What Does Code P064C Mean?

The diagnostic code P064C is a generic OBD-II code applicable to many vehicles produced from 1996 onwards. It can involve various manufacturers such as Chrysler, Ford, General Motors, Mercedes-Benz, Nissan, Toyota, and many others. Although generic, the repair steps may vary depending on the year, make, model, and engine configuration.

A P064C code indicates that the Powertrain Control Module (PCM) has detected a problem with the glow plug control module. The latter controls the timing and activation of the glow plugs, which are essential in diesel engines to facilitate starting.

The glow plug control module can be independent or integrated into the PCM. When powered on, the PCM performs self-tests to check the operation of various modules using the communication network (CAN). If a problem is detected, the P064C code is stored and the Malfunction Indicator Lamp (MIL) may illuminate.

Severity of Code P064C

Code P064C is considered serious. A malfunction of the glow plugs can prevent the engine from starting, especially in cold weather.

Symptoms of Code P064C

Here are the most common symptoms associated with this code:

• Faulty glow plugs;
• Difficulty or delay in starting, especially in cold weather;
• Engine stalling during startup;
• Engine performance issues;
• Appearance of other diagnostic codes.

Possible Causes

Potential causes of code P064C include:

• Faulty glow plug controller or PCM;
• Damaged power supply circuit of the control module;
• PCM programming error;
• Open or short circuit in the glow plug circuit.

Diagnostic and Troubleshooting Steps

To diagnose code P064C, you will need a diagnostic scanner, a digital voltmeter/ohmmeter (DVOM), and reliable technical documentation for the vehicle.

1. Check for Technical Service Bulletins (TSBs)
   Consult relevant TSBs for vehicle-specific information related to the code.

2. Scan the Vehicle
   Retrieve stored codes and freeze frame data. Clear the codes, then test the vehicle to see if the problem persists. If the code does not return immediately, it may be intermittent.

3. Check Power Circuits
   Using the electrical diagram, check the battery voltage on the glow plug control circuit. If there is no voltage, inspect fuses, relays, and replace faulty components if necessary.

4. Inspect Wiring and Connections
   Examine cable harnesses and ground connections. Ensure there are no breaks, short circuits, or corrosion.

5. Inspect the Control Module
   Look for signs of damage (water, heat, impact). Any module showing such signs will need to be replaced.

6. Check Ground Circuits
   Test the integrity of ground connections using the DVOM.

7. Reprogram or Replace the Faulty Module
   If the circuits are in good condition, suspect a faulty control module or a programming error. Any replacement will require proper reprogramming.

By following these methodical steps, you can effectively diagnose and repair a P064C code.

What does it mean?

This is a generic diagnostic trouble code (DTC) for the powertrain and generally applies to OBD-II vehicles. This may include, but is not limited to, vehicles from Ford, Mazda, Smart, Land Rover, Dodge, Ram, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

When a P064D code is stored, it means that the Powertrain Control Module (PCM) has detected an internal processor performance error with the Heated Oxygen Sensor (HO2S) circuit for engine bank one. Other controllers may also detect an internal PCM performance error (with the HO2S circuit for bank one) and result in the storage of a P064D.

Bank 1 refers to the engine bank that contains cylinder number one.

The HO2S is composed of a zirconium dioxide sensing element and a tiny sampling chamber enclosed in a vented steel housing. The sensing element is connected to the conductor wires of the HO2S wiring harness with small platinum electrodes. The HO2S wiring harness is connected to the engine control harness, which provides the PCM with data regarding the percentage of oxygen in the engine’s exhaust gases compared to the oxygen content of the ambient air.

The upstream HO2S is located in the exhaust pipe (between the exhaust manifold and the catalytic converter). The most common method for this is to insert the sensor directly into a threaded boss that is welded into the exhaust pipe. The threaded boss is placed in the downpipe at the most convenient position and angle for sensor access and optimal functionality. Removal and installation of threaded oxygen sensors will require specially designed wrenches or sockets, depending on the vehicle application. The HO2S may also be secured using threaded studs (and nuts) welded to the exhaust pipe.

