Powertrain, generic (extended)

P25BD Unmetered Fuel - Forced Engine Shutdown

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P25BD protects against engine runaway, where the engine keeps speeding up although the controller injects no fuel, for instance because oil from a failed turbocharger seal or combustible vapour drawn into the intake is being burned. GM documents the monitor in its diesel ECM tables. In 14OBDG04 the speed must pass 5,400 rpm for 0.01 s, after which the controller cuts the air supply with its intake air valve and disables the injectors; 18OBDG04 uses 5,500 rpm for 0.5 s and 20OBDG04 5,200 rpm for 0.1 s, both enabled above 1,500 rpm. Each table rates it Type A, so the MIL comes on in the first trip. Unlike P0219, which merely records an overspeed, P25BD means the engine was forcibly stopped. Before a restart, turbo, crankcase ventilation and intake tract should be checked for oil.

Likely causes

Turbocharger seal failure feeding oil into the intake
Oil carry-over from crankcase ventilation, e.g. overfilled or diluted oil
Combustible vapour drawn in from the surroundings
Erroneous engine speed signal or controller fault

Symptoms

  • Engine revs up uncontrollably and then shuts off
  • Heavy smoke from the exhaust before shutdown
  • Check engine lamp on immediately
  • Possible severe engine damage after the event

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€300–8,000
Time2–20 h

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

Parts involved

turbocharger sealsintercoolerintake manifoldair shutoff valve

Related codes

P0219

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com.