Definition of Code P0976

The fault code P0976 indicates that the Powertrain Control Module (PCM) has detected a voltage in one of the shift solenoid control circuits that falls below the parameters set by the vehicle manufacturer.

What does code P0976 mean?

The shift solenoid control circuit is responsible for relaying voltage and input between the shifting system and the PCM. In the case of a P0976, a lack or insufficient voltage input has been reported in the PCM, which can lead to a range of issues for the vehicle’s transmission system.

What causes code P0976?

Problems with a broken electrical circuit between the solenoid control circuit and the PCM are the most likely cause of a P0976 fault code. Technicians report that the code is often the result of a vehicle stored in poor conditions for too long, or otherwise mishandled during a previous set of repairs.

There is very little chance that the PCM itself is faulty and reporting a false issue. Although this should only be considered once all other options have been exhausted, it is still something that can be taken into account if all other components related to the code check out correctly.

What are the symptoms of code P0976?

In the case of a P0976 fault code, the vehicle may experience gear slipping or failure to shift. One or more gears may be inaccessible due to a malfunction in the solenoid control circuit. Otherwise, the transmission system may behave erratically, depending on the severity of the solenoid control circuit malfunction. A fault code and an engine warning light on the dashboard will also be present to help diagnose the problem.

How does a mechanic diagnose code P0976?

A mechanic may first identify the P0976 code by reading it via an OBD-II scanner. The solenoid itself should be checked for any signs of disconnection or failure. Circuit checks must be performed between the shift solenoid control and the PCM itself using a voltmeter. This will help identify any potential circuit issues, if any. Ensure all connectors are properly connected and note any broken, corroded, or otherwise damaged wiring.

Common mistakes when diagnosing code P0976

Components related to the transmission or shift solenoid control circuit may be mistakenly replaced when the real problem lies in broken electrical wiring.

How severe is code P0976?

If one or more gears have been made inaccessible due to the P0976 fault code, it will severely affect the vehicle’s drivability. As with any fault code related to the vehicle’s transmission system, P0976 must be taken very seriously and addressed at the earliest opportunity.

What repairs can fix code P0976?

• Replace wiring identified as corroded, broken, or disconnected
• Replace or repair the faulty solenoid
• Replace or repair a faulty component

Definition of Code P0977

Fault code P0977 indicates a problem with the shift solenoid B control circuit.

What Does Code P0977 Mean?

Code P0977 is a standard OBD fault code that detects an issue with the shift solenoid B control circuit. Shift solenoids are used to help achieve smooth gear shifts in automatic transmissions. The various shift solenoids control the brakes, bands, and clutches within the transmission, with solenoid B varying by vehicle make and model. The Transmission Control Module (TCM) manages the shift solenoids, activating and deactivating them as needed to adjust gear ratios and facilitate smooth shifting. If the TCM records an abnormal voltage reading from the shift solenoid B control circuit, this circuit will be disabled, and the Powertrain Control Module (PCM) will log code P0977.

What Causes Code P0977?

Several factors can trigger code P0977:

• Faulty shift solenoid B
• Defective control circuit
• Damaged or faulty electrical components, such as wires, connectors, and fuses
• Low transmission fluid levels
• Dirty or contaminated transmission fluid
• In rare cases, a faulty PCM, TCM, or Engine Control Module (ECM)

What Are the Symptoms of Code P0977?

Fault code P0977 is typically accompanied by the “Check Engine Soon” light illuminating on the dashboard. The vehicle will often experience transmission issues, such as harsh shifting, delayed or abrupt acceleration, and an inability to access certain gears. It is also likely that the vehicle will have reduced fuel economy.

How Does a Mechanic Diagnose Code P0977?

Code P0977 will be addressed using a standard OBD-II fault code scanner. A qualified mechanic will use the scanner to review freeze frame data and assess the code. Any additional fault codes should also be checked and, if found, addressed in the order displayed by the scanner. The fault codes will then need to be reset, and the vehicle restarted so the technician can see if the code remains detected. If not, a false trigger or intermittent error is the most likely culprit.

