P21C3: The AdBlue heater relay control gives a lower signal than normal
The AdBlue heater relay control gives a lower signal than normal. It is usually the part, its wiring or a connector with poor contact.
| Code | P21C3 |
|---|---|
| System | Engine and transmission |
| Group | P21xx, Throttle, injection and emissions |
| Type | Generic: it means the same on every make |
How to read and clear P21C3 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P21C3 with its description and whether it’s confirmed, pending or permanent.
If the engine stores it over standard OBD, with FREE you read this code with its explanation for nothing and clear it. With PRO you also read the faults of every control unit and clear them in all of them.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before an inspection. It’s all in how to read and clear fault codes and in inspections and OBD.
Similar codes
- P21BF The cold start cylinder 10 injection timing is not working properly
- P21C0 The cold start cylinder 11 injection timing is not working properly
- P21C1 The cold start cylinder 12 injection timing is not working properly
- P21C2 The AdBlue heater relay control has a broken or disconnected wire
- P21C4 The AdBlue heater relay control gives a higher signal than normal
- P21C5 The AdBlue level sensor A has got stuck
- P21C6 The AdBlue level sensor B has got stuck
- P21CA The AdBlue control unit power supply voltage has an electrical fault
- P2100 Throttle actuator A control motor circuit open
- P2101 Throttle actuator A control motor circuit range or performance
- P2102 Throttle actuator A control motor circuit low
- P2104 Throttle control system: forced idle
What does code P21C3 mean?
The AdBlue heater relay control gives a lower signal than normal. It is usually the part, its wiring or a connector with poor contact.
How do you clear P21C3?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P21C3 comes back.
Read it on your car
Final OBD reads and clears engine faults through standard OBD for free, each one explained in plain English. With PRO it also reads the faults of every control unit, each make’s own codes included, and clears them in all of them.
