Diagnostic trouble code (DTC) information ECM-4201

Condition 

After start-up, 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 quickly.

Substitute Value 

• None.

Possible Source 

• Air leakage in the exhaust system
• One or more damaged injectors.
• Damaged catalytic converter.

Fault symptom[s] 

• Malfunction indicator lamp (MIL) lit.