Cruise Control System: Diagnosis Cadillac STS I

Diagnostic Starting Point - Cruise Control

Begin the system diagnosis with the Diagnostic System Check - Vehicle in Vehicle DTC Information. The Diagnostic System Check will provide the following information

1. The identification of the control modules which command the system
2. The ability of the control modules to communicate through the serial data circuit
3. The identification of any stored diagnostic trouble codes (DTCs) and their status

The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and where the procedure is located.

Scan Tool Data List

The scan tool data lists contain all of the cruise control related parameters that are available on the scan tool for the Cruise Control System. The parameters in the list are arranged in alphabetical order. The data list column indicates the location of the parameter within the scan tool menu selections.

Use the scan tool data lists as directed by a diagnostic table or in order to supplement the diagnostic procedures. Begin all of the diagnostic procedures with Diagnostic System Check - Vehicle in Vehicle Control Systems.

Use the scan tool data lists only after the following is determined

1. There is no published DTC procedure nor published symptom procedure for the customer concern.
2. The DTC or symptom procedure indicated by the diagnostic system check does not resolve the customer concern.

The typical data values are obtained from a properly operating vehicle under the conditions specified in the first row of the scan tool data list table. Comparison of the parameter values from the suspect vehicle with the typical data values may reveal the source of the customer concern.

Body and Accessories Data List (3.6L)

Body and Accessories Data List (4.6L)

Scan Tool Data Definitions

The Scan Tool Data Definitions contains a brief description of the Cruise Control System related parameters available on the scan tool.

Scan Tool Data Definitions (Disengage History)

The Cruise Control Scan Tool Definitions - Disengage History is a common list for all of the available cruise control disengagement definitions available on the scan tool. The cruise control system equipped on the vehicle determines which cruise control disengagement parameters are available on the scan tool.

One of the following conditions must be present in order for a disengagement parameter to appear

1. The cruise control system is active and disengagement is requested.
2. The engagement of the cruise control system is requested while a fault is present.

Circuit Description

The cruise control switch is an input to the instrument panel module (IPM). The IPM monitors the cruise control set/coast and resume/accel switch signal circuit in order to detect when the driver has requested a cruise control switch function. The IPM detects a predetermined voltage signal on the cruise control set/coast and resume/accel switch signal circuit indicating which cruise control switch function is being requested by the driver. The engine control module (ECM) receives the requested cruise control switch function via the GMLAN serial data signal circuit.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC B3794 Cruise Control Function Request Circuit

This vehicle has DTCs which include DTC Symptoms. For more information on DTC symptoms, refer to DTC Symptom Description in Vehicle DTC Information.

DTC B3794

Conditions for Running the DTC

1. The cruise control on/off switch is ON.
2. The ignition is ON.

Conditions for Setting the DTC

The IPM will set DTC B3794 when one of the following conditions are present

1. Symptom 01: The IPM detects a high voltage signal on the cruise control set/coast and resume/accel switch signal circuit for greater than 5 seconds.
2. Symptom 08: The IPM detects an invalid voltage signal on the cruise control set/coast and resume/accel switch signal circuit.
3. Symptom 59: The IPM detects a voltage signal on the cruise control set/coast and resume/accel switch signal circuit for greater than 60 seconds.

Action Taken When the DTC Sets

1. The IPM stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The Cruise Control System is disabled.

Conditions for Clearing the DTC

1. The DTC becomes history when the fault is no longer present.
2. A History DTC clears after 50 malfunction free ignition cycles.
3. The IPM receives a clear code command from the scan tool.

Diagnostic Aids

The following are the correct switch resistance value ranges and the correct counts that are displayed in the Cruise parameter in the Body and Accessories / Cruise Control / IPM / Inputs data list, when each switch is pressed individually. If no switch is pressed the resistance value should be infinite.

DTC B3794

1. Ensure that the set/coast or the resume/accel switch is not stuck or sticking in the engaged position.
2. For an intermittent condition, refer to «Testing for Intermittent Conditions and Poor Connections»(ref-197533-S35858719362005101200000) in Wiring Systems.

