Diagnostic trouble code (DTC) information
Condition
Diagnostic trouble code (DTC) ECM-3503 is stored at start up if the engine control module (ECM) detects misfiring during the first 1000 revs after engine start up.
Diagnostic trouble code (DTC) ECM-3503 emission effect or ECM-3503 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 revs 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
- Leakage diagnosis shut off
- Rear heated oxygen sensor control shut off
- Fuel trim switched off.
Possible Source
- Low fuel level
- Repeated cold starting where the engine coolant temperature (ECT) has reached normal operating temperature between starts
- Water in the spark plug wells
- Defective spark plug
- Contaminated or incorrect fuel
- Poor fuel quality (summer fuel in winter).
- Blocked / leaking injector
- Air leakage
- Blocked crankcase ventilation.
- Damaged VVT-unit.
- 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.