U0644Lost Communication With Wastegate Position Sensor A
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- Pneumatic wastegates have largely given way to electric actuators, and these carry a position sensor so the controller knows how far the bypass flap around the turbine is open. GM reads that sensor on charger A over SENT and, in the 2025 table 25OBDG03B, stores U0644 when message faults appear or a frame is older than 3.13 ms in 10 out of 12 samples taken every 100 ms, with relay voltage of at least 11 V and the engine not cranking; it is Type A, so the MIL comes on in the first trip. GM's harness bulletin PIT5677 for the 2.7L L3B in 2019–2021 Silverado and Sierra 1500 lists U0644 among codes caused by a chafed engine harness. Analog faults would be P2AB7 to P2AB9. Expect reduced power.
- What you may notice
- MIL on from the first trip
- Reduced engine power, boost limited
- Several other engine codes when the harness is damaged
- Likely causes
- LikelyEngine harness chafed at brackets or covers
- PossibleConnector at the wastegate actuator loose or corroded
- PossiblePosition sensor in the actuator failed
- RareLow supply voltage or poor ground
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €60 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.