DTC B3794

The distance sensing cruise control (DSCC) module monitors the ignition 1 voltage circuit in order to determine if the voltage is within the normal operating range.

This diagnostic procedure supports the following DTC

DTC C0800 Device Power 1 Circuit Voltage Below Threshold

This vehicle has DTCs which include DTC Symptoms. For more information on DTC symptoms, refer to DTC Symptom Description in Vehicle DTC Information.

DTC C0800

1. The ignition is in RUN.
2. The vehicle is moving at a speed greater than 40.2 km/h (25 mph).

1. The DSCC module detects that the ignition 1 voltage is less than 9.2 volts.
2. The above condition is present for 7 seconds.

1. Loss of DSCC function
2. Cruise Not Ready indicator illuminates in the driver information center (DIC).

1. The DTC becomes history when the fault is no longer present.
2. A History DTC clears after 100 malfunction free ignition cycles.
3. The DSCC module receives a clear code command from the scan tool.

Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

DTC C0800

The forward looking sensor (FLS) radar is a part of the distance sensing cruise control (DSCC) module but has the exclusive function of detecting, tracking and classifying targets within its specified field of view. The FLS radars ability to detect and react to objects of interest in its detection zone is critical to the proper operation of the adaptive cruise control (ACC) system. When the DSCC module detects that the FLS radar is out of alignment, a DTC C1002 sets.

This diagnostic procedure supports the following DTC

DTC C1002 Distance Sensing Cruise Control Module Range/Performance

The ignition is ON.

1. There is 3.9 degrees of skew or error of the FLS.
2. The vehicle speed is at or greater than 40.2 km/h (25 mph).

1. Loss of ACC function
2. Service Radar Cruise indicator illuminates in the driver information center (DIC).

1. The DTC becomes history when the conditions for setting the DTC are no longer present.
2. The history DTC clears after 100 malfunction free warm-up cycles.
3. The DSCC module receives a clear code command from the scan tool.

1. Align the forward looking sensor (FLS) radar using the FLS alignment tool. An FLS radar out of alignment condition may be as a result of tampering with the DSCC module mounting structures/brackets or the adjuster settings. An out of alignment condition may also be a result of damage to the front section of the ACC equipped vehicle or the DSCC module. Refer to «Distance Sensing Cruise Control Aiming Procedure»(ref-197544-S06528973202005101200000) and «Distance Sensing Cruise Control Module Replacement»(ref-197544-S41050422912005101200000) in order to properly align, adjust, or replace the DSCC module or the DSCC module brackets.
2. Refer to «Cruise Control Description and Operation (Adaptive Cruise Control)»(ref-197544-S18909061442005101200000) or «Cruise Control Description and Operation (Conventional Cruise Control)»(ref-197544-S12181850422005101200000) for the proper operation of the adaptive cruise control (ACC) system.

The stop lamp switch signal circuit is a direct hardwire input to the engine control module (ECM) from the instrument panel module (IPM). The ECM monitors the stop lamp switch signal circuit in order to detect when the brake pedal has been applied. When the brake pedal is pressed, the IPM sends a class 2 serial data message to the ECM indicating that the brake pedal has been applied. The IPM also sends a high voltage signal on the stop lamp switch signal circuit to the ECM. This DTC will set if the class 2 serial data message and the voltage signal on the stop lamp switch signal circuit do not match.

This diagnostic procedure supports the following DTC

DTC P0571 Brake Switch Circuit 1

1. The engine speed is greater than 700 RPM.
2. The Traction Control System or the Antilock Brake System are not active and have not failed.

1. The ECM detects that there is a 8.3 km/h (5.1 mph) or greater decrease in vehicle speed within 1 second.
2. The ECM detects that the class 2 serial data message from the IPM and the voltage signal on the stop lamp switch signal circuit do not match for 10 consecutive times that this diagnostic is run.
3. The above condition is present for greater than 2 seconds.

