body
Manages gear shifts for specific ratios (e.g., 4→5 or 5→6 on 6-speed)
Fault → Disruption of shift sequences and transmission overheating

🚨 Immediate Symptoms

Gear slipping (engine RPM surges without acceleration)
Jolts when engaging (especially between 3rd and 4th gear)
Transmission overheating (burning smell + temperature warning light)
Limp mode activated (limited power, gears locked)
Check Engine + Overdrive warning lights (⚠️ flashing on Ford)

🔧 Common Causes (Order of Probability)

Rank	Cause	Details
1	Degraded transmission fluid	Low level, oxidation, metal contamination
2	Faulty Solenoid “E”	Burnt coil, stuck magnetized core
3	Damaged wiring	Chafed wires, corroded connectors (moisture)
4	Clogged valve body	Particles blocking jets
5	Internal failure	Burnt clutches, leaking seals
6	PCM failure	Rare (< 5%) – check companion codes

🔍 Diagnostic Procedure

Step 1: Preliminary Checks (30 min)

Fluid check:
- Level when hot (engine running)
- Color/smell: Bright red = OK, Brown/black + burnt smell = contamination
Visual inspection:
- Solenoid connectors (green corrosion = water infiltration)
- Wiring along the transmission (look for chafed areas)

Step 2: Electrical Tests

Test	Tool	Normal Values
Solenoid resistance	Multimeter Ω	20-30 Ω (depending on model)
Circuit continuity	Probe tester	0 Ω (PCM → solenoid)
PCM voltage	DC multimeter (ignition ON)	12V on power wire

Step 3: Advanced Analysis

OBD-II scanner specific to transmission (e.g., Ford IDS, Toyota TechStream):
- Monitor solenoid PIDs (% activation, current errors)
- Check line pressure (if sensor available)

🛠️ Repairs & Costs

Problem	Solution	Average Cost
Contaminated fluid	Drain + refill (flush if severe)	150-300 €
Faulty solenoid	Replacement (OEM part)	120-250 €
Damaged wiring	Harness repair	80-180 €
Valve body cleaning	Removal/ultrasonic cleaning	300-500 €
Transmission repair	Complete overhaul	1500-3000 €

⏱️ Service time: 2h (diagnosis) + 2h to 8h (repair).

⚠️ Risks of Ignoring the Code

Clutch destruction (repeated slipping → overheating)
Transmission lock-up in limp mode
Engine overheating (improper gear ratios → excessive RPM)

🔧 Pro Tips

First action:
- Check manufacturer TSB (e.g., Ford TSB #19-2367 on false P0773 for 2018 Focus)
Quick test:
- Disconnect solenoid connector → If code changes from P0773 to P0774, the solenoid is faulty.
Critical parts:
- Solenoid “E” Aisin TCC-SOL-006 (Toyota/Lexus)
- Solenoid BorgWarner E47339 (Chrysler/Dodge)
Common mistake:
- Forgetting to reset adaptations after repair (required on 80% of models)

📊 Workshop Statistics: 70% of P0773 resolved by solenoid replacement + complete fluid change.

Conclusion:
P0773 indicates a critical electrical or hydraulic fault. Recommended procedure:

Check fluid level/condition
Test solenoid resistance + wiring continuity
Replace solenoid if faulty → Reset PCM
Do not delay repair: Prolonged slipping costs 10x more in a full overhaul!

P0774 Intermittent Shift Solenoid E

What does it mean?

This is a generic diagnostic trouble code (DTC) and generally applies to OBD-II equipped vehicles with an automatic transmission.

This may include, but is not limited to, vehicles from Chrysler, Ford, Dodge, Hyundai, Kia, Ram, Lexus, Toyota, Mazda, Honda, VW, etc. Although generic, the exact repair steps may vary by year, make, model, and powertrain configuration.

Most automatic transmissions incorporate a number of shift solenoids, depending on the number of gears inside. The trouble codes related to this, the “E” shift solenoid, are codes P0770, P0771, P0772, P0773, and P0774 depending on the specific malfunction that alerts the PCM to set the code and turn on the Check Engine light. If you have an Overdrive light or other transmission warning light, it may also be illuminated.

The purpose of the shift solenoid circuit is for the PCM to monitor the shift solenoids to manage the movement of fluid between the different hydraulic circuits and change the gear ratio at the appropriate time. This process maximizes engine performance at the lowest possible RPM.

The automatic transmission relies on bands and clutches to shift gears, and this is accomplished by having fluid pressure in the right place at the right time. The transmission solenoids are responsible for opening or closing valves in the valve body to allow transmission fluid to flow to the clutches and bands to move the transmission smoothly as the engine accelerates.

