P02B6: Cylinder 8 - Fuel Trim at Max Limit

What it means

The control module has reached the maximum fuel-trim correction for cylinder 8. This indicates a cylinder-specific mixture correction limit; the code alone does not identify the underlying cause.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The engine control module adjusts fuel for cylinder 8 to keep combustion near its target mixture. This code sets when that cylinder-specific correction reaches its maximum limit, indicating the module can no longer compensate enough; the code alone does not identify the cause.

Common causes

Most likely first.

1. Injector restricted or clogged on cylinder 8
2. Air leak affecting cylinder 8
3. Low fuel pressure or delivery problem
4. Cylinder 8 sensor, wiring, or control fault

Symptoms

• Check-engine light
• Rough idle or engine vibration
• Misfire or hesitation
• Reduced engine power

How to diagnose it

1. Record freeze-frame data and compare cylinder 8 fuel-trim or mixture data with other cylinders to see under what conditions correction reaches its maximum.
2. Check cylinder 8 misfire and contribution data to confirm whether the problem is isolated to that cylinder.
3. Inspect the cylinder 8 injector connector, wiring, and nearby intake or vacuum connections for damage or an air leak affecting that cylinder.
4. Check fuel quality and measure fuel pressure or delivery under the conditions shown in the freeze-frame, comparing results with the manufacturer's specification.
5. Use an approved injector balance or flow test to check whether cylinder 8 is receiving less fuel than the other cylinders.
6. If fuel delivery and air leaks check out, test relevant cylinder 8 sensors, wiring, and control circuits against the manufacturer's specification.

Common fixes

• Repair a leak at an intake connection or vacuum hose affecting cylinder 8.
• Repair damaged cylinder 8 injector wiring or connector contacts.
• Correct a restricted fuel supply or fuel pressure problem.
• Clean or replace the cylinder 8 injector if testing confirms restricted delivery.

Can I keep driving?

If the engine runs smoothly, a short, gentle trip may be possible, but avoid hard acceleration because cylinder 8 may be running too lean. Stop driving if it misfires badly or the check-engine light flashes, since continued misfire can damage the catalytic converter.