U04A0 code meaning
Invalid Data Received From Engine Coolant Pump Control Module
Network system Generic code U04xx codes Check engine light
What U04A0 means
Engines with an electric main coolant pump carry a pump whose built-in electronics set the speed on request and send back status and fault information. Rheinmetall, for example, builds such pumps for main engine cooling with a LIN interface and extensive self-diagnosis, and Hella notes that electric pumps can stay off after a cold start so the engine warms faster. U04A0 means the engine controller still receives pump messages but finds speed, status or check values implausible. No manufacturer documents this code publicly. It matters for emissions because CARB 1968.2 expects coolant temperature to reach its closed-loop threshold in time, which depends on a correctly controlled pump. U019F and U0672 stand for lost contact. Watch the temperature gauge: the engine may run hot, limit power or keep the fan on.
U04A0 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U04A0
- Check engine or coolant temperature warning
- Engine runs hot or the cooling fan runs continuously
- Reduced engine power to protect the engine
Common causes of U04A0
- Most likelyPump electronics faulty, often after overheating or coolant ingress
- PossibleLIN or CAN wire or connector at the pump corroded or loose
- PossiblePump running dry or blocked (air in system, debris), reported as error state
- Less likelyPump or engine controller software not matched after replacement
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Engine coolant pump module
What each part of U04A0 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| A0 | The exact fault in that area. |
What to do next
- Note U04A0 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 U04A0
What does U04A0 mean?
U04A0 means "Invalid Data Received From Engine Coolant Pump Control Module". Engines with an electric main coolant pump carry a pump whose built-in electronics set the speed on request and send back status and fault information. It is a generic code, so it means the same on every make.
Is it safe to drive with U04A0?
Drive gently and only to a workshop. With U04A0 the car can go into limp mode (reduced power) to protect itself.
Will U04A0 fail an emissions test?
Yes, it can. U04A0 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 U04A0 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will U04A0 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.