What it means
The ECM has not yet learned the per-cylinder injection pulse offset for cylinder 7. 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 an individual injection pulse offset for each cylinder to help balance combustion. P2B1C means it has not learned the offset for cylinder 7, so the cylinder 7 correction is unavailable; the condition may follow an ECM reset or replacement of the cylinder 7 injector.
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 P2B1C is current, noting any recent battery disconnect, ECM reset, or cylinder 7 injector work.
- Check for other cylinder-specific or fuel-system codes that could keep the cylinder 7 adaptation from completing.
- Inspect the cylinder 7 injector connector and nearby wiring for damage, corrosion, looseness, or signs of recent work.
- Use a scan tool that supports injector adaptation to check the cylinder 7 learning status and whether the learn procedure is available.
- Perform the manufacturer's cylinder 7 injector learning procedure under its stated conditions, then rescan to confirm the offset is stored.
Common fixes
- Complete the manufacturer's cylinder 7 injection-offset learning procedure.
- Repair a loose, damaged, or corroded cylinder 7 injector connector or wiring.
- If learning will not complete, test the cylinder 7 injector and related fuel system against the manufacturer's specification.
- Replace a confirmed faulty cylinder 7 injector, then perform the required learning procedure.
Can I keep driving?
If the engine only idles slightly rough and has no other warning signs, a short, gentle drive may be possible, but arrange diagnosis soon because cylinder 7 combustion balancing is unavailable and emissions may increase. Stop driving if it 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.