P2391

Diesel Intake Air Flow B Control Performance

Severity

⚠️ Medium

Can you drive?

Yes, but get it checked soon

Approx. repair cost

$17–89 (est.)

Symptoms

Reduced engine power
Unstable idling
Increased fuel consumption
Black smoke from the exhaust pipe

Causes

Malfunction of the mass air flow sensor (MAF)
Dirty or stuck air control valve
Open or short circuit in wiring
Air filter dirty
Malfunction of the engine control unit (ECU)

How to Fix

Check the condition of the air filter
Diagnose the mass air flow sensor and its wiring
Check the air flow control valve for dirt and movement.
Scan the ECU for other errors
If necessary, replace faulty components

Related codes