What Does P042F Mean?
The PCM has determined that the EGR valve 'A' is stuck in the closed position and not flowing exhaust gas when commanded. This results in elevated combustion temperatures and increased NOx emissions. The driver may notice pinging/detonation under load, and the MIL will be illuminated. Performance symptoms are typically less noticeable than a stuck-open condition.
Common Causes
35%
Carbon buildup sealing the EGR valve shut
30%
Failed EGR valve (mechanical binding or stuck pintle)
15%
Clogged EGR passages in the intake manifold restricting flow
12%
EGR solenoid or actuator not receiving command signal
8%
Blocked or disconnected vacuum supply (vacuum-operated systems)
Diagnostic Steps
1
Command the EGR valve open to 50% via the scan tool's bi-directional controls and observe the actual position — if it remains at 0%, the valve or actuator has failed.
2
Remove the EGR valve and inspect the pintle seat and EGR port for heavy carbon buildup. Probe the EGR passages in the intake manifold with a wire to check for blockage.
3
With the valve removed, apply direct vacuum (vacuum-type) or 12V command (electronic-type) and verify the valve opens smoothly against spring pressure.
4
On electronic EGR systems, verify the actuator motor receives the commanded voltage/duty cycle from the PCM — use a multimeter on the control wires while commanding the valve open.
5
Check the EGR position sensor feedback signal for proper operation — it should smoothly track from closed to open voltage as the valve is manually actuated.
Estimated Repair Cost
$150 - $550
Parts + labor, varies by vehicle and location
The PCM has determined that the EGR valve 'A' is stuck in the closed position and not flowing exhaust gas when commanded. This results in elevated combustion temperatures and increased NOx emissions. The driver may notice pinging/detonation under load, and the MIL will be illuminated. Performance sy...
The most common cause of P042F (Exhaust Gas Recirculation "A" Control Stuck Closed) is: Carbon buildup sealing the EGR valve shut
Typical repair costs for P042F range from $150 to $550, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Generally safe to drive short distances. Elevated combustion temperatures may cause spark knock/detonation under load, which can damage pistons and head gaskets over time. Avoid heavy towing or sustained high-load driving until repaired.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P042F to identify the root cause.
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Quick Info
Category
Powertrain
System
Exhaust Gas Recirculation (EGR)
Difficulty
Type
Generic (SAE)
Recommended Tools
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