Pinpoint Test D: The Lighting Control Module (LCM) Does Not Respond to the Scan Tool
Communications Network
Pinpoint Tests
Pinpoint Test D: The Lighting Control Module (LCM) Does Not Respond To 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 58, Lighting Control Module for schematic and connector information. Diagrams By Number
Normal Operation
The Lighting Control Module (LCM) communicates with the scan tool through the Standard Corporate Protocol (SCP) communication network. Circuits 914 (TN/OG) (SCP +) and 915 (PK/LB) (SCP-) provide the network connection to the LCM. Voltage for the LCM is provided by circuit 221 (OG/WH). Circuit 676 (PK/OG) provides ground.
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- LCM
PINPOINT TEST D: THE LCM 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.
NOTE: Failure to disconnect the battery will result in false resistance readings. Refer to Battery.
-------------------------------------------------
D1 CHECK THE LCM VOLTAGE SUPPLY CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect the scan tool cable from the Data Link Connector (DLC).
- Disconnect: LCM C2145a.
- Ignition ON.
- Measure the voltage between the LCM C2145a-13, circuit 221 (OG/WH), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to D2.
No
VERIFY the Central Junction Box (CJB) fuse 23 (10A) is OK. If OK, REPAIR the circuit. 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.
-------------------------------------------------
D2 CHECK THE LCM GROUND CIRCUITS FOR AN OPEN
- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Disconnect: LCM C2145c.
- Measure the resistance between the LCM C2145a-11, circuit 676 (PK/OG), harness side and ground; and C2145c-7, circuit 676 (PK/OG), harness side and ground.
- Are the resistances less than 5 ohms?
Yes
GO to D3.
No
REPAIR the circuit in question. CONNECT the negative battery cable. CLEAR the DTCs. REPEAT the network test with the scan tool.
-------------------------------------------------
D3 CHECK THE SCP CIRCUITS BETWEEN THE LCM AND THE DLC FOR AN OPEN
- Measure the resistance between the LCM C2145a-8, circuit 914 (TN/OG), harness side and the DLC C251-2, circuit 914 (TN/OG), harness side.
- Measure the resistance between the LCM C2145a-16, circuit 915 (PK/LB), harness side; and between the DLC C251-10, circuit 915 (PK/LB) harness side.
- Are the resistances less than 5 ohms?
Yes
CONNECT the negative battery cable. GO to D4.
No
REPAIR the circuit in question. CONNECT the negative battery cable. CLEAR the DTCs. REPEAT the network test with the scan tool.
-------------------------------------------------
D4 CHECK FOR CORRECT LCM OPERATION
- Disconnect all the LCM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the LCM 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 LCM. 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.
-------------------------------------------------