If code P0977 returns, the mechanic will check the transmission fluid. If the fluid is low, it should be refilled, and the mechanic must carefully look for signs of leaks. If the fluid is dirty, it can be flushed and replaced, but if it is contaminated, the transmission is likely severely damaged. This will probably require a full replacement or rebuild. Next, the mechanic should visually inspect the electrical components and replace any wires, connectors, or fuses that are damaged or compromised.

If the issue is still not found, a digital volt/ohmmeter can be used to help identify the circuit corresponding to shift solenoid B. Once the correct circuit is verified, the solenoid, wiring harness, and circuit should all be inspected.

Whenever the technician replaces or repairs a component, the fault codes must be reset and the vehicle restarted to check if the code reappears. This helps the technician determine when the problem is resolved.

Common Mistakes When Diagnosing Code P0977

The most frequent mistake when diagnosing this code is failing to follow the OBD-II diagnostic protocol. It is crucial for technicians to always adhere to the step-by-step protocol to ensure thorough and efficient diagnosis and repair.

Shift solenoids are often unnecessarily replaced when the only issue is something simpler, such as a shorted wire or dirty transmission fluid.

How Severe Is Code P0977?

A vehicle with fault code P0977 will still be operable, though it may experience transmission problems severe enough to make driving impractical. If code P0977 is not addressed, it can cause further damage to the transmission, so it is important to have the vehicle inspected as soon as the code is noticed.

What Repairs Can Fix Code P0977?

Repairs for fault code P0977 include:

• Replacing shift solenoid B
• Replacing electrical components
• Replacing or adding transmission fluid
• In very rare cases, replacing the PCM, ECM, or TCM

Each shift solenoid is responsible for controlling different clutches and gears. If a particular shift solenoid does not operate as it has been programmed to, a DTC P0978 will be recorded.

How severe is the code?

Although the severity of a diagnostic code P0978 may not seem too bad at first, transmission problems will worsen, eventually leading to a transmission that will not shift gears.

Symptoms

Symptoms of a P0978 include:

• Harsh shifts
• The transmission cannot shift into gear

Causes

• Low transmission fluid
• Dirty fluid/filter
• Damaged wiring and/or corroded or broken connectors
• Malfunctioning shift solenoid

How to diagnose the code?

Transmission fluid is very important for the operation of a shift solenoid. Believe it or not, dirty or low transmission fluid can actually trigger an OBDII fault code P0978, which should be the first thing to check. Damaged wiring or broken connectors along the transmission wiring harness can also cause this OBD2 code. If no issues are detected in either of these areas, the C shift solenoid should be checked.

What repairs will fix P0978?

• Service the transmission
• Replace or repair damaged wiring/connectors
• Replace the shift solenoid

The ECU controls the shift solenoids by sending an electric current through a coil of wire that is wrapped around the piston mechanism inside the solenoid. If the computer detects an unusually low voltage situation somewhere along the shift solenoid C control circuit, it will store a DTC P0979.

How severe is the code?

Diagnostic code P0979 is triggered when the ECU has trouble controlling shift solenoid C (also known as number three). Transmission problems related to this OBDII code may not be very serious at first. But they will continue to worsen and eventually render a transmission non-functional.

Symptoms

Symptoms of a P0979 include:

• Exceptionally hard shifts
• The transmission cannot shift into gear

Causes

• Low transmission fluid level
• Dirty fluid/filter
• Corroded/broken connectors and/or damaged wiring
• Malfunctioning shift solenoid

How to diagnose the code?

Diagnosing an OBDII P0979 code should begin with a check of the transmission fluid. If it is dirty or low, this OBD2 code will be triggered. Damaged wiring or broken/corroded connectors can also cause problems with a solenoid. If none of these issues are present, the shift solenoid C itself will need to be tested.

