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DIAGNOSTIC ITEM 4: Diagnose shorts in the ground to CAN bus line [CAN-C (Main)].
 
 
cautionWhen servicing a CAN bus line, ground yourself by touching a metal object such as an unpainted water pipe. If you fail to do, a component connected to the CAN bus line may be broken.
 
 
 
 
TROUBLE JUDGEMENT CONDITIONS
The scan tool MB991958 judges the trouble when it is impossible to receive the periodically sent data and the voltage of CAN_H or CAN_L line is less than 1.0 volt.
 
 
TROUBLESHOOTING HINTS
  • Malfunction of the wiring harness
  • Malfunction of the connector
  • Malfunction of the ETACS-ECU
  • Malfunction of the steering column switch (steering wheel sensor)
  • Malfunction of the AWD-ECU <AWD>
  • Malfunction of the occupant classification-ECU
  • Malfunction of the FCM/LDW/AHB-ECU <Vehicles with FCM>
  • Malfunction of the SRS-ECU
  • Malfunction of the TCM
  • Malfunction of the ASC-ECU
  • Malfunction of the EPS-ECU
  • Malfunction of the ECM
  • Malfunction of the gateway-ECU
 
 
DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
STEP 1. Check the CAN-C (Main) bus line. Resistance measurement at gateway-ECU connector C-49.
caution
  • A digital multimeter should be used. For details refer to .
  • The test wiring harness should be used. For details refer to .
  • When measuring the resistance, disconnect the negative battery terminal. For details refer to .
noteThis inspection allows you to check that there is a short to power supply in either CAN_H line or CAN_L line. Thus, in the following steps, check the CAN-C that is defective.
(1) Disconnect ECM connector B-27, ETACS-ECU connector C-411 and gateway-ECU connector C-49, and measure the resistance at the harness side of gateway-ECU connector C-49.
(2) Ensure that the negative battery terminal is disconnected.
(3) Resistance between gateway-ECU connector C-49 terminal No.3 (CAN_H) and body ground
OK: 1 kΩ or more
(4) Resistance between gateway-ECU connector C-49 terminal No.2 (CAN_L) and body ground
OK: 1 kΩ or more
Is the check result normal?
<Both of the measurement results show 1 kΩ or more> Go to Step 30.
<Either of CAN_H line or CAN_L line the measurement results show less than 1 kΩ> Go to Step 2.
 
STEP 2. Check the CAN-C (Main) bus line. Resistance measurement at intermediate connector C-128.
caution
  • A digital multimeter should be used. For details refer to .
  • The test wiring harness should be used. For details refer to .
  • When measuring the resistance, disconnect the negative battery terminal. For details refer to .
(1) Disconnect the intermediate connector C-128, and measure at its female-side intermediate connector (at the front wiring harness side).
(2) Ensure that the negative battery terminal is disconnected.
(3) Resistance between intermediate connector C-128 terminal No.13 (CAN_H) and body ground
OK: 1 kΩ or more
(4) Resistance between intermediate connector C-128 terminal No.14 (CAN_L) and body ground
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Go to Step 13.
<Less than 1 kΩ> Go to Step 3.
 
STEP 3. Check the CAN-C (Main) bus line between joint connector (CAN3) C-24 and the ECM connector B-27. Resistance measurement at joint connector (CAN3) C-24.
caution
  • A digital multimeter should be used. For details refer to .
  • The test wiring harness should be used. For details refer to .
  • When measuring the resistance, disconnect the negative battery terminal. For details refer to .
  • Strictly observe the specified wiring harness repair procedure. For details refer to .
(1) Disconnect joint connector (CAN3) C-24, and measure at the wiring harness side.
(2) Ensure that the negative battery terminal is disconnected.
(3) Resistance between joint connector (CAN3) C-24 terminal No.7 (CAN_H) and body ground
OK: 1 kΩ or more
(4) Resistance between joint connector (CAN3) C-24 terminal No.18 (CAN_L) and body ground
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Go to Step 4.
<Less than 1 kΩ> Repair the wiring harness between joint connector (CAN3) C-24 and the ECM connector B-27.
 
