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DIAGNOSTIC ITEM 4: Diagnose shorts in the ground to CAN-C bus line.
 
 
cautionWhen servicing a CAN bus line, ground yourself by touching a metal object such as an unpainted water pipe. If you fail to do so, a component connected to the CAN bus line may be damaged.

 
 
 
 
FUNCTION
If a short to ground is present in the CAN-C lines, this diagnosis result will be set.
 
 
TROUBLE JUDGMENT CONDITIONS
If DTC U1120 is set, the ETACS-ECU determines that there is a failure.
 
 
TROUBLESHOOTING HINTS
  • Malfunction of the connector (short to ground inside connector)
  • Malfunction of the wiring harness (short to ground in the CAN-C main or sub bus lines)
  • Malfunction of the ECU (ETACS-ECU, or ECUs on CAN-C lines failed)
 
 
DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
  • MB991709: Wiring harness Set
STEP 1. Check the wiring harness between joint connector (CAN2) C-202 and ETACS-ECU connector C-411 for a short to ground. Measure the resistance at joint connector (CAN2) C-202.
(1) Disconnect joint connector (CAN2), and measure the resistance at the wiring harness side of joint connector (CAN2).
(2) Measure the resistance between joint connector (CAN2) terminal 11 and body ground.
OK: 1 kΩ or more
(3) Measure the resistance between joint connector (CAN2) terminal 22 and body ground.
OK: 1 kΩ or more
Do all the resistances measure 1 kΩ or more?
Go to Step 2.
Go to Step 8.
 
STEP 2. Check the wiring harness between joint connector (CAN2) C-202 and steering wheel sensor connector C-310 for a short to ground. Measure the resistance at joint connector (CAN2) C-202.
cautionDisconnect the negative battery terminal. For details refer to .
cautionA digital multimeter should be used. For details refer to .
cautionThe test wiring harness should be used. For details refer to .
(1) Disconnect joint connector (CAN2), and measure the resistance at the wiring harness side of joint connector (CAN2).
(2) Measure the resistance between joint connector (CAN2) terminal 9 and body ground.
OK: 1 kΩ or more
(3) Measure the resistance between joint connector (CAN2) terminal 20 and body ground.
OK: 1 kΩ or more
Do all the resistances measure 1 kΩ or more?
<FWD> : Go to Step 4.
<AWD> : Go to Step 3.
Go to Step 9.
 
STEP 3 Check the wiring harness between joint connector (CAN2) C-202 and AWD-ECU connector C-228 for a short to ground. Measure the resistance at joint connector (CAN2) C-202.
(1) Disconnect joint connector (CAN2), and measure the resistance at the wiring harness side of joint connector (CAN2).
(2) Measure the resistance between joint connector (CAN2) terminal 8 and body ground.
OK: 1 kΩ or more
(3) Measure the resistance between joint connector (CAN2) terminal 19 and body ground.
OK: 1 kΩ or more
Do all the resistances measure 1 kΩ or more?
Go to Step 4.
Go to Step 10.
 
STEP 4. Check the wiring harness between joint connector (CAN3) C-24 and ECM connector B-27 for a short to ground. Measure the resistance at joint connector (CAN3) C-24.
(1) Disconnect joint connector (CAN3), and measure the resistance at the wiring harness side of joint connector (CAN3).
(2) Measure the resistance between joint connector (CAN3) terminal 7 and body ground.
OK: 1 kΩ or more
(3) Measure the resistance between joint connector (CAN3) terminal 18 and body ground.
OK: 1 kΩ or more
Do all the resistances measure 1 kΩ or more?
<CVT> : Go to Step 5.
<M/T> : Go to Step 6.
Go to Step 11.
 
STEP 5. Check the wiring harness between joint connector (CAN3) C-24 and TCM connector C-131 for a short to ground. Measure the resistance at joint connector (CAN3) C-24.
(1) Disconnect joint connector (CAN3), and measure the resistance at the wiring harness side of joint connector (CAN3).
(2) Measure the resistance between joint connector (CAN3) terminal 5 and body ground.
OK: 1 kΩ or more
(3) Measure the resistance between joint connector (CAN3) terminal 16 and body ground.
OK: 1 kΩ or more
Do all the resistances measure 1 kΩ or more?
Go to Step 6.
Go to Step 12.
 