What repairs will fix P0979?

• Service the transmission
• Replace or repair damaged wiring/connectors
• Replace the shift solenoid

Whenever the computer instructs the transmission to shift gears, it activates a shift solenoid by sending an electrical charge through a coil of wire wrapped around the solenoid mechanism. If there is an abnormally high signal from the shift solenoid C control circuit, a DTC P0980 will be triggered.

How severe is the code?

The severity of a diagnostic code P0980 may not be too bad initially. However, the transmission issues associated with this OBDII code will eventually intensify to the point that the transmission will not function properly.

Symptoms

Symptoms of a P0980 include:

• Harsh shifting
• Transmission cannot shift into gear

Causes

• Transmission fluid level is too low
• Transmission fluid is too dirty
• Damaged/broken wires
• Broken/corroded connectors
• Shift solenoid failure

How to diagnose the code?

Dirty or low transmission fluid will actually cause an OBDII P0980 trouble code, so this must be checked first. If the ATF is clean and bright, then the wiring and connectors along the transmission wiring harness need to be inspected. If no broken wires or corroded/broken connectors are found, the shift solenoid C will need to be checked.

What repairs will fix P0980?

• Service the transmission
• Replace or repair damaged wires/connectors
• Replace the shift solenoid

Whenever the transmission shifts gears, pressurized hydraulic fluid is used to achieve this. This pressure is directed by small piston-like devices called solenoids. If the ECU detects that the shift solenoid D is not operating according to its preprogrammed parameters, a DTC P0981 will be recorded.

How severe is the code?

Although the symptoms associated with a diagnostic code P0981 may not be very severe initially, they can quickly worsen to the point where your vehicle cannot be driven safely.

Symptoms

Symptoms of a P0981 include:

• Harsh shifting
• Transmission cannot shift into gear

Causes

• Low transmission fluid level
• Dirty fluid/filter
• Corroded/broken connectors and/or damaged wiring
• Malfunctioning shift solenoid

How to diagnose the code?

Since shift solenoids are designed to control the flow of pressurized transmission fluid, the level and condition of the transmission fluid can have a huge effect on their operation. Therefore, diagnosing an OBDII P0981 trouble code should start with checking the transmission fluid level and condition. Provided it is clean and at the correct level, the wiring and connectors along the transmission wiring harness will need to be inspected for signs of damage and corrosion. If no issues are found at this point, the shift solenoid D itself will need to be inspected.

What repairs will fix P0981?

• Service the transmission
• Replace or repair damaged wiring/connectors
• Replace the shift solenoid

Related Codes

P0982 – Shift Solenoid “D” Control Circuit Low
P0983 – Shift Solenoid “D” Control Circuit High

Shift solenoids function as small traffic control devices, which are used by the ECU to direct the flow of pressurized transmission fluid through the gearbox. This allows clutches and gears to be moved inside the transmission and shift gears. If the ECU detects low voltage in the shift solenoid D control circuit, it will store a DTC P0982.

How severe is the code?

Although transmission issues related to a diagnostic trouble code P0982 may not seem very significant at first. They will eventually become very serious and hinder the safe operation of your vehicle.

Symptoms

Symptoms of a P0982 include:

• Exceptionally hard
• The transmission cannot shift into gear

Causes

• Low transmission fluid
• Dirty fluid/filter
• Damaged wiring and/or corroded or broken connectors
• Malfunctioning shift solenoid

How to diagnose the code?

The level and condition of the transmission fluid are the first things that need to be checked when attempting to diagnose an OBDII P0982 fault code. The next thing to check is the condition of the wiring and connectors along the transmission wiring harness. If no broken wires or damaged connectors are found, the D shift solenoid itself must be tested.

What repairs will fix P0982?

