P24D2 code meaning
Reductant Heater A Sense Circuit
Powertrain system Generic code P24xx codes Check engine light
What P24D2 means
Besides the control output, many DEF heaters have a sense line on which the controller reads back the voltage actually reaching the element. P24D2 marks a general fault on this sense circuit for heater A, such as an open lead or a reading that makes no sense at all, as opposed to the voltage being merely too low (P248A) or too high (P248B). GM and Ford call heater A the tank heater. No manufacturer documents P24D2 publicly. GM's 2016 to 2018 diesel tables show the related sense test: system voltage minus heater supply must not exceed 3 V while heating is commanded, judged over 10 of 12 samples at 500 ms. CARB requires SCR heaters and their circuits to be monitored. If the sense signal is lost, the controller cannot confirm thawing, so dosing in frost may stay off.
P24D2 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P24D2
- Malfunction indicator lamp on
- DEF warnings in cold weather, dosing delayed after a cold start
Common causes of P24D2
- Most likelyBroken or disconnected sense wire to heater A
- PossibleDEF creep or water corroding the heater connector
- Less likelyFaulty measuring input in the SCR or engine control module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Reductant heater a
What each part of P24D2 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). |
| D2 | The exact fault in that area. |
What to do next
- Note P24D2 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 P24D2
What does P24D2 mean?
P24D2 means "Reductant Heater A Sense Circuit". Besides the control output, many DEF heaters have a sense line on which the controller reads back the voltage actually reaching the element. It is a generic code, so it means the same on every make.
Is it safe to drive with P24D2?
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 P24D2 fail an emissions test?
Yes, it can. P24D2 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 P24D2 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P24D2 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.