When the Powertrain Control Module (PCM) detects a malfunction in the “E” shift solenoid circuit, a variety of codes can be triggered depending on the specific vehicle, transmission, and number of gears incorporated into the specific automatic transmission. In this case, the OBD-II trouble code P0774 is associated with an intermittent fault in the “E” shift solenoid circuit.

How severe is this DTC?

The severity of this code normally starts as moderate, but it can escalate to a more severe level quickly when not corrected in a timely manner.
What are some of the symptoms of the code?

Symptoms of a P0774 trouble code may include:

Transmission slipping
Transmission overheating
Transmission shifting harshly
Reduced fuel economy

Symptoms

potentially missed shifts
Vehicle enters limp mode
Check Engine light illuminated

What are some of the common causes of the code?

Causes

of this P0774 transmission code may include:

Insufficient fluid level
Dirty or contaminated fluid
Dirty or clogged transmission filter
Faulty transmission valve body
Restricted hydraulic passages
Transmission has an internal failure
Faulty shift solenoid
Corroded or damaged connector
Faulty or damaged wiring
Faulty PCM

What are the troubleshooting steps for P0774?

Before starting the troubleshooting process for any malfunction, you should research the Technical Service Bulletins (TSBs) for the specific vehicle by year, model, and transmission. In some circumstances, this can save you a lot of time in the long run by pointing you in the right direction. You should also check the vehicle’s records to verify the last time the filter and fluid were changed if possible.
Fluid and Wiring Inspections

The first step is to ensure the fluid level is correct and to inspect the condition of the fluid for any contamination. Next, a thorough visual inspection to check the associated wiring for obvious defects such as scraping, rubbing, bare wires, or burn spots should be performed.

Next, check the connectors and connections for security, corrosion, and damaged pins. This process should include all wiring and connectors for the transmission solenoids, transmission pump, and PCM. Based on the configuration, the transmission bonding should be inspected for security and bonding issues.
Advanced Steps

Advanced steps become very vehicle-specific and require appropriate advanced equipment to perform accurately. These procedures require a digital multimeter and the vehicle-specific technical references. Voltage requirements will be highly based on the specific year and model of the vehicle. You must follow the troubleshooting chart specific to your vehicle.
Continuity Checks

Continuity checks should always be performed with the power disconnected from the circuit, and normal readings for wiring and connections should be 0 ohms of resistance, unless otherwise indicated by the technical data. Resistance or lack of continuity is an indication of faulty wiring that is open or shorted and must be repaired or replaced.
What are the common repairs for this code?

Replacing fluid and filter
Repairing or replacing a faulty shift solenoid
Repairing or replacing the faulty transmission valve body
Repairing or replacing the faulty transmission
Flushing the transmission to clean passages
Cleaning corrosion from connectors
Repairing or replacing wiring
Reprogramming or replacing PCM

I hope the information in this article has been helpful in pointing you in the right direction to correct the issue with your shift solenoid circuit error code. This article is strictly informational, and the technical data and service bulletins specific to your vehicle should always take priority.

P0775 Pressure Control Solenoid B Malfunction

What Does It Mean?

This is a generic diagnostic trouble code (DTC) and generally applies to OBD-II equipped vehicles with an automatic transmission.

This can include, but is not limited to, vehicles from Ford, Mercury, Lincoln, Jaguar, Chevrolet, Toyota, Nissan, Allison/Duramax, Dodge, Jeep, Honda, Acura, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

When the OBD-II fault code P0775 is set, the Powertrain Control Module (PCM) has detected a problem with the transmission pressure control solenoid “B”. Most automatic transmissions have at least three solenoids, which are solenoids A, B, and C. Fault codes related to solenoid “B” are codes P0775, P0776, P0777, P0778, and P0779. The set of codes is based on the specific malfunction that alerts the PCM and illuminates the Check Engine light.

The purpose of transmission pressure control solenoids is to control fluid pressure for the proper operation of an automatic transmission. The PCM receives an electronic signal based on the pressure inside the solenoids. An automatic transmission is controlled by bands and clutches that shift gears by having fluid pressure in the right place at the right time. Based on signals from associated devices monitoring vehicle speed, the PCM commands the pressure solenoids to direct fluid at the appropriate pressure to various hydraulic circuits that change the transmission ratio at the right time.

The P0775 code is set by the PCM when the pressure control solenoid “B” experiences a general malfunction.

