Diagnostic Trouble Code (DTC) Information

Diagnostic trouble code (DTC) information ECM-4201

Condition
The engine control module (ECM) checks the efficiency of the catalytic converter by switching between rich and lean fuel/air mixtures. When the change-over is made, the signal from the rear heated oxygen sensor (HO2S) is checked and the time taken for the probe to switch. The diagnostic trouble code (DTC) is stored if the engine control module (ECM) registers that the rear heated oxygen sensor (HO2S) switches too rapidly. The engine control module (ECM) interprets this as reduced catalytic converter efficiency.
The diagnostic trouble code (DTC) can be diagnosed approximately 15 minutes after the engine is started and if the following requirements are met.
- Speed 50-120 km/h
- Even load, not driving in the city.

Substitute value
- None.

Possible source
- Air leakage in the exhaust system
- Damaged catalytic converter.

Fault symptom[s]
- Malfunction indicator lamp (MIL) lit.