Pinpoint Test R: The Liftgate/Trunk Module (LTM) Does Not Respond To The Scan Tool

Refer to appropriate SYSTEM WIRING DIAGRAMS article, Module Communications Network for schematic and connector information.

Refer to appropriate SYSTEM WIRING DIAGRAMS article, Power Liftgate for schematic and connector information.

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 instrument cluster (IC), the accessory protocol interface module (APIM), the smart junction box (SJB), the HVAC module (if equipped), the audio control module (ACM), the audio digital signal processing (DSP) module (if equipped), the satellite digital audio receiver system (SDARS) module (if equipped), the parking aid module (PAM) (if equipped), the rear entertainment module (RETM) (if equipped), the driver seat module (DSM) (if equipped), and the dual climate control seat module (DCSM) (if equipped). Voltage for the LTM is provided by circuits SBP14 (BN/RD) and SBB59 (BU/RD). Circuit GD149 (BK/GY) provides ground.

This pinpoint test is intended to diagnose the following:

• Fuse
• Wiring, terminals or connectors
• LTM

PINPOINT TEST R: THE LIFTGATE/TRUNK MODULE (LTM) DOES NOT RESPOND TO THE SCAN TOOL 

1. R1 CHECK THE LTM VOLTAGE SUPPLY CIRCUITS FOR AN OPEN 
   • Key in OFF position.
   • Disconnect: LTM C4174a
   • Key in ON position.
   Fig 1: Measuring Voltage
   Courtesy of FORD MOTOR CO.
   • Measure the voltage between the LTM C4174a-4, circuit SBB59 (BU/RD), harness side and ground; and between the LTM C4174a-9, circuit SBP14 (BN/RD), harness side and ground.
   • Are the voltages greater than 10 volts? 
   1. YES  : Go to  R2.
   2. NO  : VERIFY the battery junction box (BJB) fuse 59 (30A) or the SJB fuse 14 (10A) is OK. If OK, REPAIR the circuit. CLEAR the DTCs. REPEAT the network test with the scan tool.
2. R2 CHECK THE LTM GROUND CIRCUIT FOR AN OPEN 
   • Key in OFF position.
   Fig 2: Measuring Resistance
   Courtesy of FORD MOTOR CO.
   • Measure the resistance between the LTM C4174a-1, circuit GD149 (BK/GY), harness side and ground.
   • Is the resistance less than 5 ohms? 
   1. YES  : Go to  R3.
   2. NO  : REPAIR the circuit. CLEAR the DTCs. REPEAT the network test with the scan tool.
3. R3 CHECK THE MS-CAN CIRCUITS BETWEEN THE LTM AND THE DATA LINK CONNECTOR (DLC) FOR AN OPEN 
   • Disconnect: LTM C4174b
   Fig 3: Measuring Resistance
   Courtesy of FORD MOTOR CO.
   • Measure the resistance between the LTM C4174b-11, circuit VDB06 (GY/OG), harness side and the DLC C251-3, circuit VDB06 (GY/OG), harness side.
   Fig 4: Measuring Resistance
   Courtesy of FORD MOTOR CO.
   • Measure the resistance between the LTM C4174b-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? 
   1. YES  : Go to  R4.
   2. NO  : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the network test with the scan tool.
4. R4 CHECK FOR CORRECT LTM OPERATION 
   • Disconnect all the LTM connectors.
   • Check for:
     • corrosion
     • damaged pins
     • pushed-out pins
   • Connect all the LTM connectors and make sure they seat correctly.
   • Operate the system and verify the concern is still present.
   • Is the concern still present? 
   1. YES  : INSTALL a new LTM. REFER to BODY CLOSURES article. CLEAR the DTCs. REPEAT the network test with the scan tool.
   2. 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.