How Severe Is This DTC?

The severity of this code normally starts as moderate, but it can escalate to a more severe level quickly if not corrected in a timely manner.
What Are Some of the Symptoms of the Code?

Symptoms of a P0775 fault code may include:

Vehicle enters limp mode
Transmission slips when shifting gears
Transmission overheating
Transmission shifts harshly
Reduced fuel economy

Symptoms

Potential misfires
Check Engine light illuminated

What Are Some of the Common Causes of the Code?

Causes

of this P0775 transmission code may include:

Faulty pressure control solenoid
Dirty or contaminated fluid
Dirty or clogged transmission filter
Faulty transmission pump
Faulty transmission valve body
Restricted hydraulic passages
Corroded or damaged connector
Faulty or damaged wiring
Faulty PCM

What Are the Troubleshooting Steps for P0775?

The first step is to check the fluid level and examine the condition of the fluid for contamination. Before changing the fluid, you should check the vehicle’s records to verify the last time the filter and fluid were changed.

A detailed visual inspection to check the condition of the wiring for obvious defects is next. Check the connectors and connections for security, corrosion, and damaged pins. This should include all wiring and connectors for the transmission pressure control solenoids, transmission pump, and PCM. Depending on the configuration, the transmission pump may be electric or mechanical.
Advanced Steps

Advanced steps always become very vehicle-specific and require appropriate advanced equipment to perform accurately. These procedures require a digital multimeter and the vehicle-specific technical references. You must obtain the troubleshooting guidelines specific to your vehicle before proceeding with the advanced steps. Voltage requirements can be very specific to the particular vehicle model. Fluid pressure requirements will also vary depending on the transmission design and configuration.
Continuity Checks

Unless otherwise indicated in the technical data, normal readings for wiring and connections should be 0 ohms of resistance. Continuity checks should always be performed with the power disconnected from the circuit to avoid shorting the circuit and causing further damage. Resistance or lack of continuity is an indication of faulty wiring that is open or shorted and must be repaired or replaced.
What Are the Common Repairs for This Code?

Replacing fluid and filter
Replacing the faulty pressure control solenoid
Repairing or replacing a faulty transmission pump
Repairing or replacing the faulty transmission valve body
Flushing the transmission to clean passages
Cleaning connector corrosion
Repairing or replacing wiring
Programming or replacing PCM

Possible misdiagnosis may include:

Engine misfire issue
Transmission pump problem
Internal transmission problem
Transmission problem

I hope the information in this article has helped point you in the right direction to fix the issue with your pressure control solenoid fault code. This article is strictly informational, and the technical data and service bulletins specific to your vehicle should always take priority.

P0776 Pressure Control Solenoid B Performance or Stuck Off

What does it mean?

This is a generic diagnostic trouble code (DTC) and generally applies to OBD-II equipped vehicles with an automatic transmission.

This can include, but is not limited to, vehicles from Ford, Mercury, Lincoln, Jaguar, Chevrolet, Toyota, Nissan, Allison/Duramax, Dodge, Jeep, Honda, Acura, etc. Although generic, the exact repair steps may vary by year, make, model, and powertrain configuration.

When the OBD-II fault code P0776 is set, the Powertrain Control Module (PCM) has detected a problem with the transmission pressure control solenoid “B”. Most automatic transmissions have at least three solenoids, which are solenoids A, B, and C. Fault codes related to solenoid “B” are codes P0775, P0776, P0777, P0778, and P0779. The code set is based on the specific malfunction that alerts the PCM and illuminates the Check Engine light.

Transmission pressure control solenoids are designed to control fluid pressure for the proper operation of an automatic transmission. The PCM receives an electronic signal based on the pressure inside the solenoids. An automatic transmission is controlled by bands and clutches that shift gears by having fluid pressure in the right place at the right time. Based on signals from associated devices monitoring vehicle speed, the PCM commands the pressure solenoids to direct fluid at the appropriate pressure to various hydraulic circuits that change the transmission ratio at the right moment.

The P0776 code is set by the PCM when the pressure control solenoid “B” is not functioning correctly or is stuck in the “Off” position.

How severe is this DTC?

The severity of this code normally starts as moderate, but it can quickly escalate to a more severe level if not corrected in a timely manner.
What are some of the symptoms of the code?

Symptoms of a P0776 fault code may include:

The vehicle enters limp mode
Transmission slips when shifting gears
Transmission overheating
Transmission shifts harshly
Reduced fuel economy

Symptoms

Potential misfires, Check Engine light on

What are some common causes of the code?

