Powertrain, generic (extended)

P204F Reductant System Performance (Bank 1)

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P204F (Bank 1) is the functional check of the whole DEF delivery path: the parts are electrically intact, yet the system cannot build or hold the pressure needed for dosing. GM's 6.6 L LML stores a Type A code if the pump module stays at or below 350 kPa after 30 build-up and venting attempts of at least 10 s each; the 2014 Cruze diesel uses 375 kPa and 20 attempts. GM treats P204F as a tamper fault. On Hino trucks P204F is the engine ECU's summary code for urea SCR faults seen by the dosing unit; per TT-14-025 it clears only after the DCU faults are repaired and the SCR memory has been reset. Ram's 3.0 L V6 EcoDiesel received PCM updates covering it (18-008-21). CARB demands this delivery check. Causes include frozen or clogged lines, a worn pump, air leaks or an empty tank.

Likely causes

DEF line clogged by crystals or frozen
Worn DEF pump that cannot reach target pressure
Air leak on the suction side or loose line couplings
Dosing unit faults repaired but SCR memory not reset (Hino)
Control module software needing an update (Ram 3.0 L)

Symptoms

  • MIL and DEF warning on
  • Countdown to speed or power limitation
  • Code returns after clearing until the cause is fixed

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–2,500
Time1–6 h

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

Parts involved

reductant pumpreductant pressure sensorreductant linesreductant injection valve

Related codes

P205FP20E8P20E9P202EP208BP218F

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