2010 Cadillac Truck SRX AWD V6-2.8L Turbo Page 1106

2010 Cadillac Truck SRX AWD V6-2.8L Turbo Page 1106

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

* DTC P0117 or P0118 is not set.

* The HO2S 2 is at operating temperature for greater than 90 seconds.

* The engine is operating for greater than 5 seconds.

* The ignition voltage is greater than 10 volts.

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

the ignition was turned OFF last ignition cycle.

* DTCs P0137 runs continuously once the above conditions are met.

P0138 and P0140

* The HO2S 2 is at operating temperature for greater than 30 seconds.

* The engine is operating for greater than 1 second.

* The ignition voltage is greater than 10 volts.

* DTCs P0138 runs continuously once the above conditions are met for greater than 5 seconds.

* DTCs P0140 runs continuously once the above conditions are met for greater than 60 seconds.

Conditions for Setting the DTC

P0137

The ECM detects that a secondary HO2S signal voltage is less than 60 mV for greater than 1 seconds of for a cumulative of 10 seconds.

P0138

The ECM detects that the HO2S signal voltage is greater than 1,150 mV for greater than 1 seconds or for a cumulative of 10 seconds.

P0140

* The ECM detects that the HO2S 2 signal voltage is between 401-519 mV, when the calculated exhaust temperature is less than 800掳C (1,472

掳F).

* The ECM detects that the HO2S 2 signal voltage is between 401-548 mV, when the calculated exhaust temperature is greater than 800掳C

(1,472掳F).

* The ECM detects that the measured internal resistance of the HO2S is greater than 40,000 ohm, when the calculated exhaust temperature is

greater than 450掳C (802掳F).

* The ECM detects any one of the above conditions for greater than 1 second or for a cumulative of 10 seconds.

Action Taken when the DTC Sets

DTCs P0137, P0138, and P0140 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0137, P0138, and P0140 are Type B DTCs.