P02AF - Cylinder 4 Fuel Trim at Max Limit
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System
Powertrain (Engine & Gearbox)
Related Fault Codes
Technical Description
P02AF indicates that the Engine Control Module (ECM) has reached its adaptive learning limit for fuel compensation on cylinder 4. The system is attempting to compensate for an extremely lean condition by increasing injector pulse width (duty cycle), but has reached the maximum allowable correction factor. This is typically monitored through crankshaft speed fluctuations (per-cylinder contribution) or individual cylinder air-fuel ratio monitoring via the O2 sensor. When the trim exceeds a specific threshold (typically >25%), the code is stored.
Possible Causes
Clogged or faulty fuel injector on cylinder 4
Intake manifold vacuum leak near cylinder 4
Faulty spark plug or ignition coil causing incomplete combustion
Mechanical engine problem (low compression) or wiring harness issues to the injector
Symptoms
Recommended Solution
Workflow
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
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