Causes of this P0776 transmission code may include:

Faulty pressure control solenoid
Dirty or contaminated fluid
Dirty or clogged transmission filter
Faulty transmission pump
Faulty transmission valve body
Restricted hydraulic passages
Corroded or damaged connector
Faulty or damaged wiring
Faulty PCM

What are the troubleshooting steps for P0776?

Before starting the troubleshooting process for any malfunction, you should research Technical Service Bulletins (TSBs) for the specific vehicle by year, model, and transmission. In some circumstances, this can save you a lot of time in the long run by pointing you in the right direction. You should also check the vehicle’s records to verify the last time the filter and fluid were changed, if possible.
Fluid and Wiring Inspections

A detailed visual inspection to check the condition of the wiring for obvious defects is next. Check connectors and connections for security, corrosion, and damaged pins. This should include all wiring and connectors for the transmission pressure control solenoids, transmission pump, and PCM. Depending on the configuration, the transmission pump may be electric or mechanical.
Advanced Steps

Advanced steps always become very vehicle-specific and require appropriate advanced equipment to perform accurately. These procedures require a digital multimeter and vehicle-specific technical references. You should obtain troubleshooting guidelines specific to your vehicle before proceeding with advanced steps. Voltage requirements can be very specific to the particular vehicle model. Fluid pressure requirements will also vary depending on the transmission’s design and configuration.
Continuity Checks

Unless otherwise indicated in the technical data, normal readings for wiring and connections should be 0 ohms of resistance. Continuity checks should always be performed with the power disconnected from the circuit to avoid short-circuiting and causing further damage. Resistance or lack of continuity indicates faulty wiring that is open or shorted and must be repaired or replaced.
What are the common repairs for this code?

Replacing fluid and filter
Replacing the faulty pressure control solenoid
Repairing or replacing a faulty transmission pump
Repairing or replacing the faulty transmission valve body
Flushing the transmission to clean passages
Cleaning corrosion from connectors
Repairing or replacing wiring
Reprogramming or replacing the PCM

Possible misdiagnosis may include:

Engine misfire issue
Transmission pump problem
Internal transmission problem
Transmission issue

I hope the information in this article has helped guide you in the right direction to correct the issue with your pressure control solenoid fault code. This article is strictly informational, and the technical data and service bulletins specific to your vehicle should always take priority.

P0777 Pressure Control Solenoid B Stuck

What does it mean?

This is a generic diagnostic trouble code (DTC) and generally applies to OBD-II equipped vehicles with an automatic transmission.

This may include, but is not limited to, vehicles from Ford, Mercury, Lincoln, Jaguar, Chevrolet, Toyota, Nissan, Allison/Duramax, Dodge, Jeep, Honda, Acura, etc. Although generic, the exact repair steps may vary by year, make, model, and powertrain configuration.

When the OBD-II fault code P0777 is set, the Powertrain Control Module (PCM) has detected a problem with the transmission pressure control solenoid “B”. Most automatic transmissions have at least three solenoids which are the A, B, and C solenoids. Fault codes related to the “B” solenoid are codes P0775, P0776, P0777, P0778, and P0779. The code set is based on the specific malfunction that alerts the PCM and illuminates the Check Engine light.

The P0777 code is set by the PCM when the pressure control solenoid “B” is stuck in the “On” position.

Example of a transmission pressure control solenoid:
P0777 Transmission Pressure Control Solenoid
How severe is this DTC?

The severity of this code normally starts as moderate, but it can escalate to a more severe level quickly when not corrected in a timely manner.
What are some of the symptoms of the code?

Symptoms of a P0777 fault code may include:

Vehicle enters limp mode
Transmission slips when shifting gears
Transmission overheating
Transmission shifts harshly
Reduced fuel economy

Symptoms

Potential misfires
Check Engine light illuminated

What are some of the common causes of the code?

Causes

of this P0777 transmission code may include:

What are the troubleshooting steps for P0777?

Advanced steps always become very vehicle-specific and require appropriate advanced equipment to perform accurately. These procedures require a digital multimeter and the vehicle-specific technical references. You must obtain the troubleshooting guidelines specific to your vehicle before proceeding with the advanced steps. Voltage requirements can be very specific to the vehicle model. Fluid pressure requirements will also vary depending on the transmission design and configuration.
Continuity Checks

Replacing the fluid and filter
Replacing the faulty pressure control solenoid
Repairing or replacing a faulty transmission pump
Repairing or replacing the faulty transmission valve body
Flushing the transmission to clean the passages
Cleaning corrosion from connectors Repairing or replacing wiring
Reprogramming or replacing the PCM

A possible misdiagnosis may include:

Engine misfire problem
Transmission pump problem
Internal transmission problem
Transmission problem

P0778 Electric Pressure Control Solenoid B

What Does It Mean?

