What does it mean?
On this type of engine the module does not assume that an injector fires exactly when it is told to; it verifies the result. By analysing how the crankshaft accelerates during each firing event, and where the hardware allows by reading needle-lift or combustion-pressure feedback, it works out when combustion in cylinder 6 really started. Storing this code means that start of combustion was consistently later than the commanded point, beyond the retard limit written into the calibration. A late burn loses expansion work, drops the torque contribution of cylinder 6 and leaves more unburned fuel in the exhaust. The monitor only runs with the engine warm and the load steady, so the code reflects a repeatable deviation rather than one odd event.
Symptoms
- MIL (check engine lamp) on and, in many cases, a stored misfire code for the same cylinder.
- The engine idles roughly and the vibration can be felt through the pedals and the steering wheel.
- Sluggish throttle response and a flat spot when accelerating.
- Difficult cold starting with extended cranking and a puff of smoke when the engine catches.
- Fuel consumption creeps up and the exhaust smells strongly of unburned fuel.
- Some vehicles restrict engine output and enter limp mode once the fault has repeated.
Likely causes
- An injector on cylinder 6 that has become sluggish through wear, carbon build-up or internal deposits.
- Calibration or trim codes never written after a replacement, or copied from the wrong injector.
- Insufficient high-pressure rail pressure while the monitor is running, so the nozzle starts to deliver later than planned.
- Voltage drop in the injector supply or return path: a loose connector pin, a corroded splice or a poor ground.
- Contaminated fuel, water in the fuel, or air drawn into the high-pressure circuit through a leaking union.
- Timing drive wear such as chain stretch, a worn tensioner or an incorrectly installed belt, which offsets the crankshaft reference.
- A weakening injector driver stage inside the control module.
How to fix it
- Note the freeze frame conditions, then reproduce them on a road test while logging the relevant data.
- Log the injector correction values for every cylinder and see how far cylinder 6 sits from the group.
- Verify that actual rail pressure follows the commanded value at idle, part load and full load.
- Test the injector circuit for cylinder 6: measure winding resistance, check for a clean ground and confirm the drive signal with a scope or current clamp where available.
- Perform a return-flow test with the engine running to identify a nozzle passing more fuel than the others.
- Inspect the timing drive and verify camshaft-to-crankshaft correlation if the deviation shows on more than one cylinder.
- Once the injector is replaced or reconditioned, program its calibration code, carry out the injector learning procedure and confirm the corrected value on a follow-up road test.