Module Communications Network System: Overview Mercury Mariner II

Vehicle communication utilizes both International Standards Organization (ISO) 9141 and controller area network (CAN) communications. ISO 9141 is used for diagnostic use only while CAN allows many modules to communicate with each other on a common network. CAN in-vehicle networking is a method for transferring data among distributed electronic modules via a serial data bus.

Without serial networking, intermodule communication requires dedicated, point to point wiring resulting in bulky, expensive, complex, and difficult to install wiring harnesses. Applying a serial data network reduces the number of wires, combining the signals on a single network. Information is sent to the individual control modules that control each function.

The vehicle has 3 module communication networks

1. ISO 9141
2. Medium speed (MS) CAN
3. High speed (HS) CAN

All 3 networks are connected to the data link connector (DLC). This makes diagnosis and testing of these systems easier by allowing one scan tool to be able to diagnose and control any module on the 3 networks from one connector. The DLC can be found under the instrument panel between the steering column and the audio control module (ACM).

Scheme 1

ISO 9141 Network Operation

The ISO 9141 communications network is a single wire network, used for diagnostic purposes only.

The ISO 9141 communications network is used for the following module

1. Parking aid module (PAM)

MS-CAN Operation

The MS-CAN communicates using bussed messages. The MS-CAN has an unshielded twisted pair cable, data bus (+) and data bus (-) circuits. In addition to scan tool communication, this network allows sharing of information between all modules on the network.

The MS-CAN is a medium speed communication network used for the following modules

1. Audio control module (ACM)
2. Front controls interface module (FCIM)
3. Front display interface module (FDIM)
4. Heating ventilation air conditioning (HVAC) module
5. Instrument cluster (IC)
6. Satellite digital audio receiver system (SDARS) module
7. Smart junction box (SJB)

HS-CAN Operation

The HS-CAN communicates using bussed messages. The HS-CAN uses an unshielded twisted pair cable, data bus (+) and data bus (-) circuits. In addition to scan tool communication, this network allows sharing of information between all modules on the network.

The HS-CAN is a high speed communication network used for the following modules

1. ABS module
2. Instrument cluster (IC)
3. Occupant classification system module (OCSM)
4. PCM
5. Power steering control module (PSCM)
6. Restraints control module (RCM)
7. 4X4 control module

The ISO 9141 communications network is a single wire network, used for diagnostic purposes only.

The ISO 9141 communications network is used for the following module

1. Parking aid module (PAM)

The MS-CAN communicates using bussed messages. The MS-CAN has an unshielded twisted pair cable, data bus (+) and data bus (-) circuits. In addition to scan tool communication, this network allows sharing of information between all modules on the network.

The MS-CAN is a medium speed communication network used for the following modules

1. Audio control module (ACM)
2. Heating ventilation air conditioning (HVAC) module
3. Front controls interface module (FCIM)
4. Front display interface module (FDIM)
5. Instrument cluster (IC)
6. Satellite digital audio receiver system (SDARS) module
7. Smart junction box (SJB)

The HS-CAN communicates using bussed messages. The HS-CAN uses an unshielded twisted pair cable, data bus (+) and data bus (-) circuits. In addition to scan tool communication, this network allows sharing of information between all modules on the network.

The HS-CAN is a high speed communication network used for the following modules

1. ABS module
2. Instrument cluster (IC)
3. Occupant classification system module (OCSM)
4. PCM
5. Power steering control module (PSCM)
6. Restraints control module (RCM)
7. Traction battery control module (TBCM)
8. Transmission control module (TCM)
9. 4X4 control module

Principles of Operation

Vehicle communication utilizes both International Standards Organization (ISO) 9141 and controller area network (CAN) communications. ISO 9141 is used for diagnostic use only, and CAN is a method for transferring data among distributed electronic modules via a serial data bus.

The vehicle is equipped with 3 module communication networks

1. ISO 9141
2. Medium speed (MS) CAN
3. High speed (HS) CAN

Normal Operation - Escape and Mariner

The PCM communicates with the scan tool through the high speed controller area network (HS-CAN). Circuits VDB04 (WH/BU) (HS-CAN +) and VDB05 (WH) (HS-CAN -) provide the network connection to the PCM. The PCM shares the HS-CAN with the ABS module, the 4X4 control module, restraints control module (RCM), occupant classification system module (OCSM), power steering control module (PSCM) and the instrument cluster (IC). Voltage for the PCM is provided by circuits CBB28 (GY/VT) and SBB05 (GY/RD). Circuit GD122 (BK) provides ground.