This is a generic diagnostic trouble code (DTC) and generally applies to OBD-II equipped vehicles with an automatic transmission.

When the OBD-II trouble code P0778 is set, the Powertrain Control Module (PCM) has detected a problem with the transmission pressure control solenoid “B”. Most automatic transmissions have at least three solenoids which are solenoids A, B, and C. The trouble codes related to solenoid “B” are codes P0775, P0776, P0777, P0778, and P0779. The set of codes is based on the specific malfunction that alerts the PCM and illuminates the Check Engine light.

The purpose of the transmission pressure control solenoids is to control fluid pressure for the proper operation of an automatic transmission. The PCM receives an electronic signal based on the pressure inside the solenoids. An automatic transmission is controlled by bands and clutches that shift gears by having fluid pressure in the right place at the right time. Based on signals from associated devices monitoring vehicle speed, the PCM commands the pressure solenoids to direct fluid at the appropriate pressure to various hydraulic circuits that change the gear ratio at the right moment.

The P0778 code is set by the PCM when the pressure control solenoid “B” experiences an electrical malfunction.
How severe is this DTC?

The severity of this code normally starts as moderate, but it can escalate to a more severe level quickly when not corrected in a timely manner.
What are some of the symptoms of the code?

Symptoms of a P0778 trouble code may include:

Vehicle enters limp mode
Transmission slips when shifting gears
Transmission overheating
Transmission shifts harshly
Reduced fuel economy

Symptoms

Potential misfires
Check Engine light illuminated

What are some of the common causes of the code?

Causes

of this P0778 transmission code may include:

What are the troubleshooting steps for P0778?

Before starting the troubleshooting process for any malfunction, you should research Technical Service Bulletins (TSBs) for the specific vehicle by year, model, and transmission. In some circumstances, this can save you a lot of time in the long run by pointing you in the right direction. You should also check the vehicle records to verify the last time the filter and fluid were changed if possible.
Fluid and Wiring Inspections

The first step is to check the fluid level and examine the condition of the fluid for contamination. Before changing the fluid, you should check the vehicle records to verify the last time the filter and fluid were changed.

Advanced steps always become very vehicle-specific and require appropriate advanced equipment to perform accurately. These procedures require a digital multimeter and the vehicle-specific technical references. You must obtain the troubleshooting guidelines specific to your vehicle before proceeding with the advanced steps. Voltage requirements can be very specific to the vehicle model. Fluid pressure requirements will also vary depending on the transmission design and configuration.
Continuity Checks

Unless otherwise specified in the technical data, normal readings for wiring and connections should be 0 ohms of resistance. Continuity checks should always be performed with the power disconnected from the circuit to avoid shorting the circuit and causing more damage. Resistance or lack of continuity is an indication of faulty wiring that is open or shorted and must be repaired or replaced.
What are the common repairs for this code?

Replacing the fluid and filter
Replacing the faulty pressure control solenoid
Repairing or replacing a faulty transmission pump
Repairing or replacing the faulty transmission valve body
Flushing the transmission to clean the passages
Cleaning corroded connectors
Repairing or replacing wiring
Reprogramming or replacing the PCM

Possible misdiagnosis may include:

Engine misfire issue
Transmission pump problem
Internal transmission problem
Transmission issue

I hope the information in this article has helped point you in the right direction to fix the issue with your pressure control solenoid trouble code. This article is strictly informational, and the technical data and service bulletins specific to your vehicle should always take priority.

P0779 Intermittent Pressure Control Solenoid B

What does it mean?

This is a generic diagnostic trouble code (DTC) and generally applies to OBD-II equipped vehicles with an automatic transmission.

When the OBD-II trouble code P0779 is set, the Powertrain Control Module (PCM) has detected a problem with the transmission pressure control solenoid “B”. Most automatic transmissions have at least three solenoids, which are solenoids A, B, and C. The trouble codes related to solenoid “B” are codes P0775, P0776, P0777, P0778, and P0779. The code set is based on the specific malfunction that alerts the PCM and illuminates the Check Engine light.

The P0779 code is set by the PCM when the pressure control solenoid “B” is operating intermittently.

How severe is this DTC?

The severity of this code normally starts as moderate, but it can escalate to a more severe level quickly when not corrected in a timely manner.
What are some of the symptoms of the code?

