Diagnostic Trouble Code (DTC) Information

Diagnostic trouble code (DTC) information ECM-3503

Condition
The diagnostic trouble code (DTC) for start up problems is stored at start up if the engine control module (ECM) detects a certain number of misfires during the first 1000 engine revolutions.
The diagnostic trouble code (DTC) for emission effect or three-way catalytic converter (TWC) damage is stored (depending on the seriousness of the misfire) if the engine control module (ECM) detects misfiring after the first 1000 engine revolutions after engine start up.
The diagnostic trouble code (DTC) is always stored together with a diagnostic trouble code (DTC) which indicates the cylinder which is misfiring (ECM-35X3).

Substitute value
- Three-way catalytic converter (TWC) diagnosis shut off
- Leak diagnostic shut off
- Rear heated oxygen sensor control shut off
- Fuel trim switched off.

Possible source
- Low fuel level
- The engine does not reach normal operating temperature between several cold starts
- Water in the spark plug wells
- Damaged spark plug
- Contaminated or incorrect fuel
- Poor fuel quality (summer fuel in winter).
- Air leakage
- Blocked crankcase ventilation.
- Damaged VVT-unit.
- Blocked / leaking injector
- Faulty fuel pressure
- Uneven compression

Fault symptom[s]
- The malfunction indicator lamp (MIL) flashes
- The engine misfires
- The engine is difficult to start
- Deterioration in performance
- Uneven idle
- The engine is not firing on all cylinders.