P2B08: Cold Start Cylinder 1 Injection Pulse Performance

What it means

During cold start, the ECM detects that the injection pulse on cylinder 1 does not produce the expected combustion result. Cold-start specific pulse calibration deviates from learned values.

At a glance

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

How it works

During a cold start, the ECM evaluates how cylinder 1 responds to its injector command using cold-start calibration and learned behavior. P2B08 sets when cylinder 1's cold injection performance falls outside that expected response, which can result from temperature-sensitive injector behavior or poor fuel atomization.

Common causes

Most likely first.

1. Injector behaviour drifts at low temperature
2. Poor fuel atomization at cold start

Symptoms

• Check-engine light may be on
• Rough idle after a cold start
• Hesitation or reduced power while cold

How to diagnose it

1. After the vehicle has sat cold, record freeze-frame data at startup and compare cylinder 1 misfire or contribution readings with the other cylinders.
2. Note whether the rough idle or hesitation occurs only when cold and whether it clears as the engine warms.
3. Inspect cylinder 1's injector connector and wiring for damage, corrosion, or a loose fit.
4. Use scan-tool cold-start data to compare cylinder 1's injector command and combustion contribution with the remaining cylinders.
5. If cylinder 1 remains abnormal during cold operation, have its injector spray and flow assessed against the manufacturer's specification.

Common fixes

• Use the specified fuel and monitor whether cold-start symptoms persist after suspect fuel is no longer in the tank.
• Repair a poor connection or damaged wiring at the cylinder 1 injector.
• Clean or service the cylinder 1 injector if poor atomization from deposits is confirmed and it is serviceable.
• Replace the cylinder 1 injector if cold-condition testing shows performance outside the manufacturer's specification.

Can I keep driving?

If the roughness is mild and clears quickly with a steady warning light, avoid hard acceleration while cold and arrange diagnosis soon because repeated poor cold combustion increases emissions. Stop if the warning light flashes, the engine shakes severely, or it stalls in traffic.