P04AC — EVAP System Purge Control Valve B Circuit Low

P04AC: EVAP System Purge Control Valve B Circuit Low — what it means, the affected system and what to check before replacing parts.

Meaning, symptoms, causes and checks

An abnormally low electrical level is reported in the control circuit for EVAP purge valve B. It is not a direct measurement of a low purge-gas flow.

Affected system: Powertrain

Symptoms

  • Warning light may illuminate
  • Related system function may be impaired
  • Vehicle-specific symptoms vary

Possible causes

  • Exhaust or emissions plumbing leak, restriction, valve fault, sensor fault, or damaged wiring
  • Related wiring, connector, power or ground fault
  • Vehicle-specific mechanical or control issue

What to check

  • Record stored and pending codes and freeze-frame data
  • Inspect the relevant exhaust or emissions plumbing and electrical connections, then compare commanded operation with sensor feedback during the enable conditions.
  • Confirm measured values against the vehicle service information
  • Retest under the conditions that set the code
  • Inspect the relevant exhaust or emissions plumbing and electrical connections, then compare commanded operation with sensor feedback during the enable conditions.
  • Repair the verified cause and confirm the code does not return

Also written as: P04AC-00, P04AC00, PO4AC (some scan tools add the fault-type byte, e.g. -00).