P24C9

Code

Generic P — Powertrain

Particulate Matter Sensor Temperature Circuit High

Brand: Generic

Type: P — Powertrain

Views: UK: 22 EN: 205 RU: 38

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Page language: EN

Causes

Open or shorted wiring in the PM sensor temperature circuit
Short to battery/ignition voltage on the temperature signal
Corroded, contaminated, or loose connector at the PM sensor
Failed particulate matter sensor (temperature element)
Poor or missing ground in the sensor circuit
Water intrusion or physical damage to the sensor/harness

Symptoms

Malfunction Indicator Lamp (MIL) or check engine light illuminated
Stored P24C9 (and possibly related) codes in ECM
Reduced or inhibited active regeneration of diesel particulate filter (DPF) control strategies
DPF-related warnings or limp-home behaviors on some vehicles
Failed emissions/inspection tests related to DPF performance

What to check

Read and record all stored codes and freeze-frame data with a scan tool; note conditions when code set
Visually inspect PM sensor, connector, and wiring for damage, corrosion, water, or rodent chew marks
Backprobe the temperature signal connector with ignition ON (engine OFF) and measure signal voltage
Check for obvious short to battery by measuring voltage between signal pin and battery positive with circuit disconnected
Check continuity of the signal and ground conductors from sensor connector to ECM using an ohmmeter
Inspect and test the sensor ground at chassis/ECM ground points

Signal parameters

Typical temperature sensor signal: ~0.2–4.8 V (varies by manufacturer) — “High” condition often >4.5–4.8 V or pegged at battery voltage
Typical thermistor resistance range (example): ~100 Ω to 100 kΩ depending on temperature — consult vehicle-specific data
Scan-tool live data: PM sensor temperature should change sensibly with ambient/engine changes (not jump to max)
No-load open-circuit: infinite resistance (open) will often result in a high or out-of-range voltage reading

Diagnostic algorithm

Connect a capable scan tool; record P24C9 and any related codes; note freeze-frame data and live PM sensor temperature reading.
Perform a visual inspection of sensor, harness, and connector; repair obvious damage before further testing.
With ignition ON (engine OFF) backprobe the signal and ground pins at the PM sensor connector and measure signal voltage. A high voltage near battery (>4.5 V) indicates short to power or open sensor circuit depending on circuit design.
Disconnect the sensor and measure voltage at the harness/connector. If voltage remains high with sensor disconnected, suspect wiring short to battery or ECM pull-up. If voltage drops to expected reference when disconnected, suspect sensor failure.
Measure continuity/resistance of signal and ground wires between sensor connector and ECM; check for short to battery or other circuits with an ohmmeter.
If the sensor is removable, measure its resistance vs. temperature (ambient) and compare to manufacturer specification or expected thermistor behavior. Replace sensor if out of spec.
Perform a wiggle test on the harness with probe monitoring the signal for intermittent faults during vibration or movement.
Repair any damaged wiring, connectors, or grounds. After repair, clear codes and perform drive/regen cycles to confirm the fault does not return.
If wiring and sensor check good and fault persists, test/verify ECM input and replace ECM only after all other causes are eliminated.

Likely causes

Damaged insulation exposing conductor and shorting to power
Disconnected or corroded sensor connector pins
Failed NTC/thermistor or built-in temperature sensor inside PM sensor assembly
Aftertreatment plumbing or mounting allowing water ingress into sensor connector
Faulty ground or harness chafing at suspension/movement points

Fault status

⚠️ Status

Particulate Matter Sensor Temperature Circuit High — temperature signal voltage above expected range; possible short to battery, open sensor element, connector or wiring fault.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1-3 hours