U02BBLost Communication With EVAP System Purge Pump
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- The purge pump actively pushes fuel vapour from the charcoal canister into the intake, which turbocharged engines need because they often lack intake vacuum. GM fits it to models such as Blazer, Encore GX, XT4 and Silverado 1500 as a separate unit with its own electronics, linked to the ECM by LIN. GM's 2025 engine tables describe U02BB directly: the ECM marks the pump as lost when its response frame has been absent for at least 250 ms, checked once the LIN channel has been active for 3 s at 11 to 18 V; GM rates it Type B, meaning the lamp waits for a second failing trip. Pump failures were common enough that GM extended coverage to 15 years/150,000 miles (N242484740), there with the P146x pump codes. While the pump is mute the canister is not purged and evaporative tests are suspended.
- What you may notice
- Check engine light after two drives
- Further EVAP or purge pump codes stored
- Possible fuel smell; driving itself usually normal
- Likely causes
- LikelyPurge pump electronics failed (known GM failure, extended coverage)
- PossibleLIN wire or pump connector damaged, corroded or unplugged
- PossibleNo supply from the actuator or powertrain relay, poor ground
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €60 – €450
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.