Powertrain, generic · Auxiliary emission controls

P04AB EVAP System Purge Control Valve B Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

The evaporative emission (EVAP) system stores fuel vapour from the tank in a charcoal canister; a purge valve lets the engine draw it off, and a vent valve opens the canister to fresh air. Purge valve B is a second electric purge valve, usually for the high-load purge line of a turbo engine, which purges to the compressor inlet when there is boost in the manifold (Ford patent). Many makers solve this path with one purge valve and passive check valves instead – Ford tests it as P04F0 – and then have no valve B. CARB requires every purge path to be checked. P04AB means the control circuit of purge valve B is open; the high-load path then does not purge. No manufacturer document available to us uses this code; the description follows CARB and the comparable purge valve A checks (for GM P0443/P0458/P0459).

Likely causes

Purge valve B connector loose or corroded
Coil of purge valve B open
Supply (fuse, main relay) or control wire open
Driver in the engine module

Symptoms

  • Check engine light on
  • EVAP readiness not set
  • Usually no change in driving

Repair estimate

DifficultyEasyDIY possible
Parts and labour€40–250
Time0.3–1.5 h

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

Parts involved

evap purge valve bhigh load purge linepurge valve wiringengine control module

Related codes

P04ACP04ADP04AEP04AFP0443P04F0

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