Exhaust gases are pushed through the exhaust manifold and into the downpipe where they pass over the upstream HO2S. The exhaust gases flow through specially designed vent holes in the HO2S steel housing and through the sensing element. Ambient air is drawn into a small sampling chamber at the center of the sensor, through openings in the conductor wires. In this chamber, the air is heated, forcing ions to produce a voltage (energy). Variations between the concentration of oxygen molecules in the exhaust gases and the ambient air (drawn into the HO2S) create fluctuations in the oxygen ion concentration (inside the sensor). These fluctuations cause the oxygen ions (inside the HO2S) to bounce (rapidly and repeatedly) from one platinum layer to the other. As the oxygen ions move between the platinum layers, it causes voltage changes. These voltage changes are recognized by the PCM as variations in exhaust oxygen concentration and reflect whether the engine is running lean (too little fuel) or rich (too much fuel). When more oxygen is present in the exhaust (lean condition), the voltage signal emitted by the HO2S is lower. When less oxygen is present in the exhaust (rich condition), the voltage signal output is higher. This data is used by the PCM to calculate, among other things, the fuel delivery strategy and ignition timing.

The upstream HO2S typically oscillates between 100 and 900 millivolts (0.1 and 0.9 volts), when the engine is idling and the PCM is operating in closed loop. In closed loop operation, the PCM considers the input signals from the upstream HO2S sensors to regulate the fuel injector pulse width and (ultimately) the fuel delivery. When the engine switches to open loop mode (under cold start and wide-open throttle conditions), the fuel delivery strategy is pre-programmed.

The internal control module monitoring processors are responsible for various controller self-test tasks and the overall responsibility of the internal control module. The HO2S input and output signals are subjected to self-test and are continuously monitored by the PCM and other associated controllers. The Transmission Control Module (TCM), the Traction Control System Module (TCSM), and other controllers also interact with the HO2S.

Whenever the ignition is turned on and the PCM is powered up, the HO2S self-tests are initiated. In addition to running internal controller self-tests, the Controller Area Network (CAN) also compares the signals from each individual module to ensure that each controller is functioning correctly. These tests are performed simultaneously.

If the PCM detects an internal anomaly in the HO2S functionality, a P064D code will be stored and a Malfunction Indicator Lamp (MIL) may be illuminated. Additionally, if the PCM detects a problem between any of the onboard controllers, which would indicate an internal HO2S error, a P064D code will be stored and a Malfunction Indicator Lamp (MIL) may be illuminated. Multiple failure cycles may be required for the MIL to illuminate, depending on the perceived severity of the malfunction.

Photo of a PCM with the cover removed:

Powertrain Control Module PCM
How severe is this DTC?

Internal Control Module Processor codes should be classified as severe.

A stored P064D code could lead to a variety of driving issues, including decreased fuel efficiency.
What are some of the symptoms of the code?

Symptoms of a P064D fault code may include:

Reduced fuel efficiency
A general lack of engine performance
A variety of engine driving symptoms
Other stored diagnostic trouble codes

What are some of the common causes of the code?

Causes

of this P064D DTC code may include:

Faulty controller or controller programming error
Faulty HO2S
Rich or lean exhaust conditions
Burned, chafed, broken, or disconnected wiring and/or connectors
Engine exhaust leaks
A faulty controller power relay or blown fuse
Open or shorted circuit or connectors in the CAN harness
Insufficient control module ground

What are the P064D troubleshooting steps?

Even for the most experienced and well-equipped professional technician, diagnosing a P064D code can be very challenging. There is also the issue of reprogramming. Without the necessary reprogramming equipment, it will be impossible to replace a faulty controller and perform a successful repair.

If ECM/PCM power codes are present, they will obviously need to be corrected before attempting to diagnose a P064D.

There are several preliminary tests that can be performed before declaring a controller faulty. A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable source of vehicle information will be necessary.

Connect the scanner to the vehicle’s diagnostic port and retrieve all stored codes and freeze frame data. You will want to note this information, just in case the code proves to be intermittent. After recording all relevant information, clear the codes and test-drive the vehicle until the code resets or the PCM enters readiness mode. If the PCM enters readiness mode, the code is intermittent and will be more difficult to diagnose. The condition that caused the P064D to be stored may even need to worsen before a diagnosis can be made. If the code resets, continue with this short list of preliminary tests.

When trying to diagnose a P064D, information can be your best tool. Search your vehicle information source for Technical Service Bulletins (TSBs) that parallel the stored code, the vehicle (year, make, model, and engine), and the symptoms presented. If you find the right TSB, it can provide diagnostic information that will assist you significantly.

Use your vehicle information source to obtain connector face views, connector pinout diagrams, component locators, wiring schematics, and diagnostic flowcharts related to the code and the specific vehicle.

Use the DVOM to test the controller power fuses and relays. Test and replace blown fuses as needed. Fuses should be tested with the circuit loaded.

