Powertrain, generic (extended)

P204D Reductant Pressure Sensor Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P204D is the high-side counterpart: the pressure signal sits near or above the supply voltage, typically because the signal wire touches 5 V or battery voltage, the sensor ground is open, or the sensor has failed internally. Published limits are 4.80 V on GM's 6.6 L LML, 98 % of the supply in GM's 2018 diesel table, 4.90 V in GM's 2025 DEF controller and 4.85 V on Ford's 2023 diesels. GM's 2014 Cruze diesel logs it as Type B, the other GM tables as Type A. Deutz's EMR L1 calls the same state a short circuit to battery. To the controller such a reading could look like over-pressure, which is why it stops the pump; check the connector at the pump module and the sensor ground before replacing the module.

Likely causes

Open sensor ground or corroded ground terminal
Signal wire shorted to 5 V reference or battery voltage
Internal failure of the pressure sensor in the pump module

Symptoms

  • MIL on (after two trips on some GM diesels)
  • DEF pump stopped, no dosing
  • DEF warning and later inducement

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–1,200
Time0.5–3 h

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

Parts involved

reductant pressure sensor

Related codes

P204AP204CP204BP204E

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