P21C9

Reductant Control Module Power Relay/Relays Control Circuit High

Severity

⚠️ Medium

Can you drive?

Yes, but get it checked soon

Approx. repair cost

$17–89 (est.)

Symptoms

Check Engine light comes on
Reduced engine power
Increased fuel consumption
Problems with the SCR system
Possible engine operation restrictions

Causes

Faulty reagent control module relay
Short circuit in control circuit
Wiring harness damage
Problems with the SCR ECU
Corrosion of contacts or connectors

How to Fix

Check the condition of the reagent control module relay
Check the integrity of wiring and connectors
Measure the voltage in the control circuit
Check the operation of the reagent control module
If necessary, replace faulty components

Related codes

P21C8 P21CA P20EE