What it means
The reductant control module power relay control circuit signal is low. The code alone does not confirm a short to ground; the cause depends on the circuit design.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The reductant control module power relay control circuit carries the vehicle's command for the relay supplying the reductant module. This code sets when the control signal is lower than expected; a ground short is possible, but excess resistance or another circuit-specific fault can also cause the low reading.
Common causes
Most likely first.
- Short to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
How to diagnose it
- Read freeze-frame data and all reductant-system codes, and check module communication and relay command status to establish the conditions when the low signal occurred.
- Inspect the relay control harness and connectors for chafing, exposed conductors, corrosion, moisture, or loose terminals.
- Measure the control signal while commanding the relay with the manufacturer's procedure, comparing it with the manufacturer's specification.
- With power isolated as directed, test the control wire for unwanted continuity to ground and check connector contact resistance.
- If the relay and wiring pass, verify the module control output and connector condition using the manufacturer's diagnostic procedure.
Common fixes
- Clean and secure corroded or loose relay-control terminals.
- Repair chafed wiring or a confirmed short to ground in the control circuit.
- Repair a high-resistance connection or damaged harness section.
- Replace the relay or repair the module-side connection only if testing confirms the fault.
Can I keep driving?
The vehicle may still run, but the reductant control module relay may not be commanded correctly and emissions monitoring can be impaired. A persistent warning can lead to a no-start countdown; heed any countdown and limit use until the circuit is repaired.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.