Normal Operation - Hybrid

The PCM communicates with the scan tool through the high speed controller area network (HS-CAN). Circuits VDB04 (WH/BU) (HS-CAN +) and VDB05 (WH) (HS-CAN -) provide the network connection to the PCM. The PCM shares the HS-CAN with the ABS module, restraints control module (RCM), occupant classification system module (OCSM), power steering control module (PSCM), transmission control module (TCM), traction battery control module (TBCM) and the instrument cluster (IC). Voltage for the PCM is provided by circuits CBB29 (WH/VT) and SBB05 (GY/RD). Circuit GD122 (BK) provides ground.

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. ABS module
4. 4X4 control module (if equipped)
5. IC
6. PCM
7. RCM
8. PSCM
9. OCSM
10. TCM (Hybrid only)
11. TBCM (Hybrid only)

The ABS module communicates with the scan tool through the high speed controller area network (HS-CAN). Circuits VDB04 (WH/BU) (HS-CAN +) and VDB05 (WH) (HS-CAN -) provide the network connection to the ABS module. The ABS module shares the HS-CAN with the PCM, the 4X4 control module, the instrument cluster (IC), the restraints control module (RCM), the power steering control module (PSCM) and the occupant classification system module (OCSM). Voltage for the ABS module is provided by circuits CBP34 (VT/BN), SBB09 (RD) and SBB18 (YE/RD). Ground is provided by circuit GD120 (BK/GN).

The ABS module communicates with the scan tool through the high speed controller area network (HS-CAN). Circuits VDB04 (WH/BU) (HS-CAN +) and VDB05 (WH) (HS-CAN -) provide the network connection to the ABS module. The ABS module shares the HS-CAN with the PCM, the instrument cluster (IC), the restraints control module (RCM), the power steering control module (PSCM), the transmission control module (TCM), the traction battery control module (TBCM) and the occupant classification system module (OCSM). Voltage for the ABS module is provided by circuits CBP34 (VT/BN), SBB06 (BN/RD), SBB09 (RD) and SBB18 (YE/RD). Ground is provided by circuit GD113 (BK/YE) and GD179 (BK/VT) .

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. ABS module

Normal Operation

The 4X4 control module communicates with the scan tool through the high speed controller area network (HS-CAN). Circuits VDB04 (WH/BU) (HS-CAN +) and VDB05 (WH) (HS-CAN -) provide the network connection to the 4X4 control module. The 4X4 control module shares the HS-CAN with the PCM, the ABS module, the instrument cluster (IC), the restraints control module (RCM), the power steering control module (PSCM) and the occupant classification system module (OCSM). Voltage for the 4X4 control module is provided by circuits CBP35 (YE/GY) and SBP11 (BU/RD). Ground is provided by circuit GD182 (BK/GY).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. 4X4 control module

The instrument cluster (IC) communicates with the scan tool through the high speed controller area network (HS-CAN). Circuits VDB04 (WH/BU) (HS-CAN +) and VDB05 (WH) (HS-CAN -) provide the HS-CAN connection to the IC and circuits VDB06 (GY/OG) (MS-CAN +) and VDB07 (VT/OG) (MS-CAN -) provide the medium speed controller area network (MS-CAN) connection to the IC. The IC shares the HS-CAN with the PCM, the ABS module, the 4X4 control module, the restraints control module (RCM), the power steering control module (PSCM) and the occupant classification system module (OCSM). For Hybrid vehicles, the IC also shares the HS-CAN with the transmission control module (TCM) and traction battery control module (TBCM).

The IC shares the MS-CAN with the smart junction box (SJB), the heating ventilation air conditioning (HVAC) module, the audio control module (ACM), the satellite digital audio receiver system (SDARS) module, the front controls interface module (FCIM) and front display interface module (FDIM). Voltage for the IC is provided by circuits CBP29 (WH/VT), and SBP26 (YE/RD). Circuits GD112 (BK/GN) and GD114 (BK/BU) provide ground.

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. IC

The restraints control module (RCM) communicates with the scan tool through the high speed controller area network (HS-CAN). Circuits VDB04 (WH/BU) (HS-CAN +) and VDB05 (WH) (HS-CAN -) provide the HS-CAN connection to the RCM. The RCM shares the HS-CAN with the PCM, the ABS module, the 4X4 control module, the instrument cluster (IC), the power steering control module (PSCM) and the occupant classification system module (OCSM). For Hybrid vehicles, the IC also shares the HS-CAN with the transmission control module (TCM) and traction battery control module (TBCM). Voltage for the RCM is provided by circuits CBP32 (GN/VT) and the RCM is case grounded.

