Network, generic

U02BB Lost Communication With EVAP System Purge Pump

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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.

Likely causes

Purge pump electronics failed (known GM failure, extended coverage)
LIN wire or pump connector damaged, corroded or unplugged
No supply from the actuator or powertrain relay, poor ground

Symptoms

  • Check engine light after two drives
  • Further EVAP or purge pump codes stored
  • Possible fuel smell; driving itself usually normal

Repair estimate

DifficultyMediumDIY possible
Parts and labour€60–450
Time0.5–1.5 h

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

Parts involved

evap purge pumpvehicle bus wiring

Related codes

P0441P0496P0455

References: gsi.ext.gm.com, static.nhtsa.gov, static.nhtsa.gov, law.cornell.edu.