Heated Oxygen Sensor (Ho2S) Diagnostic

The front heated oxygen sensor (HO2S) is a linear type and functions with current control. Therefore it is possible to measure the signals from the heated oxygen sensor (HO2S) using a multimeter. The rear heated oxygen sensor (HO2S) is a binary type as with earlier heated oxygen sensors (HO2S). The center heated oxygen sensor (HO2S) (certain markets only) is also binary. It works in the same way as previous heated oxygen sensors (HO2S).

The engine control module (ECM) checks the heated oxygen sensors (HO2S) when the conditions for the diagnostic have been met.

The following faults can be registered by the control module:

• Electrical faults in circuits  for the actual heated oxygen sensors (HO2S) and in their preheating
• Adaptation.  The control module checks that the long-term fuel trim is not higher or lower than the pre-defined values
• Heated oxygen sensor (HO2S) dynamics.  The control module checks that the switch time between rich and lean mixture is not too long.