Door System Diagnosis

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 are converted to power door serial data for exchange among the door modules. The DDM can also take information from modules connected to the class 2 serial data circuit and relay the command to the power door serial data link. The vehicle power mode message (ignition switch position) from the DIM is an example. The DDM periodically addresses each module on the power door serial data circuit. When a 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 requesting a response from a door module or the driver door switch assembly.

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.

TEST DESCRIPTION

Steps 1-3:

Steps 4-11:

Steps 12-19:

Steps 20-21:

The number(s) below refer to the step number(s) 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 5302.
4. The open in the power door serial data circuit is between the DDM and splice S302.
5. Loss of communications with individual door modules may be due to an unpowered module. This includes the driver door switch assembly (DDSA), which is also a module.
The rear door modules each have a seperate battery positive voltage circuit (connectors C1), but they are fed by the same 10 amp RRDR MDL fuse in the rear fuse block. A short to ground in either one of the rear door modules battery positive voltage circuits (connectors C1) may open the fuse and cause DTCs U1162 and U1163 to be set simultaneously.
6. Loss of communications with individual door modules may be due to an ungrounded module. This includes the driver door switch assembly (DDSA), which is also a module.
8. 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.
10. Operating the window and locks from the scan tool via the class 2 serial data circuit 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.
11. The driver door switch assembly (DDSA) processes driver door window and lock switch signals to the DDM. Since the DDM was proven capable in step 10, the malfunction must be due to the DDSA.
12. The following steps isolate the door module which is preventing power door serial data communications.