What it means
The ECM has not yet learned the per-cylinder injection pulse offset for cylinder 6. Combustion equalisation between cylinders cannot be applied until adaptation completes.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The ECM learns a separate injection pulse offset for each cylinder to balance combustion. P2B1A means the offset for cylinder 6 has not yet been learned, leaving its individual combustion correction unavailable; an ECM reset or cylinder 6 injector replacement can trigger this condition.
Common causes
Most likely first.
- Adaptation lost after battery disconnect or ECM reset
- Injector replaced without learn procedure
Symptoms
- Check-engine light
- Rough idle
- Slightly reduced engine performance
How to diagnose it
- Read freeze-frame data and confirm P2B1A is current, noting any recent battery disconnect, ECM reset, or cylinder 6 injector replacement.
- Check for other cylinder-specific or fuel-system codes that could prevent the cylinder 6 adaptation from completing.
- Inspect the cylinder 6 injector connector and nearby wiring for looseness, corrosion, damage, or signs of recent work.
- Use a scan tool with injector adaptation support to check the cylinder 6 learning status and whether the required procedure is available.
- Perform the manufacturer's cylinder 6 injector learning procedure under its stated conditions, then rescan to verify the offset has been stored.
Common fixes
- Complete the manufacturer's cylinder 6 injection-offset learning procedure.
- Repair a loose, damaged, or corroded cylinder 6 injector connector or wiring.
- If learning will not complete, test the cylinder 6 injector and related fuel system against the manufacturer's specification.
- Replace a confirmed faulty cylinder 6 injector, then perform the required learning procedure.
Can I keep driving?
If the engine is only slightly rough and there are no other warning signs, a short, gentle drive may be possible, but arrange diagnosis soon because cylinder 6 combustion balancing is unavailable and emissions may increase. Stop if the engine runs severely rough or loses substantial power.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.