What it means
NOx sensor C (smart sensor with own ECU) received implausible data from the ECM/PCM. Engine load, fuel rate or temperature data needed for the sensor's internal compensation fails plausibility checks; the sensor reports degraded readings.
At a glance
- Usually lights the warning light of the system that lost communication
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
NOx sensor C has its own control unit and needs ECM/PCM information, including engine load, fuel rate, and temperature, to compensate its exhaust measurement. This code sets when the sensor's control unit judges that compensation data from the ECM/PCM implausible, so it reports degraded NOx readings.
Common causes
Most likely first.
- ECM/PCM internal fault or sensor input drift
- Software version mismatch after replacement
- Gateway module routing CAN messages incorrectly
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
How to diagnose it
- Save freeze-frame data and scan all modules for ECM/PCM, NOx sensor C, and network codes to see when the invalid compensation data appeared.
- Compare live engine load, fuel rate, and temperature values sent by the ECM/PCM with available engine data and check for missing or implausible values.
- Inspect the ECM/PCM and NOx sensor C connectors, sensor harness, and CAN wiring for heat damage, corrosion, loose pins, or poor grounds.
- Look for engine sensor or input faults that could cause incorrect load, fuel-rate, or temperature messages.
- Confirm compatible software and configuration for the ECM/PCM, NOx sensor C, and gateway, especially after any replacement or programming.
- If inputs, wiring, and configuration check out, use manufacturer-approved network tests to isolate the ECM/PCM, sensor control unit, or gateway.
Common fixes
- Repair damaged or corroded NOx sensor C, ECM/PCM, or CAN wiring and connectors.
- Fix the underlying engine sensor or input fault that is making compensation data implausible.
- Correct software or configuration mismatches between NOx sensor C, ECM/PCM, and gateway.
- Replace the confirmed faulty ECM/PCM, NOx sensor C control unit, or gateway.
Can I keep driving?
Limit driving and arrange diagnosis soon because degraded NOx readings can impair emissions control and may cause power restrictions or limp mode. Avoid heavy loads, and stop if the vehicle loses power or displays a serious exhaust-system warning.
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.