P21C8

Reductant Control Module Power Relay/Relays Control Circuit Low

Severity

⚠️ Medium

Can you drive?

Yes, but get it checked soon

Approx. repair cost

$28–167 (est.)

Symptoms

Check Engine light comes on
Reduced engine power (in some cases)
Increased NOx emissions
SCR system error message on dashboard
AdBlue system malfunction

Causes

Faulty regenerator module relay
Open or short circuit in control circuit
Poor contact in connectors
Reducer module malfunction
Problems with the engine control unit

How to Fix

Check the regenerator module relay
Inspect the control circuit for damage
Check connections and connectors
Test the reducer module
Check power and ground circuit
If necessary, replace the relay or module

Related codes

P20EE P21C9 P2201