Door System, Mirror System & Window System: Overview Chevrolet TrailBlazer I

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

1. 2. Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
2. 5. The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.

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Scheme 50

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

1. 2. This step determines if the heated/memory seat switch illumination circuit is the cause for DTC B1017 setting.
2. 3. This step determines if the mirror heating element supply voltage circuit is the cause for DTC B1017 setting.
3. 4. This step eliminates the possibility that the heated/memory seat switch is internally shorted to ground.

Scheme 51

The number(s) below refer to the step number(s) on the diagnostic table.

1. 2. Listen for an audible click when the rear door lock relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 3. Tests for voltage at the coil side of the rear door lock relay. The LOCKS fuse supplies power to the coil side of the rear door lock relay.
3. 4. Verifies that the body control module is providing ground to the rear door lock relay.
4. 5. Tests if ground is constantly being applied to the rear door lock relay.

Scheme 52

The number(s) below refer to the step number(s) on the diagnostic table.

1. 2. Listen for an audible click when the rear door unlock relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 3. Tests for voltage at the coil side of the rear door unlock relay. The LOCKS fuse supplies power to the coil side of the rear door unlock relay.
3. 4. Verifies that the body control module is providing ground to the rear door unlock relay.
4. 5. Tests if ground is constantly being applied to the rear door unlock relay.

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Scheme 54

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

1. 2. Listen for an audible click when the left rear power window relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 3. Tests for voltage at the coil side of the left rear power window up relay.
3. 4. Verifies that the BCM is providing ground to the left rear power window up relay.
4. 5. Tests if ground is constantly being applied to the left rear power window up relay.

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Scheme 56

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

1. 2. Listen for an audible click when the left rear power window relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 3. Tests for voltage at the coil side of the left rear power window down relay.
3. 4. Verifies that the BCM is providing ground to the left rear power window down relay.
4. 5. Tests if ground is constantly being applied to the left rear power window down relay.

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

1. 2. Listen for an audible click when the right rear power window relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 3. Tests for voltage at the coil side of the right rear power window up relay.
3. 4. Verifies that the BCM is providing ground to the right rear power window up relay.
4. 5. Tests if ground is constantly being applied to the right rear power window up relay.

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Scheme 60

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

1. 2. Listen for an audible click when the right rear power window relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 3. Tests for voltage at the coil side of the right rear power window down relay.
3. 4. Verifies that the BCM is providing ground to the right rear power window down relay.
4. 5. Tests if ground is constantly being applied to the right rear power window down relay.

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Power Window Motor Operation

A permanent magnet motor operates each of the power side windows. Each motor raises or lowers the glass when the motor receives voltage. The direction the motor turns depends on the polarity of the supply voltage. The power window switches control the polarity of the supply voltage. A built-in circuit breaker protects each motor. The circuit breaker opens when the switch is depressed for a extended period of time under the following conditions

1. The window has an obstruction.
2. The window is fully open or fully closed.

The circuit breaker will reset automatically as the circuit breaker cools.

Driver Power Window Operation

The switch for the driver power window has three positions UP, Down and Express Down and its position is a direct input into the DDM. Upon receiving a request for power window operation (switch activation), the DDM supplies voltage to the power window motor left front up or down circuit and grounds the opposite and the power window motor runs to move the window up or down.

Front Passenger Power Window Operation

The switch for the front passenger power window has two positions UP and Down, and its position is a direct input into the PDM. Upon receiving a request for power window operation (switch activation), the PDM supplies voltage to the power window motor right front up or down circuit and grounds the opposite and the power window motor runs to drive the window up or down.

The front passenger power window can also be controlled from the power window master switch. The power window master switch for the front passenger power window has three positions UP, Down and Express Down and its position is a direct input into the DDM. Upon receiving a request for front passenger power window operation (switch activation), the DDM transmits a Class 2 message indicating the changed switch position. When the PDM receives this message, the PDM supplies voltage to the power window motor right front up or down circuit and grounds the opposite and the power window motor runs to move the window up or down.

Rear Passenger Power Window Operation

The passenger power window switches incorporate window up and down relays. The supply side of all the window up and down relays receive voltage through the battery voltage supply circuit and the LT DOOR or RT DOOR circuit breakers respectively. The normally closed contacts of each relay is connected to ground. The load side of each of the relays are connected to either side of the power window motor through the power window up and down circuits.

The relay coil feed circuits are connected to the BCM through the power window lockout control circuit and the relay control circuits are connected to the power window switches and to the BCM.

If a rear power window switch is placed in the down position, the down relay would energize and allow battery voltage to the power window motor through the power window motor down circuit. Since the opposite side of the motor is connected to the normally closed contacts of the up relay to ground through the power window motor up circuit, the window moves down. If a rear power window switch is placed in the up position, the up relay would energize and allow battery voltage to the power window motor through the power window motor up circuit. Since the opposite side of the motor is connected to the normally closed contacts of the down relay to ground through the power window motor down circuit, the window moves up.

The rear passenger power windows can also be controlled from the power window master switch. The power window master switches for the rear passenger power windows have two positions UP and Down and its position is a direct input into the DDM. Upon receiving a request for rear passenger power window operation (switch activation), the DDM transmits a Class 2 message indicating the changed switch position. When the BCM receives this message, the BCM can control the rear window up and down relays.