Symptoms of a P0779 trouble code may include:

Vehicle enters limp mode
Transmission slips when shifting gears
Transmission overheating
Transmission shifts harshly
Reduced fuel economy

Symptoms

Potential misfires
Check Engine light illuminated

What are some common causes of the code?

Causes

of this P0779 transmission code may include:

What are the troubleshooting steps for P0779?

Advanced steps always become very vehicle-specific and require appropriate advanced equipment to perform accurately. These procedures require a digital multimeter and the vehicle-specific technical references. You must obtain the troubleshooting guidelines specific to your vehicle before proceeding with the advanced steps. Voltage requirements can be very specific to the vehicle model. Fluid pressure requirements will also vary depending on the transmission design and configuration.
Continuity Checks

Replacing fluid and filter
Replacing the faulty pressure control solenoid
Repairing or replacing a faulty transmission pump
Repairing or replacing the faulty transmission valve body
Flushing the transmission to clean passages
Cleaning corrosion from connectors Repairing or replacing wiring
Reprogramming or replacing PCM

Possible misdiagnosis may include:

Engine misfire issue
Transmission pump problem
Internal transmission problem
Transmission issue

I hope the information in this article has helped point you in the right direction to correct the issue with your pressure control solenoid trouble code. This article is strictly informational, and the technical data and service bulletins specific to your vehicle should always take priority.

P077A Output Speed Sensor Circuit Loss of Direction Signal

What Does It Mean?

This generic powertrain diagnostic trouble code (DTC) generally applies to many OBD-II vehicles. This may include, but is not limited to, vehicles from Chevrolet, Ford, Toyota, Dodge, Honda, etc.

When your vehicle has stored a P077A code, it means the Powertrain Control Module (PCM) has detected a loss of directional signal from the output speed sensor.

Output speed sensors are typically of the electromagnetic variety. They use a certain type of toothed reluctor ring or gear that is permanently fixed to the transmission output shaft. When the output shaft rotates, it spins the reluctor ring. The raised teeth on the reluctor ring complete the output speed sensor circuit as they pass near the stationary electromagnetic sensor. As the reluctor passes by the sensor’s electromagnetic tip, the notches between the reluctor ring’s teeth create interruptions in the sensor circuit. This combination of circuit completions and interruptions is received by the PCM (and other controllers) as waveforms that represent the transmission output speed.

The sensor screws directly into the transmission case or is held in place with a bolt. An O-ring is used to prevent fluid leakage from the sensor opening.

The PCM compares the transmission input speed and output speed to determine if the transmission is shifting correctly and operating efficiently.

If a P077A code is stored, the PCM has detected an input voltage signal from the output speed sensor indicating that the reluctor ring is not moving. When the output speed sensor voltage signal does not fluctuate, the PCM assumes the reluctor ring has stopped unexpectedly. The PCM receives vehicle speed input data and wheel speed input data in addition to the output speed sensor data. By comparing these signals, the PCM can determine if the reluctor ring is moving sufficiently (based on the output speed sensor signal). A stationary output speed sensor signal can be caused by an electrical malfunction or a mechanical problem.

How Severe Is This DTC?

Conditions contributing to the storage of a P077A code can lead to (or result from) catastrophic transmission failure, so it should be addressed urgently.
What Are Some of the Symptoms of the Code?

Symptoms of a P077A engine code may include:

Intermittent operation of the speedometer/odometer
Abnormal transmission shifting patterns
Transmission slipping or delayed engagement
Activation/deactivation of the anti-skid system (if applicable)
Other transmission and/or ABS codes may be stored

What Are Some Common Causes of the Code?

Causes

of this code may include:

Faulty output speed sensor
Metal debris on the output speed sensor
Open or shorted circuits or connectors (especially near the output speed sensor)
Damaged or worn reluctor ring
Mechanical transmission failure

What Are the P077A Troubleshooting Steps?

I generally like to start my diagnosis of a P077A with a visual inspection of the system’s wiring and connectors. I would remove the output speed sensor and clean excessive metal debris from the magnetic tip. Be careful when removing the sensor as hot transmission fluid may leak from the sensor opening. Repair open or shorted circuits and connectors as needed.

Check the reluctor ring when the sensor is removed for inspection. If the reluctor ring is damaged, cracked, or has missing (or worn) teeth, you have likely found your problem.

Check the automatic transmission fluid if other transmission-related symptoms are present. The fluid should be relatively clean and not have a burnt smell. If the transmission fluid is more than a quarter low, top it off with the correct fluid and check for leaks. The transmission must be filled with the proper fluid and in good mechanical condition before proceeding with diagnosis.

