U0646
Lost Communication With Motor Electronics Coolant Pump A
U0646 is an OBD-II diagnostic trouble code meaning: Lost Communication With Motor Electronics Coolant Pump A. Common causes: open or short circuit in wiring harness, electronic coolant pump malfunction. Estimated repair cost: $167–500.
Symptoms
- Engine overheating
- Reduced engine power
- Check Engine Light Is On
- Unstable operation of the cooling system
- Coolant pump noise
Causes
- Open or short circuit in wiring harness
- Electronic coolant pump malfunction
- Problems with connection connectors
- Malfunction of the engine control unit (ECU)
- Poor pump grounding
How to Fix
- Check the integrity of the wiring harness to the pump
- Check the pump connection connectors
- Check fuses and pump relays
- Diagnose the coolant pump
- If necessary, replace the electronic pump
Related codes
Error U0646 by Vehicle Brand
FAQ
What does the U0646 code mean?
U0646 is an OBD-II diagnostic trouble code that indicates: Lost Communication With Motor Electronics Coolant Pump A
What causes a U0646 error code?
The most common causes of U0646 include: Open or short circuit in wiring harness; Electronic coolant pump malfunction; Problems with connection connectors; Malfunction of the engine control unit (ECU).
How do I fix a U0646 diagnostic trouble code?
To fix U0646: Check the integrity of the wiring harness to the pump. Check the pump connection connectors. Check fuses and pump relays. For a complete diagnosis, use an OBD-II scanner.
Is it safe to drive with U0646?
Do not drive — repair immediately
How much does it cost to fix U0646?
The estimated repair cost for U0646 is $167–500. Actual cost depends on your vehicle, location, and labor rates.
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