Circuit Description
The body control module (BCM) internally grounds the door unlock relay control circuit for the door unlock relay when it receives a switched ground signal from any door lock switch or a keyless entry unlock transmission. When the BCM grounds the door unlock relay control circuit, the door unlock relay is energized and unlocks the doors.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B3809 Passenger Door Unlock relay Circuit
Conditions for Running the DTC
| • | Battery voltage is between 9-16 volts. |
| • | The DTC will set if the door unlock function is active or inactive. |
Conditions for Setting the DTC
The DTC will set if the passenger door unlock relay control circuit is shorted to ground or open for more than one second.
Action Taken When the DTC Sets
| • | If a short to ground is present on the door unlock relay control circuit, the door unlock relay will be energized and the door lock actuators will be held in the unlock position and will not lock. |
| • | If an open condition is present on the door unlock relay control circuit, the doors will lock but not unlock. |
Conditions for Clearing the DTC
When the fault is no longer present, the BCM changes the current DTC to a history DTC. The BCM will clear the history DTC after 50 fault-free ignition cycles.
Diagnostic Aids
| • | DTC B3809 could also set if the PASS UNLK relay winding is open. |
| • | If both DTC B3808 and B3809 are set as current, the battery positive voltage circuit or the Door LKS fuse could be open. If the Door LKS fuse is open, the cause is most likely one of the following: |
| - | A short to ground in the relay battery positive voltage circuit |
| - | A short to ground in the door lock/latch actuator lock or unlock control circuits |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Listen for an audible click when the rear door unlock relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
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This step tests for voltage at the coil side of the PASS UNLK relay. The Door LKS fuse supplies power to the coil side of the PASS UNLK relay.
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This step verifies that the BCM is providing ground to the PASS UNLK relay.
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This step tests if ground is constantly being applied to the PASS UNLK relay.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Door Lock/Indicator Schematics Connector End View Reference: Vehicle Access Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
Does the passenger door unlock relay turn ON and OFF with each command? | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 | |
Does the test lamp illuminate? | Go to Step 4 | Go to Step 8 | |
Does the test lamp turn ON and OFF with each command? | Go to Step 9 | Go to Step 5 | |
Does the test lamp remain illuminated without being commanded? | Go to Step 7 | Go to Step 6 | |
6 | Test the passenger door unlock relay control circuit for an open or a poor connection. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | Go to Step 14 | Go to Step 10 |
7 | Test the passenger door unlock relay control circuit for a short to ground or an open. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | Go to Step 14 | Go to Step 10 |
8 | Test for an open or short to ground in the battery positive voltage circuit of the PASS UNLK relay. Refer to Wiring Repairs. Did you complete the repair? | Go to Step 14 | Go to Step 11 |
9 | Inspect for poor connections at the PASS UNLK relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | Go to Step 14 | Go to Step 12 |
10 | Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | Go to Step 14 | Go to Step 13 |
11 | Repair the short to ground in the door lock/latch actuator lock or unlock control circuits. Refer to Wiring Repairs. Did you complete the repair? | Go to Step 14 | -- |
12 | Replace the PASS UNLK relay. Refer to Relay Replacement . Did you complete the replacement? | Go to Step 14 | -- |
13 | Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 14 | -- |
14 |
Does the DTC reset? | Go to Step 2 | System OK |
