Fuel and air

P01E1 — Cylinder 12 Injection Timing Over-Retarded

Severity: medium Drive with care, to a shop

What P01E1 means

The engine control module compares the actual start of injection in cylinder 12 with its commanded value. If injection consistently happens later than requested, meaning timing is over-retarded, it stores P01E1. It applies to engines with twelve cylinders and usually points to the injector, its circuit, fuel delivery, or engine timing.

Symptoms

  • Check Engine light on
  • Rough idle
  • Reduced power and sluggish acceleration
  • Higher fuel consumption
  • Misfires and engine vibration
  • Possible hard or uneven starting

Possible causes

  1. Faulty or clogged cylinder 12 fuel injector
  2. Open, short or poor connection in the injector wiring or connector
  3. Low fuel pressure or delivery problem
  4. Crankshaft or camshaft position sensor fault affecting injection timing calculation
  5. Mechanical timing offset (stretched chain, jumped timing)
  6. Air leak skewing the mixture
  7. ECM fault or software issue (uncommon)

How to diagnose

  1. Scan all codes and freeze frame data, looking for other cylinder or position sensor codes
  2. Review fuel trims and mixture adaptation values for each bank
  3. Check cylinder balance and misfire counts to confirm cylinder 12
  4. Inspect the cylinder 12 injector connector and harness, then test resistance, power and control signal
  5. Measure fuel pressure and compare with specification
  6. Check crankshaft and camshaft sensor signals
  7. Verify mechanical timing and the condition of the chain or belt
  8. Inspect the intake system for vacuum leaks

Common fixes

  • Replace or clean the cylinder 12 injector
  • Repair wiring and connectors, clean the terminals
  • Fix fuel delivery faults (filter, pump, pressure regulator)
  • Replace a faulty crankshaft or camshaft sensor
  • Correct engine timing or replace the chain and tensioners
  • Reflash or replace the ECM only after other causes are ruled out

Questions and answers

What does P01E1 mean?

The ECM detected that injection in cylinder 12 begins later than commanded. Typical causes are the injector, its wiring, fuel delivery or engine timing.

Can I drive with code P01E1?

Briefly and carefully to a shop, yes, but the engine may misfire and lose power. Prolonged driving worsens combustion and can damage the catalytic converter.

What should I check first?

Start by reading other codes and fuel trims, then inspect the cylinder 12 injector connector and wiring and test fuel pressure. After that, check the position sensors and engine timing.

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.