Powertrain, generic (extended)

P24D2 Reductant Heater A Sense Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

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.

Likely causes

Broken or disconnected sense wire to heater A
DEF creep or water corroding the heater connector
Faulty measuring input in the SCR or engine control module

Symptoms

  • Malfunction indicator lamp on
  • DEF warnings in cold weather, dosing delayed after a cold start

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–900
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

reductant heater a

Related codes

P24D3P248AP248BP20B9

References: gsi.ext.gm.com, fordservicecontent.com, law.cornell.edu.