2010 Cadillac CTS Sedan AWD V6-3.6L Page 1104

2010 Cadillac CTS Sedan AWD V6-3.6L Page 1104

DTC P0138

- HO2S Circuit High Voltage Bank 1 Sensor 2

DTC P0140

- HO2S Circuit Insufficient Activity Bank 1 Sensor 2

DTC P0157

- HO2S Circuit Low Voltage Bank 2 Sensor 2

DTC P0158

- HO2S Circuit High Voltage Bank 2 Sensor 2

DTC P0160

- HO2S Circuit Insufficient Activity Bank 2 Sensor 2

Diagnostic Fault Information

Typical Scan Tool Data

Circuit Description

The heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding

air with the oxygen content of the exhaust stream. When the engine is started, the control module operates in an Open Loop mode, ignoring the

HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference, or bias voltage of about 450

mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above

and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control

module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a

rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.

The heating elements inside each HO2S heat the sensor to bring the sensor up to operating conditions faster. This allows the system to enter Closed

Loop earlier and the control module to calculate the air-to-fuel ratio sooner.

Conditions for Running the DTCs

P0137 and P0157

* DTC P0036, P0037, P0038, P0056, P0057, P0058, P0116, P0117, P0118, P0119, or P0128 is not set.

* The engine speed is greater than 240 RPM.

* The ignition voltage is greater than 10 volts.

* The engine coolant temperature is colder than 40掳C (104掳F) at start-up and the engine coolant temperature was warmer than 60掳C (140掳F)

when the ignition was turned OFF last ignition cycle.

* The calculated exhaust temperature at the HO2S 2 is warmer than 700掳C (1,292掳F) and the HO2S 2 is warmed up for greater than 90

seconds.

* The calculated exhaust temperature is colder than 800掳C (1472掳F) 5 seconds after engine start.

* DTCs P0137 and P0157 run continuously once the above conditions are met.

P0138, P0140, P0158, and P0160

* The engine speed is greater than 240 RPM.

* The ignition voltage is greater than 10 volts.

* The HO2S 2 heater duty cycle is stable and the HO2S 2 is warmed up for greater than 90 seconds.