Cause
Carbon-coated EGR throttle valve
The diesel intake throttle bound up by the deposits its own position guarantees — it sits exactly where recirculated exhaust soot meets crankcase oil vapour, and the mixture bakes into a paste that stiffens the flap, then sticks it. This is structural, not accidental: the P2413 argument applies, and a valve cleaned without asking why the deposits formed (worn breather, cooked oil, short-trip running) invites the sequel.
The progression is diagnostic in itself: first the position codes report lag (the flap answering slowly), then performance codes (commanded one place, found in another), then the stuck codes — so a lag code is a cleaning appointment offered cheap, and a stuck code is the same appointment after the price went up. Cleaning genuinely works when the flap still moves; a seized spindle or stripped actuator gears need parts.
Typically a moderate job.
Codes this can cause (11)
Codes where this is a likely explanation first, rather than merely a possible one.
- P0487 Exhaust Gas Recirculation Throttle Control Circuit A/Open Likely for this code Moderate
- P0488 Exhaust Gas Recirculation Throttle Control Circuit A Range/Performance Likely for this code Moderate
- P2141 Exhaust Gas Recirculation Throttle Control Circuit A Low Likely for this code High
- P2391 Diesel Intake Air Flow B Control Performance Likely for this code Moderate
- P2394 Diesel Intake Air Flow B Control Stuck Open Likely for this code Moderate
- P2395 Diesel Intake Air Flow B Control Stuck Closed Likely for this code Moderate
- P2397 Diesel Intake Air Flow B Position Sensor Range/Performance Likely for this code Moderate
- P04D9 Closed Loop Exhaust Gas Recirculation Control At Limit — Flow Too Low Moderate
- P2142 Exhaust Gas Recirculation Throttle Control Circuit A High High
- P2AA3 Cold Start Exhaust Gas Recirculation B Flow Insufficient Detected Moderate
- P2AA4 Cold Start Exhaust Gas Recirculation B Flow Excessive Detected Moderate
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