Door System Diagnosis

DTC U1161

CIRCUIT DESCRIPTION
The power door serial data circuit provides a means for information exchange among the vehicle door modules. Door module information on inputs and commanded outputs is converted to serial data and sent out on the power door serial data line for exchange among the door modules. The Driver Door Module (DDM) also communicates with the other vehicle modules via the Class 2 Serial Data circuit and can take the class 2 serial data information and relay it, via the power door serial data line, to the other door modules. The vehicle power mode message (ignition switch position) from the DIM is an example of class 2 communications between the DDM and the other vehicle modules. The DDM periodically addresses each door module on the power door serial data circuit. When a door module does not respond to the DDM, the DTC for that module is set.

CONDITIONS FOR RUNNING THE DTC
- Diagnostic trouble codes B1327, B1328, U1300, and U1301 do not have a current status.
- The driver door module has power.
- The driver door module has received an input, a power door serial data message, or a class 2 "wake-up" message.

CONDITIONS FOR SETTING THE DTC
A response from a door module on the power door serial data circuit is not received by the DDM within 2 seconds of the DDM request for a response from a door module or the driver door switch assembly (DDSA).

CONDITIONS FOR CLEARING THE DTC
- A current DTC will clear when a response message from the failed door module is detected or at the end of the current ignition cycle.
- A history DTC will clear upon receipt of a scan tool Clear DTCs command or after 50 OFF/ON ignition switch cycles without a repeat of a communications failure.

DIAGNOSTIC AIDS
- Loss of communications with individual door modules may be due to a malfunction of the power door serial data circuit, however, lost communications could also be due to an unpowered or ungrounded module. This includes the driver door switch assembly (DDSA), which is also a door module. In addition, the driver door module (DDM) or front passenger door module (PDM) will fail to communicate if the battery positive voltage circuit between the door module and corresponding power window sensor is shorted to ground, a condition which would open the associated door module fuse in the rear fuse block. Therefore, when directed to test the battery positive voltage circuit of the door module C1 connector, both battery positive voltage circuits of the connector must be tested for opens and shorts to ground, when it is a front door module that has lost communications.
- The rear door modules each have a separate battery positive voltage circuit, associated with door module connectors C1, however, the circuits are both fed by the same 10 amp RRDRMDL fuse located in the rear fuse block. A short to ground in either one of these rear door module battery positive voltage circuits, may open the fuse and cause DTCs U1162 and U1163 to be simultaneously set current.

TEST DESCRIPTION

Step 1 - 6:

Step 7 - 9:

Step 10 - 12:

Step 13 - 14:

Step 15 - 22:

The numbers below refer to the step numbers on the diagnostic table.
1. Diagnostic trouble codes U1161, U1162, U1163, and U1170 set simultaneously indicate a total malfunction of the power door serial data circuit.
2. When DTCs U1161, U1162, and U1163 set simultaneously but U1170 does not set, the malfunction is likely to be caused by an open in the power door serial data circuit between the DDM and splice S302.
4. This step determines if the open in the power door serial data circuit is between the DDM and splice S302.
5. This step determines if the battery positive voltage circuit between the driver door switch assembly (DDSA) and the DDM, or, between the affected door module and the fuse block, is open or shorted to ground.
6. This step determines if the battery positive voltage circuit between a front door module and the associated power window sensor is open or shorted to ground. A short to ground in this circuit would cause the corresponding front door module fuse in the rear fuse block to open and set the door module communications DTC.
9. This step determines if the power door serial data circuit is shorted to voltage or ground. The condition may be due to the wiring or due to a malfunction in one of the modules. When testing the wiring for a short, make sure there is not a module connected to the wire being tested.
11. By operating the window and locks from the scan tool via the class 2 serial data circuit, this step proves that the DDM is capable of controlling the driver door functions and isolates the cause of the malfunction to the power door serial data circuit.
12. This step determines if the driver door switch assembly (DDSA) is the cause of the malfunction. The DDSA processes driver door window and lock switch signals to the DDM and, since the DDM was proven capable in step 10, the malfunction must be due to the DDSA.
13. The following steps isolate the door module which is preventing power door serial data communications.