Express Down Operation

The express down function controls both the driver and front passenger power windows but only from the driver door power window master switch. When either the driver or front passenger window switch is momentarily depressed to the express down position, it is a direct input into the DDM. If the request was for the driver power window, the DDM supplies voltage to the power window down circuit continuously until the power window reaches the bottom of its travel. At this point, the DDM senses an over current situation on the power window down circuit and interrupts the voltage supply. If the request was for the front passenger power window, the DDM transmits a Class 2 message indicating an express down function was requested. When the PDM receives this message, the PDM supplies voltage to the power window down circuit continuously until the power window reaches the bottom of its travel. At this point, the PDM senses an over current situation on the power window down circuit and interrupts the voltage supply.

Power Window Lockout Operation

The DDM contains a window lockout switch that is responsible for the disabling of all the passenger windows from the individual passenger window switches. When the window lockout switch is activated, the DDM transmits a Class 2 message indicating that a window lockout request has been received. When the PDM receives this message, it will disable the power window motor up and down circuits. When the BCM receives this message, it will interrupt the up and down relay coil feed voltage for both rear doors. Once activated, the lockout feature will remain in effect until the ignition switch is cycled or the DDM receives another power window lockout switch activation.

Power Door Lock Operation

The power door lock switches are integral components of the DDM and PDM. The switches are two position normally open rocker switches. When placed in either the lock or unlock positions, the switches provide a direct input to the DDM or PDM. The DDM or PDM monitors these inputs and sends a Class 2 message indicating a change in the switch's respective position. Modules which activate the power door lock motors receive the Class 2 message and activate the motor in the appropriate direction to lock or unlock the vehicle's doors and liftgate. The modules which activate the power lock motors are

1. DDM (driver door lock actuator).
2. PDM (passenger front door lock actuator).
3. BCM (both rear door lock actuators).
4. LGM (liftgate door lock actuator).

The DDM, PDM and LGM are directly connected to the respective door lock actuator through the door lock motor lock and unlock circuits. Once a door lock or unlock request has been received, the module will supply battery voltage to one side of the actuator and ground the other causing the doors to lock or unlock.

The rear passengers doors differ slightly in that they use lock and unlock relays. The relays supply and coil sides receive a constant voltage through the battery voltage supply circuit. The normally closed contacts are connected to ground and the control side is connected to the BCM. Once a door lock or unlock request has been received by the BCM, the BCM will ground the control side of the appropriate relay. This energizes the relay and allows voltage to be applied to either the door lock motor lock or unlock circuits. Since the other side of the door lock actuator is connected to the normally closed contacts of the opposing relay to ground, the doors lock or unlock.

Power Mirror System Operation

The power mirror switch receives power from the DDM through the battery supply voltage circuit and the DDM fuse. The left and right mirror positions of the select switch and four positions of the direction switch, when active, will provide a battery voltage signal to the DDM through their respective signal circuits. If the selector switch is placed in the L position and the up switch is depressed, a battery voltage signal will be supplied to the DDM through the driver mirror select switch signal and the mirror motor up switch signal circuits. The DDM upon receipt of these signals will provide battery voltage to the mirror motor left/up control circuit and ground to the mirror motor down control circuit and the mirror will move up. The remainder of the driver mirror functions operate in the same manner as described above except the DDM will supply battery voltage and ground to the appropriate control circuits for the direction selected. If the passenger mirror is selected and a direction switch is activated, the DDM sends a class 2 message to the PDM indicating that the passenger mirror was selected and the direction to be commanded. The PDM will then supply battery voltage and ground to the appropriate control circuits for the direction selected.

Memory Mirror System Operation

Mirror position is determined by both horizontal and vertical position sensors in each of the power mirrors. The DDM and PDM supplies a reference voltage and a low reference to these sensors and determines mirror position through the horizontal and vertical position signal circuits.

The memory switch receives power from the DDM through the battery supply voltage circuit and the DDM fuse. The DDM upon receipt of a memory switch signal input or an appropriate class 2 message from the BCM, the DDM and PDM will then supply battery voltage and ground to the appropriate power mirror motors through the mirror motor control circuits to move the mirrors to the predetermined positions.

Mirror Tilt in Reverse Operation

When the vehicle is placed in reverse and the appropriate class 2 message from the BCM and PCM is received by the DDM and PDM, the DDM and PDM will then supply battery voltage to the appropriate power mirror motors through the mirror motor control circuits to move the mirrors to the predetermined positions. The positions that are stored can be altered by starting the engine, applying the brake, placing the vehicle in reverse and controlling both the left and right mirrors to the desired positions and shifting the vehicle out of reverse. These new positions will be stored for the last memory recall that happened.

Folding Mirror System Operation

The mirror fold switch receives power through the battery supply voltage circuit and the EXT LPS fuse and a constant ground. The mirror extend and retract control circuits are connected to ground through the normally closed contacts of the mirror fold switch. When the mirror fold switch is activated, the solid state circuitry will energize either the extend or retract relay (depending on the last function) which supplies battery voltage to the fold motor through one of the control circuits. The other control circuit is connected to ground through the normally closed contacts in the mirror fold switch and the mirror extends or retracts.