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 Between Terminal 10 And Ground

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

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   • Junction block connectors C-210, C-211
     Fig 3: Identifying 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: Identifying 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: Identifying Junction Block Connector C-211

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   Fig 6: Identifying ABS-ECU Connector B-118

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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 :  Go to  Step 7.
   • NO :  Go to Step 5.
   Fig 7: Measuring Resistance Between Terminal 12 And 34 Ground

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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: Identifying 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: Identifying ABS-ECU Connector B-118

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   Fig 10: Identifying Harness Wire Connector

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

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   • Joint connectors C-23, C-101, C-105
   • Intermediate connector C-124
     Fig 12: Identifying 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: Identifying 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: Identifying ABS-ECU Connector B-118

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   Fig 15: Identifying Data Link Connector C-14

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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.