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U0650 Lost Communication With Exhaust Pressure Control Valve A Sensor/Switch

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

The exhaust pressure control valve is a throttle flap in the exhaust that diesels use to raise back pressure and exhaust temperature, for example during warm-up or filter regeneration. In GM's 2025 diesel table 25OBDG04B this flap is called ETV and reports its position by SENT. U0650 is stored when 480 of 600 checks at 6.25 ms intervals find the position protocol steady low or high with outdated data, a message error, or stalled counters, with relay voltage above 11 V and the engine past cranking. Being Type A, it lights the MIL during the first faulty trip. The same table keeps the drive circuit (P0475) and tracking errors above 10 % (P0476) apart; analog sensor faults are P048B to P048F, valve B has U067E.

Likely causes

Wiring at the exhaust flap damaged by heat
Connector at the flap actuator corroded or loose
Position sensor in the flap actuator failed
Engine controller input fault

Symptoms

  • MIL on from the first trip
  • Particulate filter regeneration delayed or blocked
  • Slower warm-up in cold weather

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–800
Time0.5–3 h

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

Parts involved

exhaust pressure valve a sensorvehicle bus wiring

Related codes

U067EP0475P0476P048BP048CP048DP048EP048F

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