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. RCM

The occupant classification system module (OCSM) communicates with the scan tool through the high speed controller area network (HS-CAN). Circuits VDB04 (WH/BU) (HS-CAN +) and VDB05 (WH) (HS-CAN -) provide the HS-CAN connection to the OCSM. The OCSM shares the HS-CAN with the PCM, the ABS module, the 4X4 control module, the instrument cluster (IC), the power steering control module (PSCM) and the restraints control module (RCM). For Hybrid vehicles, the IC also shares the HS-CAN with the transmission control module (TCM) and traction battery control module (TBCM). Voltage for the OCSM is provided by circuit CBP46 (WH/BU) and circuit GD183 (BK/WH) provides ground.

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. OCSM

The power steering control module (PSCM) communicates with the scan tool through the high speed controller area network (HS-CAN). Circuits VDB04 (WH/BU) (HS-CAN +) and VDB05 (WH) (HS-CAN -) provide the HS-CAN connection to the PSCM. The PSCM shares the HS-CAN with the PCM, the ABS module, the 4X4 control module, the instrument cluster (IC), the occupant classification system module (OCSM) and the restraints control module (RCM). For Hybrid vehicles, the IC also shares the HS-CAN with the transmission control module (TCM) and traction battery control module (TBCM). Voltage for the power steering control module (PSCM) is provided by circuit CBP35 (YE/GY) and circuit GD116 (BK/VT) provides ground.

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. PSCM

The transmission control module (TCM) is present on Hybrid vehicles only. The TCM communicates with the scan tool through the high speed controller area network (HS-CAN). Circuits VDB04 (WH/BU) (HS-CAN +) and VDB05 (WH) (HS-CAN -) provide the network connection to the TCM. The TCM shares the HS-CAN with the PCM, the traction battery control module (TBCM), the ABS module, the power steering control module (PSCM), restraints control module (RCM), occupant classification system module (OCSM) and the instrument cluster (IC). Voltage for the TCM is provided by circuits CBB27 (GN/BN) and SBB08 (VT/RD). Ground is provided by circuit GD121 (BK/YE).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. TCM

Scheme 2

1. H1 CHECK THE POWER TO THE TCM Key in OFF position. Disconnect: TCM C1458a Key in ON position. Measure the voltage between the TCM, harness side and ground as follows: Connector-Pin Circuit C1458a-4 CBB27 (GN/BN) C1458a-5 CBB27 (GN/BN) C1458a-12 SBB08 (VT/RD) Are the voltages greater than 10 volts? YES : Go to H2 . NO : VERIFY the battery junction box (BJB) fuse 27 (10A) or fuse 8 (5A) is OK. If OK, REPAIR the circuit in question. CLEAR the DTCs. REPEAT the network test with the scan tool.
2. H2 CHECK THE TCM GROUNDS Key in OFF position. Measure the resistance between the TCM harness side and ground as follows: Connector-Pin Circuit C1458a-2 GD121 (BK/YE) C1458a-8 GD121 (BK/YE) Are the resistances less than 5 ohms? YES : Go to H3 . NO : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the network test with the scan tool.
3. H3 CHECK THE HS-CAN CIRCUITS BETWEEN THE TCM AND THE DATA LINK CONNECTOR (DLC) FOR AN OPEN Measure the resistance between the TCM C1458a-1, circuit VDB04 (WH/BU), harness side and the DLC C251-6, circuit VDB04 (WH/BU), harness side; and between the TCM C1458a-7, circuit VDB05 (WH), harness side and the DLC C251-14, circuit VDB05 (WH), harness side. Are the resistances less than 5 ohms? YES : Go to H4 . NO : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the network test with the scan tool.
4. H4 CHECK FOR CORRECT TCM OPERATION Disconnect the TCM connector. Check for: corrosion damaged pins pushed-out pins Connect the TCM connector and make sure it seats correctly. Operate the system and verify the concern is still present. Is the concern still present? YES : INSTALL a new TCM. REFER to «AUTOMATIC TRANSAXLE/TRANSMISSION - ELECTRONICALLY CONTROLLED CONTINUOUSLY VARIABLE TRANSMISSION (ECVT)»(ref-292153) article. 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.

