P064C — Glow Plug Control Module #

The description of DTC P064C may differ depending on the vehicle manufacturer (OEM). Always verify with official sources for your specific make and model.

• Glow Plug Control Module Control Circuit / Performance (General, Ford, GM, Chrysler)
• Glow Plug Module – Circuit Performance (Mercedes-Benz)
• Glow Plug System Control Module – Signal Fault (Volkswagen, Audi)

Summary of the P064C Code #

P064C is a diagnostic trouble code (DTC) that indicates an issue with the Glow Plug Control Module—the electronic unit responsible for managing the operation of glow plugs in diesel engines. Glow plugs are heating elements that help start diesel engines, especially in cold conditions. When the Engine Control Module (ECM)—also known as the Powertrain Control Module (PCM)—detects a malfunction or abnormal signal from the glow plug control circuit, it sets the P064C code and usually triggers the check engine light. This warning means the system may not be heating the glow plugs properly, potentially affecting cold starts and engine performance. While this code is specific to diesel engines, the underlying causes and symptoms are similar across many OEMs.

Common Symptoms for Code P064C #

When P064C is present, most drivers will notice issues related to starting or running a diesel engine, especially in colder climates. These symptoms may appear suddenly or gradually worsen over time.

• Hard starting in cold weather
• Engine misfires during initial start-up
• Rough idle after cold starts
• Illuminated check engine light
• Temporary reduction in engine performance
• Increased white or gray exhaust smoke at start-up

Probable Causes of Code P064C (By Frequency) #

The most frequent causes of P064C stem from electrical faults, component failures, or wiring issues affecting the glow plug control system. Identifying the exact cause requires systematic testing, but the following list covers the most common culprits in order of likelihood:

1. Faulty glow plug control module (internal failure or corrosion)
2. Damaged or loose wiring/connectors in the glow plug circuit
3. Blown fuses or relays related to the glow plug system
4. Failed glow plugs drawing excessive current
5. Faulty engine control module (ECM/PCM) (rare)
6. Poor ground connections or battery voltage supply issues

Step-by-Step Diagnostic for Code P064C #

A systematic approach is essential to accurately diagnose P064C and avoid unnecessary parts replacement. Follow these steps for a thorough investigation:

• Verify the code with a professional-grade scan tool and check for related DTCs (especially glow plug or glow plug circuit faults).
• Visually inspect the glow plug control module and all associated wiring/connectors for damage, corrosion, or loose connections.
• Test the fuses and relays linked to the glow plug circuit for continuity and correct operation.
• Check the glow plugs for proper resistance and signs of failure (a failed plug can overload the module).
• Measure voltage at the glow plug control module input and output terminals; compare to OEM specifications.
• If no issues are found, use a scan tool to monitor live data from the module; look for abnormal readings or activity during cold start.
• As a last resort, verify the ECM/PCM operation and reprogram or replace if all other components check out.

Possible Repairs for Code P064C #

Once the root cause is identified, repair should directly address the faulty part or connection. Here are the most effective fixes, linked to their corresponding causes:

• Replace the glow plug control module if it is internally faulty or corroded.
• Repair or replace damaged wiring/connectors in the glow plug circuit.
• Replace blown fuses or faulty relays associated with the glow plug system.
• Replace failed glow plugs if they are drawing too much current or are open circuit.
• Clean and tighten all ground points and battery connections.
• Reprogram or replace the ECM/PCM only if all other steps fail and it is confirmed defective (rarely needed).

Is It Safe to Drive with Code P064C? #

Limited: Driving with code P064C is generally not recommended long-term, especially in cold weather. While the vehicle may still start and run in mild conditions, you risk hard starting, poor performance, and increased emissions. In freezing temperatures, the engine may fail to start altogether. Addressing the issue promptly prevents further engine or electrical damage and ensures reliable operation.

Vehicles Most Commonly Affected by Code P064C #

P064C is seen most often on modern diesel-powered vehicles from the following manufacturers, though it can appear on any diesel with electronic glow plug control:

• Ford (F-Series Super Duty, Transit, Ranger Diesel)
• General Motors (Chevrolet Silverado/GMC Sierra Duramax Diesel)
• Ram (2500/3500 Cummins models)
• Volkswagen and Audi (TDI models)
• Mercedes-Benz (Sprinter, Bluetec diesels)
• BMW (diesel variants)

Common Mistakes & Best Practices for P064C #

Technicians and DIYers often misdiagnose this code due to overlooked wiring issues or by replacing parts unnecessarily. Keep these tips in mind to avoid common pitfalls:

• Don’t replace the glow plug control module before checking all wiring and connections.
• Avoid ignoring blown fuses or relays—they may indicate an underlying short or overcurrent issue.
• Always use a scan tool to monitor live data and related codes for a complete picture.
• Test each glow plug individually rather than assuming all are good or bad.
• Consult OEM wiring diagrams and follow the correct pinout during diagnostics.

Express FAQ: P064C Glow Plug Control Module #

Still have questions? Here are quick answers to the most frequent concerns:

• Q: Can a weak battery trigger P064C?
  A: Yes, low voltage can cause glow plug module errors. Always check battery health during diagnostics.
• Q: Will clearing the code fix the problem?
  A: No, clearing the code resets the warning but doesn’t solve the underlying issue. The code will return if the problem persists.