Pinpoint Test L: The Liftgate/Trunk Module (LTM) Does Not Communicate With The Scan Tool

Communications Network

Pinpoint Tests

Pinpoint Test L: The Liftgate/Trunk Module (LTM) Does Not Communicate With The Scan Tool

Refer to Wiring Diagram Set 14, Module Communications Network for schematic and connector information. Diagrams By Number

Refer to Wiring Diagram Set 109, Power Liftgate for schematic and connector information. Diagrams By Number

Normal Operation

The Liftgate/Trunk Module (LTM) communicates with the scan tool through the Medium Speed Controller Area Network (MS-CAN). Circuits VDB06 (GY/OG) (MS-CAN +) and VDB07 (VT/OG) (MS-CAN -) provide the network connection to the LTM. The LTM shares the MS-CAN with the Smart Junction Box (SJB), the Accessory Protocol Interface Module (APIM), the Audio Control Module (ACM), the HVAC module, the Driver Seat Module (DSM), the Rear Entertainment Module (RETM), the Satellite Digital Audio Receiver System (SDARS) module and the Instrument Cluster (IC). Voltage for the LTM is provided by circuits SBB29 (GY/RD) and SBP14 (BN/RD). Ground is provided by circuit GD147 (BK/VT).

This pinpoint test is intended to diagnose the following:

- Fuse
- Wiring, terminals or connectors
- LTM



PINPOINT TEST L: THE LTM DOES NOT RESPOND TO THE SCAN TOOL

NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.

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L1 CHECK THE VOLTAGE SUPPLY CIRCUIT FOR AN OPEN


- Ignition OFF.
- Disconnect: LTM C4174b.
- Ignition ON.
- Measure the voltage between the LTM C4174b-4, circuit SBB29 (GY/RD), harness side and ground; measure the voltage between the LTM C4174b-9, circuit SBP14 (BN/RD) harness side and ground.




- Are the voltages greater than 10 volts?

Yes
GO to L2.

No
VERIFY the SJB fuse 14 (10A) or BJB fuse 29 (30A) is OK. If OK, REPAIR the circuit in question. If not OK, Refer to the Wiring Diagrams to identify the possible causes of the short circuit. CLEAR the DTCs. REPEAT the network test with the scan tool.

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L2 CHECK THE GROUND CIRCUIT FOR AN OPEN


- Ignition OFF.
- Measure the resistance between the LTM C4174b-1, circuit GD147 (BK/VT), harness side and ground.




- Is the resistance less than 5 ohms?

Yes
GO to L3.

No
REPAIR the circuit. CLEAR the DTCs. REPEAT the network test with the scan tool.

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L3 CHECK THE MS-CAN CIRCUITS BETWEEN THE LTM AND THE DATA LINK CONNECTOR (DLC) FOR AN OPEN


- Disconnect: LTM C4174a.
- Measure the resistance between the LTM C4174a-11, circuit VDB06 (GY/OG), harness side and the DLC C251-3, circuit VDB06 (GY/OG), harness side.




- Measure the resistance between the LTM C4174a-10, circuit VDB07 (VT/OG), harness side and the DLC C251-11, circuit VDB07 (VT/OG), harness side.




- Are the resistances less than 5 ohms?

Yes
GO to L4.

No
REPAIR the circuit in question. CLEAR the DTCs. REPEAT the network test with the scan tool.

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L4 CHECK FOR CORRECT LTM OPERATION


- Disconnect the LTM connector.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect the LTM connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?

Yes
INSTALL a new LTM. CLEAR the DTCs. REPEAT the network test with the scan tool.

No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the network test with the scan tool.

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