The traction battery control module (TBCM) is present on Hybrid vehicles only. The TBCM communicates with the scan tool through the high speed controller area network (HS-CAN). Circuits VDB04 (WH/BU) (HS-CAN +) and VDB05 (WH) (HS-CAN -) provide the network connection to the TBCM. The TBCM shares the HS-CAN with the PCM, the transmission control module (TCM), the ABS module, the power steering control module (PSCM), restraints control module (RCM), occupant classification system module (OCSM), and the instrument cluster (IC). Voltage for the TBCM is provided by circuits CBB23 (BN/YE), SBB05 (GY/RD) and SBB15 (WH/RD). Ground is provided by circuits GD182 (BK/GY) and GD149 (BK/GY).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. TBCM

Scheme 3

1. I1 CHECK THE POWER TO THE TBCM WARNING: When servicing the high-voltage system, establish a buffer zone per the specified procedure. Failure to follow this instruction may result in serious personal injury or death. WARNING: Turn OFF the ignition switch for a minimum of 5 minutes before removing high-voltage cables. High-voltage cables and wiring are orange in color. The nominal high-voltage traction battery voltage (HVTB) is 330 V DC. Failure to follow these instructions may result in serious personal injury or death. WARNING: Depower the high-voltage traction battery (HVTB) before carrying out any removal or installation procedures affecting the high-voltage battery system. Failure to follow this instruction may result in serious personal injury or death. WARNING: Wear high-voltage insulated safety gloves and a face shield when working with high-voltage batteries or cables. The high-voltage insulated safety gloves should be of the appropriate safety and protection rating. Inspect the gloves before use and always wear them with the leather outer glove. Any hole in the rubber insulating glove is a potential entry point for high-voltage. Failure to follow these instructions may result in serious personal injury or death. Key in OFF position. Disconnect: TBCM C4227a Key in ON position. Measure the voltage between the TBCM, harness side and ground as follows: Connector-Pin Circuit C4227a-4 SBB15 (WH/RD) C4227a-5 SBB15 (WH/RD) C4227a-6 SBB15 (WH/RD) C4227a-10 SBB05 (GY/RD) C4227a-11 SBB05 (GY/RD) C4227a-19 CBB23 (BN/YE) Are the voltages greater than 10 volts? YES : Go to I2 . NO : VERIFY the battery junction box (BJB) fuse 5 (10A), fuse 23 (5A), and fuse 15 (50A) are OK. If OK, REPAIR the circuit in question. CLEAR the DTCs. REPEAT the network test with the scan tool.
2. I2 CHECK THE TBCM GROUNDS Key in OFF position. Measure the resistance between the TBCM, harness side and ground as follows: Connector-Pin Circuit C4227a-30 GD182 (BK/GY) C4227a-31 GD182 (BK/GY) C4227a-35 GD149 (BK/GY) C4227a-36 GD149 (BK/GY) C4227a-37 GD149 (BK/GY) Are the resistances less than 5 ohms? YES : Go to I3 . NO : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the network test with the scan tool.
3. I3 CHECK THE HS-CAN CIRCUITS BETWEEN THE TBCM AND THE DATA LINK CONNECTOR (DLC) FOR AN OPEN Measure the resistance between the TBCM C4227a-29, circuit VDB04 (WH/BU), harness side and the DLC C251-6, circuit VDB04 (WH/BU), harness side; and between the TBCM C4227a-28, circuit VDB05 (WH), harness side and the DLC C251-14, circuit VDB05 (WH), harness side. Are the resistances less than 5 ohms? YES : Go to I4 . NO : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the network test with the scan tool.
4. I4 CHECK FOR CORRECT TBCM OPERATION NOTE: Do not disconnect the high voltage cables or connectors in the following step. Disconnect the TBCM connector. Check for: corrosion damaged pins pushed-out pins Connect the TBCM connector and make sure it seats correctly. Operate the system and verify the concern is still present. Is the concern still present? YES : INSTALL a new high voltage traction battery. REFER to «HIGH VOLTAGE TRACTION BATTERY»(ref-292193) article. 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.

The smart junction box (SJB) 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 SJB. The SJB shares the MS-CAN with the instrument cluster (IC), audio control module (ACM), heating ventilation air conditioning (HVAC) module, satellite digital audio receiver system (SDARS) module, front controls interface module (FCIM) and front display interface module (FDIM). Voltage for the SJB is provided directly from the internal SJB busbar through SJB fuse 5 (10A). Ground is provided by circuit GD182 (BK/GY).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. SJB

The audio control module (ACM) 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 ACM . The ACM shares the MS-CAN with the instrument cluster (IC), smart junction box (SJB), heating ventilation air conditioning (HVAC) module, satellite digital audio receiver system (SDARS) module, front controls interface module (FCIM) and front display interface module (FDIM). Voltage for the ACM is provided by circuit SBP39 (WH/RD). Ground is provided by circuit GD115 (BK/GY).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. ACM

The heating ventilation air conditioning (HVAC) module 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 HVAC module. The HVAC module shares the MS-CAN with the instrument cluster (IC), smart junction box (SJB), audio control module (ACM), satellite digital audio receiver system (SDARS) module, front controls interface module (FCIM) and front display interface module (FDIM). Voltage to the HVAC module is provided by circuit SBP15 (WH/RD) and circuit CBP37 (WH). Ground is provided by circuit GD114 (BK/BU).

