A 2019 Ford Tourneo Custom I rolled into a Swedish workshop recently with a single complaint: the check engine light was on, and the only stored code was P24C6. The technician noted nothing else on the job card. This specific code points to a problem with the temperature sensor circuit within the particulate matter sensor. This component monitors the efficiency of the diesel particulate filter. When the engine control module cannot get accurate temperature data, it prevents the sensor from functioning properly and can halt DPF regeneration entirely.
Assessing internal sensor failure
When we ran this through the diagnostic platform we build, an internal failure of the PM sensor ranked as the most likely cause at 85 percent probability. The sensor relies on an internal thermistor to measure temperature and a heating element to reach its optimal operating state. An open or infinite resistance reading across the sensor terminals usually confirms that the internal circuitry has failed. The replacement cost for a new sensor is roughly 300 GBP, or about 4000 SEK. To prove this is the fault, the technician needs to perform a resistance check on the sensor itself and monitor the live data for the PM sensor temperature to see if the values are frozen, implausible, or missing entirely.
Evaluating wiring and connector integrity
Ranked closely behind at 75 percent probability was a wiring or connector issue. The PM sensor lives in the exhaust system, meaning its wiring harness and connector endure extreme heat, constant vibration, and moisture exposure. This harsh environment routinely degrades wire insulation, corrodes contact pins, and creates open circuits or high resistance. A short to ground or to the battery will also disrupt the temperature data transmission and the power supply to the heater element. The required diagnostic steps here are a thorough visual inspection of the harness where it routes near hot components, followed by continuity and resistance checks of the wires back to the control module.
Checking the heater power supply
The sensor cannot reach operating temperature without its internal heater, and that heater requires a reliable power supply. A blown fuse or a faulty relay for the heater circuit was identified as a 60 percent probability cause. If the module does not see the expected temperature rise because the heater has no power, it triggers P24C6. While replacing a blown fuse is straightforward, it is critical to verify if an underlying short circuit caused the fuse to blow in the first place. The correct approach is to check the relevant fuses and relays, then measure for correct voltage directly at the PM sensor connector with the system active.
Ruling out physical exhaust leaks
The final ranked cause, sitting at a 30 percent probability, was an exhaust leak near the sensor. While this is not an electrical fault, escaping exhaust gases alter the thermal environment around the sensor. This can introduce cold air or disrupt the gas flow, creating thermal stress on the electronic components and causing the sensor to report erratic temperature values. The module interprets these physical anomalies as a circuit malfunction. A visual inspection for soot trails around joints or a smoke test of the exhaust system will confirm or eliminate this variable.
Closing the loop on P24C6
Working through these four causes in order allows a technician to isolate the fault without firing parts at the vehicle. Are you seeing similar failure patterns with PM sensors on this generation of Tourneo Custom in your own bays?
Reference pages for the codes in this article
- P24C6, what we measure for this code across real diagnostics