Door System, Mirror System & Window System: Overview Chevrolet Silverado 1500

Test Description

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

1. 2: Listen for an audible click when the driver 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 driver door unlock relay. The LOCKS fuse supplies power to the coil side of the driver door unlock relay.
3. 4: Verifies that the body control module is providing ground to the driver door unlock relay.
4. 5: Tests if ground is constantly being applied to the driver door unlock relay.

DTC B1017 or B3970

The numbers below refer to the step numbers 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.

DTC B3808

The numbers below refer to the step numbers 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.

DTC B3809

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.

DTC B3819

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.

DTC B3820

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.

DTC B3822

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.

DTC B3823

Door Description

The hinges are welded to the door and to the body. There is no adjustment to this type of hinge. The replacement hinges bolt to the door and to the body side pillar. The replacement hinges are adjustable.

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 driver power window is unique from the passenger power windows in that it does not use window up and down relays. The driver power window is operated directly from the power window switch.

The normally closed contacts of the switch are connected to ground and the center pole is connected to the RAP fuse supply voltage circuit. By placing the left power window switch in the down position, voltage is applied to the power window motor left front down circuit and to the power window motor. The other side of the power window motor is connected to ground through the normally closed contacts of the left power window switch through the power window motor left front up circuit and drives the window down.

By placing the left power window switch in the up position the polarity of the motor is reversed and the motor drives the window up.

Passenger Power Window Operation

The passenger power window switches incorporate window up and down relays. The relay coil feed and supply sides are powered through the RAP fuse supply voltage circuit. 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 up and down relay control circuits are connected to the normally closed contacts of the passenger window switch. These contacts are wired in series with the power window master switch, through the power window master switch up and down signal circuits and then to ground when the power window master is placed in the up or down position. This allows for the up and down operation of the passenger power window from the power window master switch. The center pole of the passenger power window switch is also connected to ground and will energize the relay when placed in the up or down position.

Express Down Operation

Vehicles equipped with the express down function incorporate an auto down module in the power window master switch. The auto down module senses the operation of the LF window switch and controls voltage and ground availability to the power window up and down circuits.

When the LF power window switch is held in the down position for more then 1 second, the auto down module supplies voltage to the power window down circuit continuously until the power window reaches the bottom of its travel. At this point, the auto down module senses an over current situation on the power window down circuit and interrupts the voltage supply. If the LF power window switch is actuated less then 1 second, the operation is the same except the power window down circuit will be interrupted when the switch is released.

Driver, Passenger and Cargo Door Lock System Operation

The front power door lock switches are integral components of the driver door module (DDM) and passenger door module (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 rear door lock switch provides a lock and unlock signal to the body control module (BCM). The BCM upon receipt of a lock or unlock signal will control the rear door lock relays and also send a Class 2 message to the DDM and PDM to perform the appropriate function.

The modules which activate the power lock motors are

1. The DDM (driver door lock actuator).
2. The PDM (passenger front door lock actuator).
3. The BCM (both rear door lock actuators and cargo door/liftgate).

The DDM and PDM 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 passenger and cargo 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.

Liftgate Locking Operation

The liftgate will lock any time the vehicle is shifted out of park on vehicles equipped with an automatic transmission and at vehicle speeds exceeding 5 kph with manual transmission. This happens in conjunction with auto door locks if enabled or independently of auto door locks if the feature is disabled. This ensures that the liftgate is locked anytime the vehicle is shifted out of park or when the vehicle is in motion.

The liftgate lock relay supply and coil sides receive a constant voltage through the battery voltage supply circuit and the ECC fuse. The normally closed contact is connected to ground and the control side is connected to the body control module (BCM). A lock function will occur when a door lock switch activation, keyless entry lock transmission, auto door lock function or a liftgate lock function has been received by the BCM. The BCM will then ground the control side of the liftgate lock relay. This energizes the relay and allows voltage to be applied to the liftgate lock actuator lock control circuit. Since the other side of the liftgate lock actuator is connected to the normally closed contacts of the door unlock relay to ground, the liftgate will lock. When an unlock function occurs the BCM will ground the control side of the unlock relay and the rear doors and liftgate will unlock.

The BCM also runs diagnostics on the liftgate lock relay control circuit and will set DTC B3825 as current and also send a Class 2 message to the DIC. The DIC will display REPLACE LIFTGATE FUSE to inform the driver that a fault has been detected in the liftgate lock circuit and that the liftgate is not locked. Faults that will set the DTC and cause the DIC to display the message could be any of the following

1. An open ECC fuse
2. An open or short to ground in the liftgate lock relay battery positive voltage circuit
3. A faulty liftgate lock relay
4. An open or short to ground in the liftgate lock relay control circuit
5. A short to ground in the liftgate lock actuator lock control circuit
6. A faulty BCM

Delayed Locking Operation

With any door open and a door lock switch is activated in the lock position, the driver door module (DDM), passenger door module (PDM) and the body control module (BCM) will go into a lock pending state. The BCM will also give three audible chimes. When the door is closed, the DDM, PDM and the BCM will lock the doors after approximately five seconds. This feature can be overridden by activating the door lock switch a second time and the doors will lock even with a door open.

Power Mirror System Operation

The power mirror switch is integrated into the DDM. The left and right mirror positions of the select switch and 4 positions of the direction switch, when active, will provide a signal to the DDM. If the selector switch is placed in the L position and the up switch is depressed, 2 signals will be supplied to the DDM. 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 is received by the DDM and PDM, 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. 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 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

Upon receipt of the required switch inputs the DDM will supply battery voltage and ground to the mirror fold motor control circuits to perform the requested extend or retract function. The DDM will also send a class 2 message to the PDM indicating the requested function. The PDM will supply battery voltage and ground to the mirror fold motor control circuits to perform the requested extend or retract function.