P04AB

What it means

P04AB means the engine control unit has detected an open circuit in the control circuit of the second (B) evaporative emission purge control valve. The control unit monitors the valve's driver circuit and found no current flow or a voltage that shows the circuit is broken. The valve cannot be commanded properly, so fuel vapour purging may not work as intended.

Symptoms

• Check engine light on
• Difficulty starting or long cranking after refuelling
• Rough idle or occasional stumble
• Fuel smell around the car or fuel tank area
• Other EVAP codes stored alongside this one
• Failed emissions test

Possible causes

• Faulty purge control valve B (open internal coil)likely
• Damaged, chafed or broken wiring in the valve control circuitlikely
• Corroded, loose or pushed-out pins in the valve connectorlikely
• Open circuit in the power supply or fuse feeding the valvepossible
• Poor earth or driver circuit fault at the engine control unit connectorpossible
• Internal driver fault in the engine control unitrare

How to diagnose

1. Read all stored and pending codes and note the freeze frame data, including engine temperature and load when the fault set.
2. Check the vehicle documentation to identify which valve is 'B' on this engine, as the location varies by model and engine.
3. Visually inspect the valve, its connector and the wiring run for chafing, heat damage, corrosion or rodent damage.
4. Disconnect the valve and measure its coil resistance, comparing it with the manufacturer's specification; an infinite reading indicates an open coil.
5. With the connector unplugged and ignition on, check for supply voltage and a good earth or driver signal at the harness side.
6. Perform a wiring continuity test between the valve connector and the engine control unit, and check for shorts to earth or supply.
7. Use a scan tool's actuator test to command the valve and listen or feel for clicking, if supported.
8. Check the relevant fuse and relay for the valve supply, if fitted.

How to fix

• Replace the purge control valve B if its coil is open or it fails the actuator test.
• Repair or replace damaged wiring between the valve and the engine control unit.
• Clean or repair the connector terminals, or replace the connector if the pins are damaged.
• Replace a blown fuse only after finding out why it failed.
• Repair the supply or earth fault found in the circuit.
• If all wiring and the valve test good, have the engine control unit driver circuit diagnosed and repaired or replaced as needed.

Can I keep driving?

Nearby codes

• P04AAGenericExhaust Pressure Control Valve B Position Sensor/Switch Circuit Intermittent/Erratic
• P04ACGenericEVAP System Purge Control Valve B Circuit Low