B3128

CIRCUIT DESCRIPTION
The driver door unlock control circuit from the Body Control Module (BCM) controls the driver door unlock relay. When the BCM receives a door unlock signal, the BCM supplies battery positive voltage to the relay.

CONDITIONS FOR RUNNING THE DTC
The keyfob unlock button is pressed or a door lock switch is pressed to the unlock position for DTC B3127. The battery positive voltage supplied to the BCM is within normal operating range, 9 to 16 volts, for DTC B3128.

CONDITIONS FOR SETTING THE DTC
The driver door unlock control circuit is shorted to ground for 0.2 seconds, for DTC B3127. The driver door unlock control circuit is open or shorted to battery positive voltage for 0.2 seconds, for DTC B3128.

ACTION TAKEN WHEN THE DTC SETS
The BCM disables the door unlock output for the remainder of the ignition cycle.

CONDITIONS FOR CLEARING THE DTC
^ A current DTC B3127 or DTC B3128 clears when the malfunction is no longer present and the ignition switch is cycled.
^ All BCM history codes clear after 100 ignition cycles with no current codes active during the 100 ignition cycles.

DIAGNOSTIC AIDS
If the DTC is a history DTC, the problem may be intermittent. Refer to Diagnostic Aids for Circuit Testing and Wiring Repair procedures.

TEST DESCRIPTION

Steps 1-5:

Steps 6-13:

The numbers below refer to the step numbers on the diagnostic table.
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.
3. Verifies that the body control module is providing voltage to the driver door unlock relay.
4. Tests for an open in the ground circuit to the driver door unlock relay.
5. Tests if voltage is constantly being applied to the driver door unlock relay.