STEP 6. Check the wiring harness between joint connector (CAN3) C-24 and ASC-ECU connector A-03 for a short to ground. Measure the resistance at joint connector (CAN3) C-24.
(1) Disconnect joint connector (CAN3), and measure the resistance at the wiring harness side of joint connector (CAN3).
(2) Measure the resistance between joint connector (CAN3) terminal 8 and body ground.
OK: 1 kΩ or more
(3) Measure the resistance between joint connector (CAN3) terminal 19 and body ground.
OK: 1 kΩ or more
Do all the resistances measure 1 kΩ or more?
Go to Step 7.
Go to Step 13.
 
STEP 7. Check the wiring harness between joint connector (CAN3) C-24 and electric power steering-ECU connector C-144 for a short to ground. Measure the resistance at joint connector (CAN3) C-24.
cautionDisconnect the negative battery terminal. For details refer to .
cautionA digital multimeter should be used. For details refer to .
cautionThe test wiring harness should be used. For details refer to .
(1) Disconnect joint connector (CAN3), and measure the resistance at the wiring harness side of joint connector (CAN3).
(2) Measure the resistance between joint connector (CAN3) terminal 9 and body ground.
OK: 1 kΩ or more
(3) Measure the resistance between joint connector (CAN3) terminal 20 and body ground.
OK: 1 kΩ or more
Do all the resistances measure 1 kΩ or more?
Check intermediate connector C-128, and repair if necessary. If the intermediate connector is in good condition, repair the wiring harness between joint connector (CAN2) C-202 and joint connector (CAN3) C-24.
Go to Step 14.
 
STEP 8. Check the wiring harness between joint connector (CAN2) C-202 and ETACS-ECU connector C-411 for a short to ground.
cautionDisconnect the negative battery terminal. For details refer to .
cautionA digital multimeter should be used. For details refer to .
cautionThe test wiring harness should be used. For details refer to .
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
(1) Disconnect ETACS-ECU connector and joint connector (CAN2), and measure at the wiring harness side.
(2) Measure the resistance between joint connector (CAN2) terminal 11 and body ground.
OK: 1 kΩ or more
(3) Measure the resistance between joint connector (CAN2) terminal 22 and body ground.
OK: 1 kΩ or more
Do all the resistances measure 1 kΩ or more?
Check ETACS-ECU connector C-411, and repair if necessary. If the ETACS-ECU connector is in good condition, replace the ETACS-ECU.
Repair the wiring harness between ETACS-ECU connector C-411 and joint connector (CAN2) C-202.
 
STEP 9. Using scan tool MB991958, diagnose the CAN bus line. (checking the steering wheel sensor for internal short to ground)
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
cautionTo prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
(1) Disconnect steering wheel sensor connector C-310.
(2) Connect scan tool MB991958 to the data link connector. Refer to "How to connect the Scan Tool (M.U.T.-III) ."
(3) Turn the ignition switch to the "ON" position.
(4) Diagnose CAN bus lines, and check if the scan tool MB991958 screen is as shown in the figure.
OK: The display of the scan tool MB991958 is as shown in the figure.
Does scan tool MB991958 screen correspond to the illustration?
Repair the wiring harness between steering wheel sensor connector C-310 and joint connector (CAN2) C-202.
Check steering wheel sensor connector C-310, and repair if necessary. If the steering wheel sensor connector is in good condition, replace the steering wheel sensor.
 
