P24B4 code meaning
Particulate Matter Sensor Heater Control Circuit Range/Performance
Powertrain system Generic code P24xx codes Check engine light
What P24B4 means
P24B4 is a plausibility check on the heater of the particulate matter sensor, and makers apply it differently. Ford's 2023 diesel summary looks during measurement, with the heater switched off, and sets the code if heater voltage still exceeds 7 V for 2 s. GM's 14OBDG04 table uses the heater to confirm that exhaust actually reaches the element inside its protection tube: if heater voltage varies by less than 100 % while exhaust velocity is above 30 m/s, the result is a Type B fault. GM's 16OBDG04 instead times how long the heater needs to reach the regeneration setpoint and lists P24B4 as Type X without MIL. A blocked protection tube, a weak heater or extra resistance in the harness can all set it. P24B3, P24B5 and P24B6 cover the pure circuit faults.
P24B4 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of P24B4
- Malfunction indicator lamp on (not with every manufacturer)
- Particulate filter monitor does not complete
Common causes of P24B4
- PossibleProtection tube of the sensor blocked by soot or deposits
- PossibleHeater element aged and heating too slowly
- PossibleExtra resistance in the heater harness
- Less likelyHeater output in the sensor control unit not switching off
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Particulate matter sensor heater
What each part of P24B4 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| B4 | The exact fault in that area. |
What to do next
- Note P24B4 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P24B4
What does P24B4 mean?
P24B4 means "Particulate Matter Sensor Heater Control Circuit Range/Performance". P24B4 is a plausibility check on the heater of the particulate matter sensor, and makers apply it differently. It is a generic code, so it means the same on every make.
Is it safe to drive with P24B4?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P24B4 fail an emissions test?
Yes, it can. P24B4 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P24B4 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P24B4 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.