I would need a diagnostic scanner with a built-in oscilloscope, a digital volt/ohmmeter (DVOM), and a reliable source of vehicle information to diagnose a P077A code.

I like to connect the scanner to the vehicle’s diagnostic port and then retrieve all stored trouble codes and freeze frame data. Before clearing the codes, I would write down this information as it might prove useful as my diagnosis progresses.

Look for applicable Technical Service Bulletins (TSBs) using your vehicle information source. Finding a TSB that matches the symptoms and stored codes (for the vehicle in question) will likely lead to a quick and accurate diagnosis.

Use the scanner’s data stream to observe the output speed during a vehicle road test. Limiting the data stream to display only relevant fields will increase the speed and accuracy of data delivery. Inconsistent or erratic signals from the input or output speed sensors can lead you to wiring, electrical connector, or sensor problems.

Disconnect the output speed sensor and use the DVOM to perform a resistance test. Your vehicle information source should provide wiring diagrams, connector views, connector pinout charts, and manufacturer-recommended testing procedures/specifications. If the output speed sensor does not meet specifications, it should be considered faulty.

Live data from the output speed sensor can be obtained using the oscilloscope. Probe the output speed sensor signal wire and the sensor ground wire. You may need to jack up or lift the vehicle to perform this type of test. Once the drive wheels are safely off the ground and the vehicle is secure, run the transmission while observing the waveform pattern on the oscilloscope. You are looking for flaws or inconsistencies in the waveform pattern created by the output speed sensor signal.

Disconnect the associated controllers’ connectors when performing circuit resistance and continuity tests with the DVOM. Failure to do so may damage the controller.

P0780 Malfunction of Gear Shift

What does it mean?

Based on my personal experience, when a P0780 code is stored, it means that the Powertrain Control Module (PCM) has detected a problem with automatic transmission shifting. This code can be due to a mechanical or electronic malfunction but is limited to vehicles with automatic transmissions.

Automatic transmissions in vehicles equipped with OBD-II are controlled by the PCM or a standalone Transmission Control Module (TCM). Input signals from a network of engine and transmission sensors are used by the transmission controller to calculate the transmission shift strategy. Electronic solenoids are then activated by the controller, allowing high-pressure fluid to flow into the appropriate hydraulic circuit (in the valve body) and enabling the transmission to upshift or downshift as needed.

A powerful pump (integrated into the transmission case and driven by the engine) is used to create the hydraulic pressure necessary to accomplish smooth and efficient shifting functions. Since different degrees of hydraulic pressure are required at different engine speeds and loads, the transmission controller regulates the pressure via an electronic pressure regulator. The transmission pressure sensor and transmission temperature sensor help the controller monitor hydraulic pressure and make necessary adjustments.

The transmission controller is programmed to compare input signals from the input speed sensor and output speed sensor to determine if the transmission is shifting effectively. If the PCM detects that the transmission is not shifting correctly, a P0780 code will be stored, and a Malfunction Indicator Lamp (MIL) may be illuminated. On some models, this type of code requires multiple drive cycles for the MIL to light up. In this case, the code may initially be displayed as a pending code.

Symptoms and Severity

A P0780 transmission shift malfunction code should be treated as urgent. A minor condition could turn into a catastrophic one if left unattended for an extended period.

Symptoms of a P0780 code may include:

Irregular transmission shifting patterns
Delayed transmission engagement
Harsh transmission shifts (especially if the controller has been placed in limp mode)
Transmission slipping
Transmission pump whining noise

Causes

Possible causes for setting this code are:

Short-circuited or open circuits in the transmission control harness
Low transmission fluid
Expired or burnt transmission fluid
Faulty shift solenoid(s)
Faulty input or output speed sensors
Bad electronic pressure regulator
Faulty transmission pump
Mechanical failure; including torque converter failure, clutch failure, or wear/breakage of internal components
A faulty PCM or PCM programming error

Diagnostic and Repair Procedures

You will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), a transmission pressure gauge, and a vehicle service manual (or All Data DIY) to diagnose a P0780 code.

A thorough visual inspection of the transmission and all associated wiring harnesses is the best place to start your diagnosis of this code. Pay close attention to wiring routed near hot exhaust components and sharp edges. Keep in mind that part of the transmission control harness is located inside the transmission case. You may choose to wait and see if you need to enter the transmission case (for other purposes) to inspect this part of the harness. Internal transmission harnesses are prone to failure due to the harsh temperatures and sharp edges found inside the automatic transmission.