If all fuses and relays appear to be functioning as expected, a visual inspection of the wiring and harnesses related to the controller is necessary. You will also want to check the chassis and engine ground junctions. Use your vehicle information source to obtain ground locations for the related circuits. Use the DVOM to test ground integrity.

Visually inspect the system controllers for signs of water, heat, or collision damage. Any damaged controller, especially by water, should be considered faulty.

If the controller power and ground circuits are intact, suspect a faulty controller or a controller programming error. Replacing the controller will require reprogramming. In some cases, you can purchase pre-programmed controllers through aftermarket sources. Other vehicles/controllers will require onboard reprogramming that can only be performed by a dealership or another qualified source.
HO2S Test

Ensure the engine is running efficiently before attempting to diagnose the HO2S. Misfire codes, throttle position sensor codes, manifold air pressure code, and mass air flow sensor codes should be addressed before attempting to diagnose HO2S or lean/rich exhaust codes.

Some automobile manufacturers use a fused circuit to supply voltage to the HO2S system. Test these fuses using the DVOM.

If all fuses are in good working order, locate the HO2S for engine bank one. The vehicle will need to be raised on an appropriate hoist or lifted and secured on safety stands. Once you have accessed the sensor in question, disconnect the harness connector and turn the ignition key to the ON position. You are looking for battery voltage at the HO2S connector. Use the wiring schematic to determine the circuit used to supply battery voltage. Also check the system ground at this point.

If HO2S voltage and ground are present, reconnect the HO2S. Start the engine and test-drive the vehicle. After a test drive, let the engine idle (with the transmission in neutral or park). Use the scanner to observe the HO2S input data. Limit the data stream scope to include only relevant data, and you will get a faster data response. Assuming the engine is running efficiently, the upstream HO2S should switch from rich to lean (and vice versa) regularly with the PCM in closed loop.

Unlike most other codes, P064D is likely caused by a faulty controller or a controller programming error
Test the system ground integrity by connecting the DVOM’s negative test lead to ground and the positive test lead to battery voltage

What does it mean?

This is a generic diagnostic trouble code (DTC) for the powertrain and generally applies to OBD-II vehicles. This may include, but is not limited to, vehicles from Ford, Mazda, Smart, Land Rover, Dodge, Ram, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

When a P064E code is stored, it means that the Powertrain Control Module (PCM) has detected an internal processor performance error related to the Heated Oxygen Sensor (HO2S) circuit for engine bank two. Other controllers may also detect an internal PCM performance error (related to the HO2S circuit for bank one) and result in the storage of a P064E code.

Bank 2 refers to the engine bank that does not contain cylinder number 1.

The HO2S consists of a zirconium dioxide sensing element and a tiny sampling chamber enclosed in a vented steel housing. The sensing element is connected to the conductor wires of the HO2S wiring harness with small platinum electrodes. The HO2S wiring harness is connected to the engine control harness, which provides the PCM with data regarding the percentage of oxygen in the engine’s exhaust gases compared to the oxygen content in the ambient air.

The upstream HO2S is located in the exhaust pipe (between the exhaust manifold and the catalytic converter). The most common method for this is to insert the sensor directly into a threaded boss that is welded into the exhaust pipe. The threaded boss is placed in the downpipe at the most convenient position and angle for sensor access and optimal functionality. Removal and installation of threaded oxygen sensors will require specially designed wrenches or sockets, depending on the vehicle application. The HO2S may also be secured using threaded studs (and nuts) welded to the exhaust pipe.

Exhaust gases are pushed through the exhaust manifold and into the downpipe where they pass over the upstream HO2S. The exhaust gases flow through specially designed vent holes in the HO2S steel housing and through the sensing element. Ambient air is drawn into a small sampling chamber in the center of the sensor, through openings in the conductor wires. In this chamber, the air is heated, forcing ions to produce a voltage (energy). Variations between the concentration of oxygen molecules in the exhaust gases and the ambient air (drawn into the HO2S) create fluctuations in the oxygen ion concentration (inside the sensor). These fluctuations cause the oxygen ions (inside the HO2S) to bounce (rapidly and repeatedly) from one platinum layer to the other. As the oxygen ions move between the platinum layers, it causes voltage changes. These voltage changes are recognized by the PCM as variations in exhaust oxygen concentration and reflect whether the engine is running lean (too little fuel) or rich (too much fuel). When more oxygen is present in the exhaust (lean condition), the voltage signal output by the HO2S is lower. When less oxygen is present in the exhaust (rich condition), the voltage signal output is higher. This data is used by the PCM to calculate, among other things, fuel delivery strategy and ignition timing.