STEP 4. Check the CAN-C (Main) bus line between joint connector (CAN3) C-24 and the TCM connector C-131. Resistance measurement at joint connector (CAN3) C-24.
caution
  • A digital multimeter should be used. For details refer to .
  • The test wiring harness should be used. For details refer to .
  • When measuring the resistance, disconnect the negative battery terminal. For details refer to .
(1) Disconnect joint connector (CAN3) C-24, and measure at the wiring harness side.
(2) Ensure that the negative battery terminal is disconnected.
(3) Resistance between joint connector (CAN3) C-24 terminal No.5 (CAN_H) and body ground
OK: 1 kΩ or more
(4) Resistance between joint connector (CAN3) C-24 terminal No.16 (CAN_L) and body ground
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Go to Step 7.
<Less than 1 kΩ> Go to Step 5.
 
STEP 5. Scan tool MB991958 CAN bus diagnostics [TCM connector C-131 disconnected]
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
(1) Disconnect TCM connector C-131 and read all diagnosis with scan tool MB991958.
(2) Confirm that all diagnosis reading results are as shown in the table.
Are all diagnosis reading results as shown in the table?
Repair the wiring harness between joint connector (CAN3) C-24 and the TCM connector C-131.
Check the TCM connector C-131, and repair if necessary. If the TCM connector C-131 is in good condition, go to Step 6.
 
STEP 6. Scan tool MB991958 CAN bus diagnostics (retest the system)
Diagnose CAN-C (Main) bus line, and check if scan tool MB991958 screen shows normal state.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
Check the TCM connector C-131, and repair if necessary. If the TCM connector C-131 is in good condition, replace the TCM.
 
STEP 7. Check the CAN-C (Main) bus line between joint connector (CAN3) C-24 and the ASC-ECU connector A-03. Resistance measurement at joint connector (CAN3) C-24.
caution
  • A digital multimeter should be used. For details refer to .
  • The test wiring harness should be used. For details refer to .
  • When measuring the resistance, disconnect the negative battery terminal. For details refer to .
(1) Disconnect joint connector (CAN3) C-24, and measure at the wiring harness side.
(2) Ensure that the negative battery terminal is disconnected.
(3) Resistance between joint connector (CAN3) C-24 terminal No.8 (CAN_H) and body ground
OK: 1 kΩ or more
(4) Resistance between joint connector (CAN3) C-24 terminal No.19 (CAN_L) and body ground
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Go to Step 10.
<Less than 1 kΩ> Go to Step 8.
 
STEP 8. Scan tool MB991958 CAN bus diagnostics [ASC-ECU connector A-03 disconnected]
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
(1) Disconnect ASC-ECU connector A-03 and read all diagnosis with scan tool MB991958.
(2) Confirm that all diagnosis reading results are as shown in the table.
Are all diagnosis reading results as shown in the table?
Repair the wiring harness between joint connector (CAN3) C-24 and the ASC-ECU connector A-03.
Check the ASC-ECU connector A-03, and repair if necessary. If the ASC-ECU connector A-03 is in good condition, go to Step 9.
 
STEP 9. Scan tool MB991958 CAN bus diagnostics (retest the system)
Diagnose CAN-C (Main) bus line, and check if scan tool MB991958 screen shows normal state.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
Check the ASC-ECU connector A-03, and repair if necessary. If the ASC-ECU connector A-03 is in good condition, replace the ASC-ECU.
 
STEP 10. Check the CAN-C (Main) bus line between joint connector (CAN3) C-24 and the EPS-ECU connector C-144. Resistance measurement at joint connector (CAN3) C-24.
caution
  • A digital multimeter should be used. For details refer to .
  • The test wiring harness should be used. For details refer to .
  • When measuring the resistance, disconnect the negative battery terminal. For details refer to .
(1) Disconnect joint connector (CAN3) C-24, and measure at the wiring harness side.
(2) Ensure that the negative battery terminal is disconnected.
(3) Resistance between joint connector (CAN3) C-24 terminal No.9 (CAN_H) and body ground
OK: 1 kΩ or more
(4) Resistance between joint connector (CAN3) C-24 terminal No.20 (CAN_L) and body ground
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Repair the wiring harness between joint connector (CAN3) C-24 and intermediate connector C-128.
<Less than 1 kΩ> Go to Step 11.
 
