Fuel and air

P01DB — Cylinder 9 Injection Timing Over-Retarded

Severity: medium Drive with care, to a shop

What P01DB means

P01DB means the actual start of fuel injection in cylinder 9 is occurring much later than the timing the engine control module commanded. The ECM compares the target timing with crankshaft and camshaft position signals and the injector's response. This code appears only on engines with at least nine cylinders, such as V10 and V12 gasoline engines or some large diesels.

Symptoms

  • Check engine light on
  • Rough idle or misfire on cylinder 9
  • Reduced engine power
  • Poor fuel economy
  • Hesitation or surging under acceleration
  • Harsh or noisy running (on diesels)

Possible causes

  1. Faulty or clogged cylinder 9 fuel injector
  2. Wiring or connector fault in the injector circuit
  3. Low or unstable fuel pressure
  4. Faulty crankshaft or camshaft position sensor
  5. Air leak affecting the mixture
  6. Internal ECM fault (uncommon)

How to diagnose

  1. Scan all codes and freeze-frame data, looking for other injector or position sensor codes
  2. Review fuel trims and mixture adaptation values
  3. Compare cylinder balance or contribution for each cylinder
  4. Inspect the cylinder 9 injector connector and harness, checking power, ground and the control signal
  5. Measure injector resistance and scope the drive pulse
  6. Test fuel pressure and its stability
  7. Check crankshaft and camshaft sensor signals
  8. Look for intake and exhaust leaks

Common fixes

  • Clean or replace the cylinder 9 injector
  • Repair the injector wiring or connector
  • Replace a faulty crankshaft or camshaft position sensor
  • Fix the cause of low fuel pressure (pump, filter, regulator)
  • Reflash or replace the ECM only if everything else checks out

Questions and answers

Can I drive with a P01DB code?

Briefly and carefully, for example to a shop, if the engine runs smoothly. If it misfires, loses a lot of power or the check engine light flashes, shut it off.

What most often causes P01DB?

Most often it is the cylinder 9 injector or its wiring. Fuel pressure problems and position sensors are less common, so the injector circuit is usually checked first.

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.