Circuit Description
The SBI data line is used to communicate information between the door modules. Each module connected to the SBI is assigned its own recognition code (address). This code is used to identify which modules are communicating. Modules communicate with each other by periodically sending State of Health (SOH) messages. When the ignition switch is in RUN, each module communicating on the SBI sends a State of Health (SOH) message every two seconds to ensure that the system is operating properly. When the LRDM stops communicating on the SBI, for example if the LRDM loses power or ground, the SOH message it normally sends on the SBI every two seconds disappears. The LFDM which expects to receive that SOH message, detects its absence and sets DTC U1162 current.
Conditions for Setting the DTC
- The LFDM does not receive a State of Health (SOH) message back from the LRDM.
- This DTC only sets if DTC B1982, B1983, U1300 or U1301 is not current in LFDM memory.
Action Taken When the DTC Sets
| • | DTC U1162 is stored in LFDM memory. |
| • | The LFDM uses the default values for the initialization data. |
| • | This DTC does not cause a driver warning message to appear. |
Conditions for Clearing the DTC
| • | This DTC clears (status changes from current to history) under any of the following conditions: |
| - | The LFDM detects a State of Health Message from the LRDM. |
| - | On each ignition cycle. |
| • | A history DTC clears after 50 consecutive ignition cycles if the conditions for setting the DTC are no longer present. |
| • | Current and history DTCs may be cleared using a scan tool or using the ON-Board System Diagnostic feature. |
Diagnostic Aids
| • | DTC module U1162 does not normally represent a failure within the module. |
| • | If the DTC is a history DTC, the problem may be intermittent. |
| • | A grounded CKT 2076 will set following DTCs U1161, U1162, U1163, and U1170. |
| • | An open or a high resistance wire between the LFDM and S303 will set DTCs U1161, U1162, U1163. |
| • | An open RRDR MDL fuse will set U1162 and U1163. |
| • | If CKT 840 is not the cause of an open RRDR MDL fuse, one of the rear door modules could be the cause. |
Test Description
The numbers below refer to the step numbers on the diagnostic table:
-
This steps inspects for related DTC that are set.
-
This steps inspects for a related DTC that is set.
-
This steps inspects the RRDL MDL fuse.
-
This steps inspects for battery voltage on CKT 840 at the LRDM.
-
This steps inspects for ground on CKT 551 at the LRDM.
-
This steps inspects for continuity of the simple bus interface from the LRDM to the LFDM on CKT 2076.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Power Door Diagnostic System Check performed? | -- | Go to Step 2 | |
Are DTCs U1161 and U1163 also set? | -- | Go to Step 3 | ||
Is DTC U1161 also set? | -- | Go to Step 4 | Go to Step 6 | |
Is the fuse open? | -- | Go to Step 5 | Go to Diagnostic Aids | |
5 | Repair the short to ground in CKT 840. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |
Does the voltage measure within the specified range? | 10-15 V | Go to Step 8 | Go to Step 7 | |
7 | Repair the open or the high resistance in CKT 840. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |
Using a DMM, measure resistance between LRDM harness connector C1 terminal 4 and ground. Does the resistance measure within the specified range? | 0-5 ohms | Go to Step 10 | Go to Step 9 | |
9 | Repair the open or the high resistance in CKT 551. Refer to Wiring Repairs in Wiring Systems. | -- | -- | |
Does the resistance measure within the specified range | 0-5 ohms | Go to Step 12 | Go to Step 11 | |
11 | Repair the open or the high resistance in CKT 2076. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |
12 | Replace the LRDM. Refer to Door Control Module Replacement . Did you complete the repair? | -- | -- |