STEP 11. Scan tool MB991958 CAN bus diagnostics [EPS-ECU connector C-144 disconnected]
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
(1) Disconnect EPS-ECU connector C-144 and read all diagnosis with scan tool MB991958.
(2) Confirm that all diagnosis reading results are as shown in the table.
Are all diagnosis reading results as shown in the table?
Check the intermediate connector C-146, and repair if necessary. If the intermediate connector C-146 is in good condition, repair the wiring harness between joint connector (CAN3) C-24 and the EPS-ECU connector C-144.
Check the EPS-ECU connector C-144, and repair if necessary. If the EPS-ECU connector C-144 is in good condition, go to Step 12.
 
STEP 12. Scan tool MB991958 CAN bus diagnostics (retest the system)
Diagnose CAN-C (Main) bus line, and check if scan tool MB991958 screen shows normal state.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
Check the EPS-ECU connector C-144, and repair if necessary. If the EPS-ECU connector C-144 is in good condition, replace the EPS-ECU.
 
STEP 13. Check the CAN-C (Main) bus line between joint connector (CAN2) C-202 and the ETACS-ECU connector C-411. Resistance measurement at joint connector (CAN2) C-202.
caution
  • A digital multimeter should be used. For details refer to .
  • The test wiring harness should be used. For details refer to .
  • When measuring the resistance, disconnect the negative battery terminal. For details refer to .
  • Strictly observe the specified wiring harness repair procedure. For details refer to .
(1) Disconnect joint connector (CAN2) C-202, and measure at the wiring harness side.
(2) Ensure that the negative battery terminal is disconnected.
(3) Resistance between joint connector (CAN2) C-202 terminal No.11 (CAN_H) and body ground
OK: 1 kΩ or more
(4) Resistance between joint connector (CAN2) C-202 terminal No.22 (CAN_L) and body ground
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Go to Step 14.
<Less than 1 kΩ> Repair the wiring harness between joint connector (CAN2) C-202 and the ETACS-ECU connector C-411.
 
STEP 14. Check the CAN-C (Main) bus line between joint connector (CAN2) C-202 and the column switch connector C-310. Resistance measurement at joint connector (CAN2) C-202.
caution
  • A digital multimeter should be used. For details refer to .
  • The test wiring harness should be used. For details refer to .
  • When measuring the resistance, disconnect the negative battery terminal. For details refer to .
(1) Disconnect joint connector (CAN2) C-202, and measure at the wiring harness side.
(2) Ensure that the negative battery terminal is disconnected.
(3) Resistance between joint connector (CAN2) C-202 terminal No.9 (CAN_H) and body ground
OK: 1 kΩ or more
(4) Resistance between joint connector (CAN2) C-202 terminal No.20 (CAN_L) and body ground
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Go to Step 17.
<Less than 1 kΩ> Go to Step 15.
 
STEP 15. Scan tool MB991958 CAN bus diagnostics [column switch connector C-310 disconnected]
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
(1) Disconnect column switch connector C-310 and read all diagnosis with scan tool MB991958.
(2) Confirm that all diagnosis reading results are as shown in the table.
Are all diagnosis reading results as shown in the table?
Repair the wiring harness between joint connector (CAN2) C-202 and the column switch connector C-310.
Check the column switch connector C-310, and repair if necessary. If the column switch connector C-310 is in good condition, go to Step 16.
 
STEP 16. Scan tool MB991958 CAN bus diagnostics (retest the system)
Diagnose CAN-C (Main) bus line, and check if scan tool MB991958 screen shows normal state.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
Check the column switch connector C-310, and repair if necessary. If the column switch connector C-310 is in good condition, replace the column switch.
 
STEP 17. Check the CAN-C (Main) bus line between joint connector (CAN2) C-202 and the AWD-ECU connector C-228. Resistance measurement at joint connector (CAN2) C-202.
noteStep 17, 18 and 19 are only for AWD. On vehicles without it, go to Step 20.
caution
  • A digital multimeter should be used. For details refer to .
  • The test wiring harness should be used. For details refer to .
  • When measuring the resistance, disconnect the negative battery terminal. For details refer to .
(1) Disconnect joint connector (CAN2) C-202, and measure at the wiring harness side.
(2) Ensure that the negative battery terminal is disconnected.
(3) Resistance between joint connector (CAN2) C-202 terminal No.8 (CAN_H) and body ground
OK: 1 kΩ or more
(4) Resistance between joint connector (CAN2) C-202 terminal No.19 (CAN_L) and body ground
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Go to Step 20.
<Less than 1 kΩ> Go to Step 18.
 