Note. The electronic manual temperature control (EMTC) HVAC module does not communicate with the scan tool.

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. HVAC module

The satellite digital audio receiver system (SDARS) module 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 SDARS module. The SDARS module shares the MS-CAN with the instrument cluster (IC), smart junction box (SJB), heating ventilation air conditioning (HVAC) module, audio control module (ACM), front controls interface module (FCIM) and front display interface module (FDIM). Voltage to the SDARS module is provided by circuit SBP14 (BN/RD). Ground is provided by circuit GD115 (BK/GY).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. SDARS module

The front display interface module (FDIM) 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 front display interface module. The FDIM shares the MS-CAN with the instrument cluster (IC), smart junction box (SJB), heating ventilation air conditioning (HVAC) module, audio control module (ACM), front controls interface module (FCIM) and satellite digital audio receiver system (SDARS) module. Voltage to the FDIM is provided by circuit SBP14 (BN/RD). Ground is provided by circuit GD114 (BK/BU).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. FDIM

The front controls interface module (FCIM) 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 FCIM. The FCIM shares the MS-CAN with the instrument cluster (IC), smart junction box (SJB), heating ventilation air conditioning (HVAC) module, audio control module (ACM), front display interface module (FDIM) and satellite digital audio receiver system (SDARS) module. Voltage to the FCIM is provided by circuit SBP14 (BN/RD). Ground is provided by circuit GD115 (BK/GY).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. FCIM

The parking aid module (PAM) communicates with the scan tool through the ISO 9141 communications network, circuit VDB10 (GY). The PAM is the only module which communicates on the ISO 9141. Voltage for the PAM is provided by circuit CBP35 (YE/GY). Ground is provided by circuit GD182 (BK/GY).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. PAM

The medium speed controller area network (MS-CAN) uses an unshielded twisted pair cable, circuits VDB06 (GY/OG) and VDB07 (VT/OG). The smart junction box (SJB), audio control module (ACM), heating ventilation air conditioning (HVAC) module, satellite digital audio receiver system (SDARS) module, front display interface module (FDIM) and front controls interface module (FCIM) communicate with the scan tool using the MS-CAN. The instrument cluster (IC), while on the MS-CAN, communicates with the scan tool only on the high speed controller area network (HS-CAN).

This pinpoint test is intended to diagnose the following

1. Wiring, terminals or connectors
2. IC
3. SJB
4. ACM
5. FCIM (if equipped)
6. HVAC module (if equipped)
7. SDARS module (if equipped)
8. FDIM

The scan tool is connected to the data link connector (DLC) to communicate with the high speed controller area network (HS-CAN), medium speed controller area network (MS-CAN), and International Standards Organization (ISO) 9141 communications network. Voltage for the scan tool is provided by circuit SBP20 (GN/RD). Ground is provided by circuits GD112 (BK/GN) and GD114 (BK/BU).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. DLC

Scheme 4

Scheme 5

Scheme 6

1. R1 CHECK DLC PINS FOR DAMAGE NOTE: Most faults are due to connector and/or wiring concerns. Carry out a thorough inspection and verification before proceeding with the Pinpoint Test. Disconnect the scan tool cable from the DLC. Inspect the DLC pins 4, 5 and 16 for damage. Are the DLC pins 4, 5 and 16 OK? YES : Go to R2 . NO : REPAIR the DLC as necessary. REPEAT the network test with the scan tool.
2. R2 CHECK THE VOLTAGE TO THE SCAN TOOL CIRCUIT 956 (OG/LG) Measure the voltage between the DLC C251-16, circuit SBP20 (GN/RD), harness side and ground. Is the voltage greater than 10 volts? YES : Go to R3 . NO : VERIFY the smart junction box (SJB) fuse 20 (15A) is OK. If OK, REPAIR the circuit. REPEAT the network test with the scan tool.
3. R3 CHECK THE DLC GROUND CIRCUITS FOR AN OPEN Measure the resistance between the DLC C251-4, circuit GD112 (BK/GN), harness side and ground; and between the DLC C251-5, circuit GD114 (BK/BU), harness side and ground. Are the resistances less than 5 ohms? YES : REPAIR the scan tool. REPEAT the network test with the scan tool. NO : REPAIR the circuit in question. REPEAT the network test with the scan tool.