Faulty glow plug control module (internal failure or overheated output stage); Wiring or connector faults at the module, such as corrosion, loose pins or damaged wires; Poor power or earth supply to the module, including a corroded battery terminal or fuse problem; Shorted or failed glow plugs overloading the module; Communication fault between the module and the engine control unit (data line fault); Low battery voltage or a weak charging system; Outdated or faulty software in the engine control unit or glow plug module, where the manufacturer has issued a fix.

P064C

Glow Plug Control Module 1.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
6: AreaComputer and output circuits
4C: FaultThe specific fault in that area

What it means

P064C is a generic powertrain code relating to the glow plug control module on diesel engines. It is set when the engine control unit detects a fault within the glow plug control module itself, such as an internal failure, a performance problem, or a communication or supply issue. The exact test that sets the code varies by manufacturer and engine, so check the model-specific information.

Symptoms

Hard or extended cranking on cold starts
White or grey smoke at start-up while the engine is cold
Rough running or misfire until the engine warms up
Glow plug warning light on or flashing, or engine management light on
Engine running in a reduced-performance mode
Increased diesel knock when cold

Possible causes

Faulty glow plug control module (internal failure or overheated output stage)likely
Wiring or connector faults at the module, such as corrosion, loose pins or damaged wireslikely
Poor power or earth supply to the module, including a corroded battery terminal or fuse problempossible
Shorted or failed glow plugs overloading the modulepossible
Communication fault between the module and the engine control unit (data line fault)possible
Low battery voltage or a weak charging systempossible
Outdated or faulty software in the engine control unit or glow plug module, where the manufacturer has issued a fixrare

How to diagnose

Read all stored and pending codes and the freeze frame data, noting coolant temperature and battery voltage when the code set
Check for other glow plug codes (individual plug circuit or heater faults) and any communication codes, as these point to the root cause
Visually inspect the module, its connector, wiring and fuses for damage, heat marks, water ingress or corrosion
Test battery condition and charging voltage, then check the module's power and earth supply under load
Measure the resistance of each glow plug and check current draw against the manufacturer's specification
Check the communication line between the module and engine control unit for continuity and shorts
Use a scan tool to command the glow plug system and watch the module's response and live data
Check for manufacturer service bulletins or software updates relevant to the model and engine

How to fix

Repair or replace damaged wiring, connectors or terminals, and clean the earth points
Replace the glow plug control module if it has failed internally, and code or adapt it if the vehicle requires
Replace any failed or shorted glow plugs, as they can damage a new module if left in place
Restore a good power supply by repairing the battery connections, fuses or charging system
Repair the data line fault between the module and the engine control unit
Apply a manufacturer software update only if a known calibration fault applies to the vehicle

Can I keep driving?

Medium severity

The car can usually be driven short-term, but cold starting may be poor and the engine may run in a reduced mode. Get it fixed soon, as a failing module or shorted glow plugs can leave the car hard to start in cold weather.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.