Powertrain, generic (extended)

P204E Reductant Pressure Sensor Circuit Intermittent/Erratic

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P204E covers a DEF pressure signal that jumps around although it stays inside the electrical limits, as with a loose terminal, a cracked wire or a sensor with an internal contact problem. GM's 2025 DEF controller is the public calibration: it adds up all absolute pressure changes over a moving window of 100 readings taken every 10 ms and counts a failure when that sum passes 1500 kPa while pumping forward, 1000 kPa when stopped or heating, or 200 kPa in reverse; ten failures within 100 runs store a Type A code. No other manufacturer documents the code in public. CARB expects input components to be checked for implausible as well as out-of-range signals. Besides the wiring, air in the line or a pump delivering unevenly can also make the pressure swing.

Likely causes

Loose or fretted terminal at the pressure sensor connector
Wire breaking intermittently under vibration
Air in the DEF line or uneven pump delivery
Pressure sensor with internal intermittent fault

Symptoms

  • MIL on, fault may come and go
  • Dosing interrupted at times
  • Accompanying DEF pump or pressure codes

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–1,200
Time0.5–3 h

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

Parts involved

reductant pressure sensor

Related codes

P204AP204BP204CP204D

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