P21CA

Reductant Control Module Supply Voltage Circuit

Severity

⚠️ Medium

Can you drive?

Yes, but get it checked soon

Approx. repair cost

$56–278 (est.)

Symptoms

Check Engine light comes on
Reducing engine power (limp mode)
Increased fuel consumption
SCR/AdBlue system error message on the dashboard
Unpleasant exhaust smell

Causes

Open or short circuit in the module power supply circuit
Faulty relay or fuse
Problems with wiring harness or contacts
Malfunction of the reducer control module itself
Circuit Grounding Problems

How to Fix

Check the condition of fuses and relays
Inspect the wiring harness for damage
Check the voltage at the module terminals
Test circuit integrity and grounding quality
If necessary, replace the reducer control module

Related codes

P20EE P2201 P229F