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.

The cruise control switch is an input to the body control module (BCM). The BCM monitors the cruise control set/coast and resume/accelerate switch signal circuit in order to detect when the driver has requested to perform a cruise control function. The BCM detects a specific voltage signal on the cruise control set/coast and resume/accelerate switch signal circuit when a switch is applied.

For an intermittent, refer to Testing for Intermittent Conditions and Poor Connections.

DTC B3812 : Content Theft System Sensor Ground Circuit

The Content Theft Deterrent function provides the theft deterrent by sounding the horn and flashing the headlamps and the park lamps when there is an unauthorized vehicle entry or there is tampering detected.

This DTC sets if the BCM detects an open and a short to voltage or ground in the intrusion ground circuit.

The current DTC will become history when the request for the output is removed or when the condition for setting the fault is corrected.

DTC B3873 : Front Washer Relay Circuit

The windshield washer function is controlled by the body control module (BCM). When the washer switch is pressed, ground is applied through the switch contacts and the signal circuit to the BCM indicating the wash request. The BCM then applies ground through the control circuit to the coil side of the Front Washer Pump Relay energizing the relay. With the relay energized, battery voltage from the Ef2 and the F3 fuse is applied through the switch contacts of the relay and the control circuit to the windshield washer fluid pump.

This DTC can set only when the output is actively being requested by the BCM.

This DTC sets if the BCM detects a short to battery voltage in the wiper high speed relay control circuit.

The BCM will not activate the output.

DTC B3875 : Wiper High Speed Relay Circuit

The body control module (BCM) monitors the wiper high speed relay control circuit only when wiper high speed mode is active. When the wiper high speed mode is requested, the BCM responds by applying a ground through the wiper high speed relay control circuit to the coil side of the relay, energizing the Wiper Speed Relay.

This DTC can set only when the output is actively being requested by the BCM.

This DTC sets if the BCM detects a short to battery voltage on the wiper high speed relay control circuit.

The BCM will not activate the output.

This diagnostic procedure supports the following DTC:

DTC B3922 Front Wiper Function Select Circuit

The body control module (BCM) monitors the windshield wiper switch low signal circuit. When the wiper switch is place in the low position, battery voltage is applied through the switch contacts, a series of resistors, and the wiper switch low signal circuit to the BCM. The BCM then applies battery positive voltage to the wiper relay control circuit which energizes the wiper relay. This applies battery voltage from the WPR Fuse through the switch side of the relay to the windshield wiper motor.

The BCM detects a short to ground or a short to battery voltage on the windshield wiper switch low signal circuit.

Perform a visual inspection for loose or poor connections at all related components.

DTC B3933 : Air Conditioning (A/C) Evaporator Temperature Sensor Circuit Voltage Above Thershold

The HVAC control module monitors the evaporator temperature via the evaporator temperature sensor. When the air is cold, the sensor resistance and signal voltage are high. When the air is warm, the sensor resistance and signal voltage are low.

The HVAC control module detects the evaporator temperature sensor signal circuit is less than 0.09 volt (5 counts) or greater than 4.90 volts (250 counts).

The numbers below refer to the step numbers on the diagnostic table.

DTC P0826 : Up And Down Shift Switch Circuit

The BCM shall monitor the TUTD(Tap Up/Tap Down) switches located in the passenger compartment that the driver can activate in order to manually control the shifting of an automatic transmission. Two types of TUTD systems shall be supported:

Drivers Shift Control: When this feature is activated the transmission freezes in the current gear and the TUTD switches are used to commanded it upshift or downshift from there.

Electronic Range Select: When this feature is active the TUTD switches are used to control the maximum gear that the transmission will operate in but it automatically shifts into gears lower than the established limit as conditions warrant.

The BCM shall monitor the TUTD ON/OFF switch to activate / deactivate the Driver Shift Control feature or Electronic Range Select feature, selectable via calibration. The status of these features shall be communicated to the Powertrain system via high speed LAN.

The BCM shall monitor the TUTD switches and communicate their status to the Powertrain system via high speed LAN.

The BCM shall implement diagnostic algorithms for the TUTD switch input to detect open circuits, shorts to battery or ground, and stuck switches. If the BCM detects any failure with the TUTD switch mechanism it shall automatically deactivate the Driver Shift Control and Electronic Range Select feature.

BCM detects open circuits, shorts to battery or ground, and stuck switches.

Drive shift control is inhibited.

A current DTC will clear when the malfunction is no longer present.

DTC U0073 : Control Module Communication Bus Off

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

The high speed GMLAN serial data circuits are high speed serial data buses used to communicate information between the control modules. Typical data transmission speeds must be high enough to ensure that a required real-time response is maintained. The high speed GMLAN serial data circuits also connect directly to the data link connector (DLC).

The module setting the DTC has attempted to establish communications on the GMLAN circuits more than 3 times.

DTC U0100 : Lost Communication With Engine/Powertrain Control Module (ECM/PCM)

DTC U0101 : Lost Communication With Transmission Control Module (TCM)

DTC U0155 : Lost Communication With Instrument Panel Cluster (IPC) Control Module

DTC U0164 : Lost Communication With Body Control Module (BCM)

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Modules connected to the high and low speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.

The body control module (BCM) activates the serial data communication enable and the accessory wakeup serial data circuits by applying voltage when the ignition key is in ACC, ON or START. The serial data communication enable circuit wakes up the electronic brake control module (EBCM) for bus communication and the accessory wakeup serial data circuit wakes up the engine control module (ECM) and transmission control module (TCM).

A supervised periodic message that includes the transmitter module availability has not been received.

The module(s) is never signaled, therefore the specific subsystem(s) will not function.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

DTC U1814 : Powertrain High Speed Communication Enable Circuit

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

The accessory wakeup serial data circuit is a positive voltage signal to wake up the engine control module (ECM) and the transmission control module (TCM). The signal is activated in 2 ways; any time the ignition switch is in the ACC or RUN position, or anytime the body control module (BCM) determines that communication is needed from the powertrain. When the ignition switch is in the ACC or RUN position, the accessory voltage circuit input to the BCM is internally connected to the accessory wakeup serial data circuit output, and voltage is supplied to the modules. The BCM also supplies voltage to the accessory wakeup serial data circuit when it determines that communication is necessary with the powertrain and the ignition is not in the ACC or RUN position such as during remote start.

The BCM senses a short to ground on the accessory wakeup serial data circuit.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Refer to Control Module References for module replacement and programming.

DTC U2099 :High Speed Communication Enable Circuit

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

The body control module (BCM) activates the serial data communication enable circuit, when the ignition key is in ACC, ON or START. The serial data communication enable circuit wakes up the electronic brake control module (EBCM) for buss communication.

The BCM senses a short to ground on the serial data communication enable circuit.

Use the scan tool to observe the HS Comm. Cmd. parameter in the BCM data list/outputs with the driver door open and key out of the ignition, and with the ignition in the RUN position. The reading should match the normal range of the typical scan tool data above.

If all parameters are correct and the DTC is current, replace the BCM.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Refer to Control Module References for module replacement and programming.