The upstream HO2S typically oscillates between 100 and 900 millivolts (0.1 and 0.9 volts) when the engine is idling and the PCM is operating in closed loop. In closed-loop operation, the PCM considers input signals from the upstream HO2S sensors to regulate the fuel injector pulse width and (ultimately) fuel delivery. When the engine enters open-loop mode (during cold start and wide-open throttle conditions), the fuel delivery strategy is pre-programmed.

The internal control module monitoring processors are responsible for various controller self-test tasks and the overall responsibility of the internal control module. HO2S input and output signals are subjected to self-test and are continuously monitored by the PCM and other associated controllers. The Transmission Control Module (TCM), Traction Control System Module (TCSM), and other controllers also interact with the HO2S.

Whenever the ignition is turned on and the PCM is powered up, HO2S self-tests are initiated. In addition to running internal controller self-tests, the Controller Area Network (CAN) also compares the signals from each individual module to ensure each controller is functioning correctly. These tests are performed simultaneously.

If the PCM detects an internal anomaly in HO2S functionality, a P064E code will be stored, and a Malfunction Indicator Lamp (MIL) may be illuminated. Furthermore, if the PCM detects a problem between any of the onboard controllers that would indicate an internal HO2S error, a P064E code will be stored, and a Malfunction Indicator Lamp (MIL) may be illuminated. Multiple failure cycles may be required for MIL illumination, depending on the perceived severity of the malfunction.

Photo of a PCM with the cover removed

:
Powertrain Control Module PCM
How severe is this DTC?

Internal Control Module Processor codes should be classified as severe.

A stored P064E code could lead to various driving issues, including decreased fuel efficiency.
What are some of the symptoms of the code?

Symptoms of a P064E fault code may include:

Reduced fuel efficiency
A general lack of engine performance
A variety of engine driving symptoms
Other stored diagnostic trouble codes

What are some common causes of the code?

Causes

of this P064E DTC code may include:

Faulty controller or controller programming error
Faulty HO2S
Rich or lean exhaust conditions
Burned, chafed, broken, or disconnected wiring and/or connectors
Engine exhaust leaks
A faulty controller power relay or blown fuse
Open or shorted circuit or connectors in the CAN harness
Insufficient control module ground

What are the P064E troubleshooting steps?

Even for the most experienced and well-equipped professional technician, diagnosing a P064E code can be very challenging. There is also the issue of reprogramming. Without the necessary reprogramming equipment, it will be impossible to replace a faulty controller and perform a successful repair.

If ECM/PCM power codes are present, they will obviously need to be rectified before attempting to diagnose a P064E.

There are several preliminary tests that can be performed before declaring a controller faulty. A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable source of vehicle information will be necessary.

Connect the scanner to the vehicle’s diagnostic port and retrieve all stored codes and freeze frame data. You will want to note this information, just in case the code proves to be intermittent. After recording all relevant information, clear the codes and test-drive the vehicle until the code resets or the PCM enters readiness mode. If the PCM enters readiness mode, the code is intermittent and will be more difficult to diagnose. The condition that caused the P064E to be stored may even need to worsen before a diagnosis can be made. If the code resets, continue with this short list of preliminary tests.

When trying to diagnose a P064E, information can be your best tool. Search your vehicle information source for Technical Service Bulletins (TSBs) that parallel the stored code, the vehicle (year, make, model, and engine), and the symptoms presented. If you find the right TSB, it can provide diagnostic information that will assist you significantly.

Use your vehicle information source to obtain connector face views, connector pinout diagrams, component locators, wiring schematics, and diagnostic flowcharts related to the code and the specific vehicle.

Use the DVOM to test the controller power fuses and relays. Test and replace blown fuses as needed. Fuses should be tested with the circuit loaded.

If all fuses and relays appear to be functioning as expected, a visual inspection of the wiring and harnesses related to the controller is warranted. You will also want to check the chassis and engine ground junctions. Use your vehicle information source to obtain ground locations for the related circuits. Use the DVOM to test ground integrity.

Visually inspect the system controllers for signs of water, heat, or collision damage. Any damaged controller, especially by water, should be considered faulty.