Connect the scanner to the vehicle’s diagnostic connector and retrieve stored codes. Note the codes (along with any associated freeze frame data), then clear them from the PCM memory.

Since this code can be caused by an electronic or mechanical malfunction, you will also want to inspect the transmission, transmission cooler, and transmission cooling lines for signs of leakage. If the transmission is low on fluid, it will cause transmission slipping, improper shifting, and delayed engagement.

Either of these conditions can contribute to the storage of this code. If the transmission is slipping and there is delayed engagement (with normal fluid level), remove the dipstick (if applicable) and see if the fluid smells and looks burnt. If the fluid appears burnt, suspect a mechanical transmission failure that will require a rebuild, along with a new torque converter and cooler.

If the transmission fluid is significantly low (more than 2 quarts), you will need to locate and repair the leak, refill the transmission with the recommended fluid, and test the vehicle to see if the problem persists and the code is reset. If the code is reset, use the transmission pressure gauge to check the pump pressure. If the pump has run without enough fluid, it may have been damaged, resulting in a low-pressure condition that will also require a transmission overhaul.

If the symptoms are limited to a faulty shifting function, suspect a faulty wiring harness or shift solenoid. Follow the manufacturer’s recommendations for testing the transmission control wiring and shift solenoids.

Additional Diagnostic Notes:

Some models require the simultaneous replacement of all shift solenoids. If this applies to your vehicle, do not try to determine which shift solenoid is faulty; simply replace the solenoid harness.
Often, transmissions are rebuilt when an electrical malfunction is the cause of storing a P0780.

P0781 1-2 Gear Shift Malfunction

What does it mean?

In electronically controlled automatic transmission vehicles, the 1-2 shift solenoid is responsible for actuating the hydraulic circuits to engage the clutches or bands that change gears inside the automatic transmission. The shift solenoids are controlled either by a Transmission Control Module (TCM) or by the Engine Control Unit / Powertrain Control Module (ECU / PCM). The control circuit can be power-controlled or ground-controlled depending on the application.

Some vehicles automatically test the circuit even when the gear is not in use; the 1-2 shift solenoid can be an on/off solenoid or a duty cycle controlled solenoid. The PCM or TCM looks for an inductive kick to determine if the solenoid is functioning correctly even when it is not in use. This brief activation is too fast for the solenoid to actually cause a shift in the transmission. When the solenoid is activated and deactivated, the magnetic field collapses, sending a slightly higher voltage to the PCM, which is used to determine if the solenoid is operating correctly. Note: This DTC is almost identical to P0782, P0783, P0784, and P0829.

Symptoms

Symptoms of a DTC P0781 may include:

Check Engine Light is on (Malfunction Indicator Lamp / MIL)
The vehicle will not shift from 1st to 2nd gear

This condition may illuminate a Check Engine Light and possibly disable the transmission controls entirely, resulting in a fail-safe mode that will only allow a single default gear depending on the vehicle’s condition with all solenoids deactivated.

Causes

Potential causes of a P0781 code include:

    1-2 shift solenoid failure
    Electrical short to power – pinched wires
    Electrical short to ground – pinched wires
    Open circuit in power or ground wiring – disconnected or loose connections
    Internal TCM or PCM failure

Possible Solutions

Disconnect the PCM or TCM wiring harness, depending on the application, and using an electrical diagram as a reference, check for excessive resistance or an open in the control circuit. Using a Digital Volt-Ohm Meter (DVOM) set to the Ohms scale, check the resistance on the 1-2 solenoid’s power and ground sources to determine if there is an open circuit or excessive resistance in the 1-2 solenoid. Visually inspect for pinched, disconnected, or loose wires on the harness connectors.

Short to Power: Disconnect the positive battery cable and the wiring harness connector at the transmission and check for continuity using the DVOM between the power source and the solenoid circuit wiring in Key On Engine Off (KOEO) position as well as in Key Off position.

Short to Ground: Disconnect the positive battery cable and the wiring harness connector at the transmission and check for continuity using the DVOM between the 1-2 solenoid power source and a known good ground.

TCM or PCM Failure: Using an advanced scan tool capable of controlling solenoids, manually activate the 1-2 shift solenoid. It may be necessary to manually activate the transmission control relay on some vehicles if power is not present at the transmission wiring harness connector. If no scan tool is available, it will be necessary to monitor the 1-2 solenoid circuit to determine if the TCM or PCM is sending a power or ground signal to the 1-2 solenoid during vehicle operation.