• Service the transmission
• Replace or repair damaged wiring/connectors
• Replace the shift solenoid

Shift solenoids are typically located inside the valve body and are used by the computer to control the flow of pressurized hydraulic fluid (also called transmission fluid). If there is an abnormally high signal through the shift solenoid D control circuit, a DTC P0983 will be stored.

How severe is the code?

Diagnostic code P0983 is extremely severe, and the associated transmission problems will eventually leave you with a non-functional vehicle.

Symptoms

Symptoms of a P0983 include:

• Firm shifts
• Transmission cannot shift into gear

Causes

• Dirty fluid/filter
• Low transmission fluid
• Damaged wiring
• Corroded/broken connectors
• Shift solenoid is broken

How to diagnose the code?

The condition and level of the transmission fluid are very important for the operation of the shift solenoid. Therefore, this should be the first thing to check when trying to diagnose an OBDII trouble code P0983. The next thing to consider is the condition of the wiring and connectors along the transmission wiring harness. If no broken wires or corroded connectors are found, then the shift solenoid D itself will need to be inspected.

What repairs will fix P0983?

• Service the transmission
• Replace or repair damaged wiring/connectors
• Replace the shift solenoid

Related Codes

P0981 – Shift solenoid “D” control circuit range/performance
P0982 – Shift solenoid “D” control circuit low

Solenoids are typically numbered by letters, so the shift solenoid E is actually the 5th solenoid in the transmission, and it may be responsible for a number of gears/actions. If your vehicle has a DTC P0984, it means that the shift solenoid E is not operating according to preprogrammed parameters.

How severe is the code?

A diagnostic code P0984 essentially means that one or more of the gears inside your transmission are about to stop functioning. So yes, it is very serious.

Symptoms

Symptoms of a P0984 include:

• Transmission seems to engage
• Transmission cannot shift into gear

Causes

• Dirty transmission fluid
• Low transmission fluid
• Damaged connectors and/or wiring
• Faulty shift solenoid

How to diagnose the code?

A shift solenoid is used to control the flow of pressurized transmission fluid, so the condition and level of the transmission fluid are extremely important for the operation of said solenoids. Therefore, when trying to diagnose an OBDII fault code P0984, the transmission fluid should be the first thing that is checked. The next thing that needs to be checked is the condition of the wiring and/or connectors along the transmission wiring harness. After that, the shift solenoid E itself will need to be checked.

What repairs will fix P0984?

• Service the transmission
• Replace or repair damaged wiring/connectors
• Replace the shift solenoid

Each shift solenoid is responsible for certain actions within the transmission, such as engaging clutches or gears. It accomplishes these actions by directing the flow of pressurized transmission fluid into the correct channel. If the ECU detects an abnormally low voltage signal from the shift solenoid E control circuit, it will log a DTC P0985.

How severe is the code?

If the ECU detects a low voltage signal from shift solenoid E (i.e., solenoid number five), it means the solenoid is not responding correctly, which will result in a number of transmission problems. Therefore, a P0985 diagnostic code is very severe.

Symptoms

Symptoms of a P0985 include:

• Shifts are harsh and rough
• The transmission cannot shift into gear

Causes

• Transmission fluid is too low or too dirty
• Damaged wiring and/or connectors
• Faulty shift solenoid

How to diagnose the code?

The diagnostic process for a P0985 OBDII trouble code should begin with an inspection of the transmission fluid level and condition. Dirty transmission fluid can actually hinder solenoid operation, so the transmission must be serviced immediately if the level and condition do not meet specifications. The wiring and connectors along the transmission wiring harness will also need to be carefully inspected. If no broken wires or damaged/corroded connectors are found, then shift solenoid E must be checked.

What repairs will fix P0985?

• Service the transmission
• Replace or repair damaged wiring/connectors
• Replace the shift solenoid

Related Codes

P0984 – Shift Solenoid “E” Control Circuit Range/Performance
P0986 – Shift Solenoid “E” Control Circuit High