P24D2Reductant Heater A Sense Circuit
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- 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.
- What you may notice
- Malfunction indicator lamp on
- DEF warnings in cold weather, dosing delayed after a cold start
- Likely causes
- LikelyBroken or disconnected sense wire to heater A
- PossibleDEF creep or water corroding the heater connector
- RareFaulty measuring input in the SCR or engine control module
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €80 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.