What it means
The reductant control module power relay control circuit is open or has an open-circuit fault. The code does not establish that the module loses power or fails to wake.
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 lets the vehicle command the relay that supplies power to the reductant control module. This code sets when the control path is detected as open; it does not by itself prove the module has lost power or failed to wake.
Common causes
Most likely first.
- Relay coil open
- Pin pushed back out of connector body
- Cracked solder joint inside the module or sensor
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 whether the control module communicates and reports relay command status.
- Inspect the power relay control connector and harness for backed-out pins, corrosion, broken wires, or damage that could interrupt the command path.
- Check the relay coil and control-circuit continuity with power isolated as directed, comparing results with the manufacturer's specification.
- If the relay coil is intact, test the control wire between the relay and module for an open, including intermittent breaks that appear when the harness is moved gently.
- Check module connector terminals and module-side control operation using the manufacturer's diagnostic procedure before attributing the fault to the module.
Common fixes
- Reseat or repair a loose, backed-out, or corroded relay-control terminal.
- Repair an open or damaged wire in the module power relay control circuit.
- Replace the relay if its coil is confirmed open.
- Repair a confirmed module connector or internal control connection fault according to the manufacturer's procedure.
Can I keep driving?
If the engine runs normally, the vehicle may remain driveable, but reductant-system functions and emissions monitoring may be affected. An active emissions warning can progress to a no-start countdown; heed any countdown and arrange diagnosis promptly.
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.