P21C2

Reductant Heater Relay Control Circuit/Open

Severity

⚠️ Medium

Can you drive?

Yes, but get it checked soon

Approx. repair cost

$17–89 (est.)

Symptoms

Check Engine Light Is On
Possible reduction in engine power
Increased NOx emissions
SCR system error message on instrument panel
Problems starting in cold weather (if the reagent is frozen)

Causes

Open or short circuit in wiring harness
Faulty heater relay
Damage to connectors or corrosion of contacts
Problems with the SCR control unit
Malfunction of the heating element itself

How to Fix

Check the integrity of the wiring harness to the heater relay
Check the resistance and operation of the relay
Inspect connectors for corrosion or damage
Check power and ground in the control circuit
If necessary, replace the relay or heating element

Related codes

P21C0 P21C1 P20EE