P064C code meaning
Glow Plug Control Module 1
Powertrain system Generic code P06xx codes Check engine light
What P064C means
On diesels a glow plug control module switches the glow plugs (at Ford also the DEF heaters) with semiconductor switches, diagnoses itself and reports to the engine module. P064C means this module reports an internal fault. GM's 2017–18 Duramax checks for a switch that is commanded on but delivers less than 3.2 A and 0 V at the plug (3.5 s), ROM, RAM and EEPROM checksums, the charge pump of the high-side drivers and reverse polarity; the LML (2011–16) used under 6.6 A for 75 % of 4 s; lamp after two trips. Ford's 2023 diesels flag drivers that do not switch or overheat, a RAM checksum error, supply below 6.5 or above 16.5 V and module temperature above 125 °C, within about 1 s. The glow system then fails partly or completely: hard cold starts, white smoke and higher cold-start emissions.
P064C at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of P064C
- Check engine and glow plug lamp
- Hard cold start, long cranking in cold weather
- White smoke and rough running after a cold start
- Glow plug circuit codes as well
Common causes of P064C
- Most likelyGlow plug module faulty internally (switches, memory)
- PossibleInsufficient supply or ground (battery, corrosion, main fuse)
- PossibleShort in a glow plug or wire overloading a driver
- Less likelyMoisture or corrosion in the connector of the engine-mounted module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Glow plug control moduleGlow plugsModule power supply
What each part of P064C means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 6 | Area: computer (engine control module) and output circuits. |
| 4C | The exact fault in that area. |
What to do next
- Note P064C and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P064C
What does P064C mean?
P064C means "Glow Plug Control Module 1". On diesels a glow plug control module switches the glow plugs (at Ford also the DEF heaters) with semiconductor switches, diagnoses itself and reports to the engine module. It is a generic code, so it means the same on every make.
Is it safe to drive with P064C?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P064C fail an emissions test?
Yes, it can. P064C is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P064C to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P064C clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.