Cause
Failed EGR throttle actuator
The motor or vacuum unit that moves the diesel intake throttle, no longer moving it — and the part usually fails second. The flap it drives lives where EGR soot meets oil vapour, the resulting paste stiffens the spindle year by year, and the actuator spends its life working against that growing drag until gears strip or the diaphragm splits. A new actuator fitted to a carbon-bound flap is working against the same drag from day one, which is why the cleaning question precedes the replacement question in every code that lists this cause.
The failure's felt consequence depends on where the flap stops: sprung open costs EGR flow and the smooth shutdown (a switch-off shudder is the classic tell); jammed closed strangles the engine — flat, smoky, possibly stalling — and is the direction that earns urgency.
Typically a moderate job.
Codes this can cause (8)
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
- 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
- P2390 Diesel Intake Air Flow B Control Circuit/Open Moderate
- P2391 Diesel Intake Air Flow B Control Performance Moderate
- P2396 Diesel Intake Air Flow B Position Sensor Circuit Moderate
- P2397 Diesel Intake Air Flow B Position Sensor Range/Performance Moderate
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