INSPECTION PROCEDURE 2: Communication between the Scan Tool and the ABS-ECU is not possible.: Diagnosis

Required Special Tool: 

• MB991223: Harness Set

1. STEP 1. Check the power supply circuit. Measure the voltage at ABS-ECU connector B-118. 
   1. Disconnect ABS-ECU connector B-118 and measure at the harness side.
   2. Start the engine.
   3. Measure the voltage between terminal 10 and ground. It should measure battery voltage (approximately 12 volts).

   Q: Is battery positive voltage (approximately 12 volts) present? 

   YES:  Go to step  4.

   NO:  Go to step 2.

   Fig 1: Measuring Voltage At ABS-ECU Connector B-118

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2. STEP 2. Check the following connectors. 
   • ABS-ECU connector B-118
     Fig 2: Checking ABS-ECU Connector B-118

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   • Junction block connectors C-210, C-211
     Fig 3: Checking Junction Block Connectors C-210, C-211

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   • Intermediate connector C-124

   Check the connectors, for loose, corroded or damaged terminals, or terminals pushed back in the connector.

   Q: Are the connectors and terminals in good condition? 

   YES:  Go to step 3.

   NO:  Repair it and then Go to step  9.

   Fig 4: Checking Intermediate Connector C-124

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3. STEP 3. Check the following harness wire. 
   • The wire between junction block connector C-211 (terminal 2) and ABS-ECU connector B-118 (terminal 10)

   Q: Is the harness wire damaged? 

   YES:  Repair or replace it and then Go to step  9.

   NO:  Go to step  9.

   Fig 5: Checking Junction Block Connector C-211 (Terminal 2)

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   Fig 6: Checking ABS-ECU Connector B-118 (Terminal 10)

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4. STEP 4. Check the ground circuit. Measure the resistance at ABS-ECU connector B-118. 

   Measure the resistance between terminal 12 and ground, and terminal 34 and ground. It should measure less than 2 ohms.

   Q: Is the resistance 2 ohms or less? 

   YES:  Replace the scan tool and then Go to step  7.

   NO:  Go to step 5.

   Fig 7: Measuring Resistance At ABS-ECU Connector B-118

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5. STEP 5. Check the following connector. 
   • ABS-ECU connector B-118

   Check the connector, for loose, corroded or damaged terminals, or terminals pushed back in the connector.

   Q: Are the connector and terminals in good condition? 

   YES:  Go to step 6.

   NO:  Repair it and then Go to step  9.

   Fig 8: Checking ABS-ECU Connector B-118

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6. STEP 6. Check the following harness wires. 
   • The wire between ABS-ECU connector B-118 (terminal 12) and ground (No. 14)
   • The wire between ABS-ECU connector B-118 (terminal 34) and ground (No. 14)

   Q: Is any harness wire damaged? 

   YES:  Repair or replace it and then Go to step  9.

   NO:  Go to step  9.

   Fig 9: Checking ABS-ECU Connector B-118 (Terminal 12 And 34)

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   Fig 10: Checking Ground (No. 14)

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7. STEP 7. Check the following connectors. 
   • Data link connector C-14
     Fig 11: Checking Data Link Connector C-14

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   • Joint connectors C-23, C-101, C-105
   • Intermediate connector C-124
     Fig 12: Checking Joint Connectors C-23, C-101, C-105 And Intermediate Connector C-124

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   • ABS-ECU connector B-118

   Check the connectors, for loose, corroded or damaged terminals, or terminals pushed back in the connector.

   Q: Are the connectors and terminals in good condition? 

   YES:  Go to step 8.

   NO:  Repair it and then Go to step  9.

   Fig 13: Checking ABS-ECU Connector B-118

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8. STEP 8. Check the following harness wires. 
   • The wire between ABS-ECU connector B-118 (terminal 2) and data link connector C-14 (terminal 7)
   • The wire between ABS-ECU connector B-118 (terminal 5) and data link connector C-14 (terminal 1)

   Q: Is any harness wire damaged? 

   YES:  Repair or replace it and then Go to step 9.

   NO:  Replace the brake modulator hydraulic unit (integrated with ABS-ECU) (Refer to HYDRAULIC UNIT  ). Then Go to step 9.

   Fig 14: Checking ABS-ECU Connector B-118 (Terminal 2 And 5)

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   Fig 15: Checking Data Link Connector C-14 (Terminal 7 And 1)

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9. STEP 9. Retest the system. 

   Q: Does the scan tool communicate with the ABS system? 

   YES:  The procedure is complete.

   NO:  Return to Step  1.