STEP 10. Using scan tool MB991958, diagnose the CAN bus line. (checking the AWD-ECU for internal short to ground)
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
cautionTo prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
(1) Disconnect AWD-ECU connector C-228.
(2) Connect scan tool MB991958 to the data link connector. Refer to "How to connect the Scan Tool (M.U.T.-III) ."
(3) Turn the ignition switch to the "ON" position.
(4) Diagnose CAN bus lines, and check if the scan tool MB991958 screen is as shown in the figure.
OK: The display of the scan tool MB991958 is as shown in the figure.
Does scan tool MB991958 screen correspond to the illustration?
Check intermediate connector C-27, and repair if necessary. If the intermediate connector is in good condition, repair the wiring harness between AWD-ECU connector C-228 and joint connector (CAN2) C-202.
Check AWD-ECU connector C-228, and repair if necessary. If the AWD-ECU connector is in good condition, replace the AWD-ECU.
 
STEP 11. Using scan tool MB991958, diagnose the CAN bus line. (checking the ECM for internal short to ground)
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
cautionTo prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
(1) Disconnect ECM connector B-27.
(2) Connect scan tool MB991958 to the data link connector. Refer to "How to connect the Scan Tool (M.U.T.-III) ."
(3) Turn the ignition switch to the "ON" position.
(4) Diagnose CAN bus lines, and check if the scan tool MB991958 screen is as shown in the figure.
OK: The display of the scan tool MB991958 is as shown in the figure.
Does scan tool MB991958 screen correspond to the illustration?
Repair the wiring harness between ECM connector B-27 and joint connector (CAN3) C-24.
Check ECM connector B-27, and repair if necessary. If the ECM connector is in good condition, replace the ECM.
 
STEP 12. Using scan tool MB991958, diagnose the CAN bus line. (checking the TCM for internal short to ground)
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
cautionTo prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
(1) Disconnect TCM connector C-131.
(2) Connect scan tool MB991958 to the data link connector. Refer to "How to connect the Scan Tool (M.U.T.-III) ."
(3) Turn the ignition switch to the "ON" position.
(4) Diagnose CAN bus lines, and check if the scan tool MB991958 screen is as shown in the figure.
OK: The display of the scan tool MB991958 is as shown in the figure.
Does scan tool MB991958 screen correspond to the illustration?
Repair the wiring harness between TCM connector C-131 and joint connector (CAN3) C-24.
Check TCM connector C-131, and repair if necessary. If the TCM connector is in good condition, replace the TCM.
 
STEP 13. Using scan tool MB991958, diagnose the CAN bus line. (checking the ASC-ECU for internal short to ground)
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
cautionTo prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
(1) Disconnect ASC-ECU connector A-03.
(2) Connect scan tool MB991958 to the data link connector. Refer to "How to connect the Scan Tool (M.U.T.-III) ."
(3) Turn the ignition switch to the "ON" position.
(4) Diagnose CAN bus lines, and check if the scan tool MB991958 screen is as shown in the figure.
OK: The display of the scan tool MB991958 is as shown in the figure.
Does scan tool MB991958 screen correspond to the illustration?
Repair the wiring harness between ASC-ECU connector A-03 and joint connector (CAN3) C-24.
Check ASC-ECU connector A-03, and repair if necessary. If the ASC-ECU connector is in good condition, replace the ASC-ECU.
 
STEP 14. Using scan tool MB991958, diagnose the CAN bus line. (checking the electric power steering-ECU for internal short to ground)
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
cautionTo prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
(1) Disconnect electric power steering-ECU connector C-144.
(2) Connect scan tool MB991958 to the data link connector. Refer to "How to connect the Scan Tool (M.U.T.-III) ."
(3) Turn the ignition switch to the "ON" position.
(4) Diagnose CAN bus lines, and check if the scan tool MB991958 screen is as shown in the figure.
OK: The display of the scan tool MB991958 is as shown in the figure.
Does scan tool MB991958 screen correspond to the illustration?
Check intermediate connector C-146, and repair if necessary. If the intermediate connector is in good condition, repair the wiring harness between electric power steering-ECU connector C-144 and joint connector (CAN3) C-24.
Check electric power steering-ECU connector C-144, and repair if necessary. If the electric power steering-ECU connector is in good condition, replace the electric power steering-ECU.