2010 Cadillac Truck SRX AWD V6-2.8L Turbo Page 1111

2010 Cadillac Truck SRX AWD V6-2.8L Turbo Page 1111

* Control Module References (See: Testing and Inspection/Programming and Relearning) for engine control module replacement, setup, and

programming

P0140

DTC P0137, P0138, or P0140 (Without LF1)

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System

Check - Vehicle) prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an

overview of the diagnostic approach.

* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure

Instructions) provides an overview of each diagnostic category.

DTC Descriptors

DTC P0137

- HO2S Circuit Low Voltage Sensor 2

DTC P0138

- HO2S Circuit High Voltage Sensor 2

DTC P0140

- HO2S Circuit Insufficient Activity 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

* 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