Diagnostic trouble code (DTC) information ECM-233C

Condition 

Fig 1: Identifying Rear Heated Oxygen Sensor

Courtesy of VOLVO CARS OF NORTH AMERICA.

The engine control module (ECM) controls preheating by pulsing the current to the positive temperature coefficient (PTC) element in the heated oxygen sensor (HO2S). Pulse lengths are dependent on the temperature of the heated oxygen sensor (H02S).

The diagnostic trouble code (DTC) is stored if the engine control module (ECM) registers that the signal is higher than a certain value when preheating is active.

Substitute Value 

• The fuel trim is shut off.

Possible Source 

• Short-circuit to supply voltage in the signal cable
• Damaged heated oxygen sensor (HO2S).

Fault symptom[s] 

• Malfunction indicator lamp (MIL) lit.