1. The Cruise Control System is disabled.
2. The ECM stores the DTC information into memory when the diagnostic runs and fails.
3. The malfunction indicator lamp (MIL) will not illuminate.
4. The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records.

1. A last test failed, or the current DTC, clears when the diagnostic runs and does not fail.
2. A history DTC clears after 40 consecutive warm-up cycles, if failures are not reported by this or any other emission related diagnostic.
3. Use a scan tool in order to clear the DTC.

1. In order to avoid a misdiagnosis, inspect for proper operation of the stop lamps. Refer to «Exterior Lighting Systems Description and Operation»(ref-197547-S02329781852005101200000) in Lighting Systems.
2. For an intermittent condition, refer to «Testing for Intermittent Conditions and Poor Connections»(ref-197533-S35858719362005101200000) in Wiring Systems.

DTC P0571

The instrument panel module (IPM) monitors the brake pedal position (BPP) sensor. When the brake pedal is applied, the IPM detects a predetermined voltage signal. The IPM sends a GMLAN serial data message to the transmission control module (TCM) and to the engine control module (ECM) indicating the status of the stop lamps.

This diagnostic procedure supports the following DTC

DTC P0703 Brake Switch Circuit 2

The engine is ON.

1. The TCM or the ECM receives an invalid brake status GMLAN serial data message from the IPM.
2. This diagnostic runs continuously.

1. Autograde braking is inhibited.
2. The Cruise Control System is disabled.
3. The TCM or the ECM stores the DTC information into memory when the diagnostic runs and fails.
4. The malfunction indicator lamp (MIL) will not illuminate.
5. The TCM or the ECM records the operating conditions at the time the diagnostic fails. The TCM or the ECM stores this information in the Failure Records.

1. The DTC becomes history when the fault is no longer present.
2. A history DTC clears after 100 consecutive warm-up cycles, if failures are not reported by this or any other emission related diagnostic.
3. Use the scan tool in order to clear the DTC.

1. Repair any brake system related DTCs before performing this diagnostic table.
2. If an IPM has been replaced, the BPP sensor must be calibrated. Refer to «Brake Pedal Position Sensor Calibration»(ref-197547-S25125530762005101200000) in Lighting System.
3. This DTC may be stored as a history DTC without affecting the operation of the IPM. If stored only as a history DTC and not retrieved as a current DTC, do not replace the IPM.
4. If this DTC is retrieved as both a current and a history DTC, replace the IPM.
5. For an intermittent condition, refer to «Testing for Intermittent Conditions and Poor Connections»(ref-197533-S35858719362005101200000) in Wiring Systems.

Visual/Physical Inspection

1. Inspect for aftermarket devices which can affect the operation of the Cruise Control System. Refer to «Checking Aftermarket Accessories»(ref-197533-S03944243902005101200000) in Wiring Systems.
2. Inspect the accessible system components or the visible system components for obvious damage or for obvious conditions which can cause the symptom.

Symptom List

1. «Cruise Control Gap Up/Down Switch Malfunction»(ref-197544-S29354790622005101200000)
2. «Cruise Control Inoperative/Malfunctioning»(ref-197544-S13046169942005101200000)

The following are the correct resistance value ranges and the correct counts, displayed in the Cruise parameter in the Body and Accessories / Cruise Control / IPM / Inputs data list, when each switch is pressed individually. If no switch is pressed the resistance value should be infinite.

Cruise Control Gap Up/Down Switch Malfunction

For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Cruise Control Gap Up/Down Switch Malfunction

The following are the correct switch resistance value ranges and the correct counts that are displayed in the Cruise parameter in the Body and Accessories / Cruise Control / IPM / Inputs data list, when each switch is pressed individually. If no switch is pressed the resistance value should be infinite.

Cruise Control Inoperative/Malfunctioning

For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Cruise Control Inoperative/Malfunctioning

Scheme 7

Distance Sensing Cruise Control Module Replacement