P21C3

Reductant Heater Relay Control Circuit Low

Severity

⚠️ Medium

Can you drive?

Yes, but get it checked soon

Approx. repair cost

$9–39 (est.)

Symptoms

Check Engine light comes on
Reduced efficiency of the SCR system
Possible increase in NOx emissions
In some cases - limiting engine power
AdBlue system error message on the dashboard

Causes

Open or short circuit in heater relay circuit
Faulty reagent heater relay
Connection problems or connector corrosion
SCR control unit malfunction
Wiring Harness Problems

How to Fix

Check fuses associated with the SCR system
Inspect the wiring and connectors of the heater relay circuit
Check the resistance and operation of the heater relay
Scan the system for additional trouble codes
Replace the reagent heater relay if necessary.

Related codes

P21C1 P21C2 P21C4