OBD-II code · Network (extended)
U356E Anode Drain Valve Heater Relay Control Circuit
Anode Drain Valve Heater Relay Control Circuit: the control circuit has an electrical fault.
Is it safe to drive with U356E?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyHeater relay failed
- Less likelyGateway module routing CAN messages incorrectly
- Less likelyCAN terminating resistor (120 Ω) drifted out of spec
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.5–2 h
- Emissions test
- Usually unaffected
- Parts involved
- Anode Drain Heater Relay, Relay Wiring
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.