2010 Cadillac CTS Sedan AWD V6-3.6L Page 1091

2010 Cadillac CTS Sedan AWD V6-3.6L Page 1091

Circuit/System Verification

1. DTC P150C is an informational DTC. Diagnose all other Engine Control DTCs prior to DTC P150C. Refer to Diagnostic Trouble Code

(DTC) List - Vehicle (See: Diagnostic Trouble Code Descriptions/Diagnostic Trouble Code (DTC) List - Vehicle).

2. If there are no other Engine Controls DTCs, diagnosis is accomplished by looking for an intermittent CAN circuit fault. Refer to Scan Tool

Does Not Communicate with High Speed GMLAN Device (See: Powertrain Management/Computers and Control Systems/Information

Bus/Testing and Inspection/Symptom Related Diagnostic Procedures/Scan Tool Does Not Communicate with High Speed GMLAN Device).

P0151

DTC P0131 or P0151 (with LLT)

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 P0131

- HO2S Circuit Low Voltage Bank 1 Sensor 1

DTC P0151

- HO2S Circuit Low Voltage Bank 2 Sensor 1

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 DTC