Powertrain, generic (extended)

P24A1 Closed Loop Particulate Filter Regeneration Control At Limit - Temperature Too High

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

Here the regeneration loop has reduced its heat input as far as possible, but the temperature ahead of the filter still runs above target. GM lists P24A1 as the negative-deviation branch of the HC injector control check in steady regeneration, again a Type B fault counted over samples; the 2014 table calls it excessive hydrocarbon injector authority, and the 2018 table shows the check behind a calibration enable flag. Hino bulletin SB-22-007 names P24A1 and P24A2 on 2020 J08 conventional trucks fitted with a certain bubbler fuel filter, fixed by fitting a revised filter. Fuel leaking from a doser or injector, a sensor reading high or an uncontrolled soot burn can cause it. Unlike P24A0 the risk is thermal stress on the filter, so engines may cut the regeneration short.

Likely causes

Hydrocarbon doser or fuel injector leaking extra fuel into the exhaust
Fuel supply part causing unstable doser pressure (Hino 2020 bubbler filter)
Exhaust temperature sensor reading too high
Heavy soot load burning faster than the controller can follow

Symptoms

  • Malfunction indicator lamp on
  • Regeneration aborted early
  • Possible high exhaust temperature warning

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–1,500
Time1–4 h

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

Parts involved

dpf b1

Related codes

P24A0P249FP244DP24A2

References: gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov.