Fuel and air

P01CB — Cylinder 1 Injection Timing Over-Retarded

Severity: medium Drive with care, to a shop

What P01CB means

The engine control module compares the actual start of fuel injection in cylinder 1 with the expected timing. P01CB sets when injection happens later than the allowed limit. This is most common on systems where injection timing is tightly controlled, such as diesel and direct injection. Late injection makes combustion poor and the cylinder runs unevenly.

Symptoms

  • Check Engine light on
  • Rough idle or uneven running
  • Reduced engine power
  • Exhaust smoke at start-up
  • Increased fuel consumption
  • Possible misfire on cylinder 1

Possible causes

  1. Faulty or sticking cylinder 1 fuel injector
  2. Damaged, corroded or loose injector wiring or connector
  3. Crankshaft or camshaft position sensor fault feeding bad data to the ECU
  4. Valve timing deviation or another engine mechanical problem
  5. Low or unstable fuel pressure
  6. Intake air leak distorting the mixture

How to diagnose

  1. Scan all codes and freeze frame data, looking for related injection, crankshaft or camshaft sensor codes
  2. Review fuel trims and mixture adaptation values
  3. Compare cylinder balance or contribution to isolate cylinder 1
  4. Inspect the injector 1 wiring and connector, and test circuit resistance, power and ground
  5. Measure fuel pressure and compare it to specification
  6. Check for intake and exhaust leaks
  7. Verify valve and injection timing if everything else checks out
  8. Test the injector, or swap it with a neighbor and see whether the fault follows it

Common fixes

  • Replace or service the cylinder 1 injector
  • Repair or replace damaged wiring and connectors
  • Replace a faulty crankshaft or camshaft position sensor
  • Fix the cause of low fuel pressure (pump, filter, regulator)
  • Repair intake air leaks
  • Correct valve timing or other mechanical engine faults

Questions and answers

What does P01CB mean?

The ECU detected that fuel injection in cylinder 1 starts too late compared with the expected timing. The cause may be the injector, wiring, sensors or an engine mechanical issue.

Can I drive with a P01CB code?

Only briefly and carefully, to get to a repair shop. The engine may run rough and lose power, and prolonged driving increases fuel use and strain on the exhaust system.

Where should I start diagnosing P01CB?

Start with the injector 1 wiring and connector, then check cylinder balance, fuel trims and fuel pressure. That helps separate an injector problem from a fuel supply or mechanical one.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.