U0325 code meaning
Software Incompatibility With Auxiliary Heater Control Module
What U0325 means
The auxiliary heater control module runs an extra heat source: a fuel-burning or electric coolant heater, or on electrified cars a high-voltage heater that warms the cabin while the engine is off. U0325 means a connected module rejects this unit's software. No manufacturer documents U0325 publicly. GM's 2013–2014 Volt shows the role: its coolant heater control module provides cabin heat in electric mode, and without it heat only comes once the engine runs (PIC5943). BMW shows that heater software can reach into OBD: on i3 and i8 the MIL came on with fault 8013A3, a low reading of the high-voltage heater's OBD coolant temperature sensor, although heating worked; BMW blamed the climate control software and reprogrammed the car (SI B12 21 16). U0166 is lost contact, U0425 invalid data. Expect missing heat.
U0325 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyWorkshop only
- Typical labor0.5 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0325
- No auxiliary or parking heat, cabin warms only with the engine running
- Heater warning or service message
- On plug-in hybrids the engine starts more often for heat
Common causes of U0325
- Most likelyHeater unit or its controller replaced without programming or coding
- PossibleClimate or vehicle software level does not match the heater variant
- PossibleRetrofitted parking heater not coded into the vehicle network
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Auxiliary heaterControl module software
What each part of U0325 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 25 | The exact fault in that area. |
What to do next
- Note U0325 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 U0325
What does U0325 mean?
U0325 means "Software Incompatibility With Auxiliary Heater Control Module". The auxiliary heater control module runs an extra heat source: a fuel-burning or electric coolant heater, or on electrified cars a high-voltage heater that warms the cabin while the engine is off. It is a generic code, so it means the same on every make.
Is it safe to drive with U0325?
U0325 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U0325 fail an emissions test?
U0325 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U0325 to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will U0325 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.