P24C9Particulate Matter Sensor Temperature Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- P24C9 reports the PM sensor temperature reading stuck at the high end, which GM explains as a short toward supply voltage or a broken meander line. In GM's 25OBDG04A diesel table the sensor control unit checks the meander signal and its reference: a signal under 0.3 V or over 3.5 V, or a reference under 4.5 V, counts as a failure, and 24 failures in a row or 24 of 96 samples set a Type B code with two trips. Other makers reviewed here, such as Ford in its 2023 diesel summary, report out-of-range temperature signals under P24C6 instead. A broken pigtail lead near the hot sensor body is a common cause. While the temperature is invalid the heater control and the filter monitor are suspended. P24C8 is the low side, P24C7 the plausibility test.
- What you may notice
- Malfunction indicator lamp on
- Particulate filter monitor does not complete
- Likely causes
- LikelyBroken temperature lead near the sensor body
- PossibleTemperature line shorted to a voltage source
- RareReference voltage of the temperature circuit too low
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €100 – €700
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.