Error Code P064C is defined as Glow Plug Control Module. This is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system. This includes vehicle models from Chrysler, Ford, GMC, Mercedes Benz, etc. Specifications on the definition, troubleshooting, and repairs, of course, vary from make, model, and powertrain configuration.

The job of the glow plug control module is to initiate both the glow plug heater timer and glow plug for every individual cylinder. Vehicles with diesel propulsion system use glow plugs, glow plug timer and glow plug controller.

Error Code P064C means a fault in the glow plug control module has been detected by the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes).

Glow plug control module can be a stand-alone module or integrated to the PCM. Every time the ignition is turned on and the PCM is energized, various controller self-tests are simultaneously performed. Aside from running internal controller self-test, the CAN (controller area network) carries serial data from each module to make sure the onboard controllers are interfacing properly.

If the PCM determines a problem while monitoring the glow plug control module, it will register the Error Code P064C and activate the Check Engine light.

Common Symptoms

Since this code results to lack of glow plug function, the vehicle will experience a no-start condition, classifying this code as a severe problem. Other common symptoms include:

  • Engine stall at startup
  • Delayed engine startup (especially during cold weather)
  • Drivability issues
  • One or more glow plugs are incapacitated

In other cases, other stored codes may be present as well.

Possible Causes

Common causes for this code include:

  • Defective glow plug control
  • Faulty PCM or programming error in PCM
  • Open or shorted glow plug control circuit
  • Open glow plug control module voltage supply circuit

How to Check

Checking this code requires a DVOM (digital volt ohmmeter), dependable vehicle information for TSB (technical service bulletin) that has the code stored, vehicle (year, make, model, engine), and exhibited symptoms. Finding the right TSB can lead you to more easy and successful diagnostic and repair procedure.

Start by connecting the scanner to the vehicle diagnostic port. Retrieve all the stored data including freeze frame data. Write down this information. Then, clear the codes and then take the vehicle for a test drive until the code reset, or the PCM enter readiness mode.

If the PCM enter readiness mode, that means the problem is intermittent. You may have to wait for the problem to get worse before you can successfully diagnose and repair. If the code resets on the other hand, then continue with the diagnosis.

Use the vehicle information to know the connector pin-out charts, face views, component locators, wiring diagrams, and diagnostic flow charts of the vehicle.

Use the diagram and DVOM to check the voltage of the battery on the glow plug control circuit. If there’s none, check the system fuses and relays. Replace the defective parts as necessary.

If there is no voltage (and ground) on the glow plug control circuit (and all fuses and relays look to be working properly), inspect the controller related wiring and harness. Check the chassis and engine ground junctions. Use the vehicle information source to get a ground location for related circuits.

If there is voltage (and ground) present on the glow plug control circuit, then check system controllers and look for signs of damage, water intrusion, heat, or collision damage. Damaged controllers, especially those damaged by water, are considered defective and must be replaced.

If the controller power and ground circuits are in good shape, then you can suspect a defective controller or a programming error. In which case, controller replacement will be required, as well as reprogramming.

In some cases, you may want to purchase a re-programmed controller from aftermarket sources. Other vehicles/controllers require onboard reprogramming that may be done through a dealership, or by a qualified technician.

How to Fix

  • Replacement of glow plug control
  • Repair or replacement of glow plug control circuit
  • Repair or replacement of glow plug control module
  • Replacement and reprogramming of PCM

It’s important to test the integrity of the controller ground by connecting its negative test lead of the DVOM to ground, and a positive test lead to the battery voltage.