If the controller power and ground circuits are intact, suspect a faulty controller or a controller programming error. Replacing the controller will require reprogramming. In some cases, you can purchase pre-programmed controllers through aftermarket sources. Other vehicles/controllers will require onboard reprogramming that can only be performed by a dealership or another qualified source.
HO2S Test

Ensure the engine is running efficiently before attempting to diagnose the HO2S. Misfire codes, throttle position sensor codes, manifold air pressure codes, and mass air flow sensor codes should be addressed before attempting to diagnose HO2S or lean/rich exhaust codes.

Some automobile manufacturers use a fused circuit to supply voltage to the HO2S system. Test these fuses using the DVOM.

If all fuses are in good working order, locate the HO2S for engine bank one. The vehicle will need to be raised on an appropriate hoist or lifted and secured on safety stands. Once you have accessed the sensor in question, disconnect the harness connector and turn the ignition key to the ON position. You are looking for battery voltage at the HO2S connector. Use the wiring schematic to determine the circuit used to supply battery voltage. Also check the system ground at this point.

If HO2S voltage and ground are present, reconnect the HO2S. Start the engine and test-drive the vehicle. After a test drive, let the engine idle (with the transmission in neutral or park). Use the scanner to observe the HO2S input data. Limit the data stream scope to include only relevant data, and you will get a faster data response. Assuming the engine is running efficiently, the upstream HO2S should regularly switch from rich to lean (and vice versa) with the PCM in closed loop.

Unlike most other codes, P064E is likely caused by a faulty controller or a controller programming error
Test the system ground integrity by connecting the DVOM’s negative test lead to ground and the positive test lead to battery voltage

What Does It Mean?

This is a generic diagnostic trouble code (DTC) and applies to many OBD-II vehicles (1996-newer). This may include, but is not limited to, Acura, Audi, Buick, Cadillac, Chevrolet, Chrysler, Ford, Hyundai, Jaguar, Kia, Nissan, Scion, Toyota vehicles, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

A stored code P064F means that the Powertrain Control Module (PCM) has detected an unauthorized or unrecognized software application or a controller calibration error.

Installing factory software and calibrating onboard controllers is often referred to as programming. While most programming is done before the vehicle is delivered to the owner, the onboard controllers continue to adapt to specific circumstances and learn effectively to meet the needs of individual drivers and geographic locations (among others). Factors including voltage spikes, excessive temperatures, and excessive humidity can contribute to software and calibration failure.

Installing aftermarket software may result in a P064F code being stored, but it is usually temporary. Once the PCM has learned the software and the code is cleared, it typically does not reset.

Whenever the ignition is turned on and the PCM is powered, several controller self-tests are performed. By performing controller self-tests, the PCM can monitor serial data that is carried on the Controller Area Network (CAN) to ensure that the onboard controllers interface correctly. Memory functions, as well as software applications, are tested at this time and also tested periodically when the ignition is in the ON position.

If a problem is detected in the monitoring controller’s software/calibration, a P064F code will be stored and a Malfunction Indicator Lamp (MIL) may be illuminated.

A typical Powertrain Control Module PCM, opened:

Powertrain Control Module P064F
How Severe Is This DTC?

A P064F should be considered severe as it can lead to various engine starting and/or driving problems.
What are some of the symptoms of the code?

Symptoms of a P064F trouble code may include:

Engine crank no start or delayed start
Engine driveability issues
Other stored codes

What are some of the common causes of the code?

Causes

of this code may include:

PCM programming error
Faulty controller or PCM
Installation of aftermarket or high-performance software

What are the P064F troubleshooting steps?

Even for the most experienced and well-equipped technician, a P064F code can be particularly difficult to diagnose. Without access to reprogramming equipment, an accurate diagnosis will be virtually impossible.

Consult your vehicle’s information source for Technical Service Bulletins (TSBs) that reproduce the stored code, the vehicle (year, make, model, and engine), and the symptoms presented. If you find the appropriate TSB, it may provide helpful diagnostic information.

Start by connecting the scanner to the vehicle’s diagnostic port and retrieving all stored codes and freeze frame data. You will want to note this information, just in case the code proves to be intermittent.

After recording all relevant information, clear the codes and test drive the vehicle (if possible) until the code resets or the PCM enters readiness mode.

If the PCM enters readiness mode, the code is intermittent and will be even more difficult to diagnose. The condition that caused the P064F to be stored may need to worsen before an accurate diagnosis can be reached. On the other hand, if the code does not reset and no driveability symptoms manifest, the vehicle may be operating normally.

Test the controller ground integrity by connecting the DVOM’s negative test lead to ground and the positive test lead to battery voltage