STEP 18. Scan tool MB991958 CAN bus diagnostics [AWD-ECU connector C-228 disconnected]
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
(1) Disconnect AWD-ECU connector C-228 and read all diagnosis with scan tool MB991958.
(2) Confirm that all diagnosis reading results are as shown in the table.
Are all diagnosis reading results as shown in the table?
Check the intermediate connector C-27, and repair if necessary. If the intermediate connector C-27 is in good condition, repair the wiring harness between joint connector (CAN2) C-202 and the AWD-ECU connector C-228.
Check the AWD-ECU connector C-228, and repair if necessary. If the AWD-ECU connector C-228 is in good condition, go to Step 19.
 
STEP 19. Scan tool MB991958 CAN bus diagnostics (retest the system)
Diagnose CAN-C (Main) bus line, and check if scan tool MB991958 screen shows normal state.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
Check the AWD-ECU connector C-228, and repair if necessary. If the AWD-ECU connector C-228 is in good condition, replace the AWD-ECU.
 
STEP 20. Check the CAN-C (Main) bus line between joint connector (CAN2) C-202 and the occupant classification-ECU connector D-48-2. Resistance measurement at joint connector (CAN2) C-202.
caution
  • A digital multimeter should be used. For details refer to .
  • The test wiring harness should be used. For details refer to .
  • When measuring the resistance, disconnect the negative battery terminal. For details refer to .
(1) Disconnect joint connector (CAN2) C-202, and measure at the wiring harness side.
(2) Ensure that the negative battery terminal is disconnected.
(3) Resistance between joint connector (CAN2) C-202 terminal No.2 (CAN_H) and body ground
OK: 1 kΩ or more
(4) Resistance between joint connector (CAN2) C-202 terminal No.13 (CAN_L) and body ground
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Go to Step 23.
<Less than 1 kΩ> Go to Step 21.
 
STEP 21. Scan tool MB991958 CAN bus diagnostics [occupant classification-ECU connector D-48-2 disconnected]
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
(1) Disconnect occupant classification-ECU connector D-48-2 and read all diagnosis with scan tool MB991958.
(2) Confirm that all diagnosis reading results are as shown in the table.
Are all diagnosis reading results as shown in the table?
Check the intermediate connectors C-17 and D-48, and repair if necessary. If the intermediate connectors C-27 and D-48 are in good condition, repair the wiring harness between joint connector (CAN2) C-202 and the occupant classification-ECU connector D-48-2.
Check the occupant classification-ECU connector D-48-2, and repair if necessary. If the occupant classification-ECU connector D-48-2 is in good condition, go to Step 22.
 
STEP 22. Scan tool MB991958 CAN bus diagnostics (retest the system)
Diagnose CAN-C (Main) bus line, and check if scan tool MB991958 screen shows normal state.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
Check the occupant classification-ECU connector D-48-2, and repair if necessary. If the occupant classification-ECU connector D-48-2 is in good condition, replace the occupant classification-ECU.
 
STEP 23. Check the CAN-C (Main) bus line between joint connector (CAN2) C-202 and the FCM/LDW/AHB-ECU connector E-18. Resistance measurement at joint connector (CAN2) C-202.
noteStep 23, 24 and 25 are only for vehicles with FCM. On vehicles without it, go to Step 26.
caution
  • A digital multimeter should be used. For details refer to .
  • The test wiring harness should be used. For details refer to .
  • When measuring the resistance, disconnect the negative battery terminal. For details refer to .
(1) Disconnect joint connector (CAN2) C-202, and measure at the wiring harness side.
(2) Ensure that the negative battery terminal is disconnected.
(3) Resistance between joint connector (CAN2) C-202 terminal No.5 (CAN_H) and body ground
OK: 1 kΩ or more
(4) Resistance between joint connector (CAN2) C-202 terminal No.16 (CAN_L) and body ground
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Go to Step 26.
<Less than 1 kΩ> Go to Step 24.
 
STEP 24. Scan tool MB991958 CAN bus diagnostics [FCM/LDW/AHB-ECU connector E-18 disconnected]
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
(1) Disconnect FCM/LDW/AHB-ECU connector E-18 and read all diagnosis with scan tool MB991958.
(2) Confirm that all diagnosis reading results are as shown in the table.
Are all diagnosis reading results as shown in the table?
Check the intermediate connector C-226, and repair if necessary. If the intermediate connector C-226 is in good condition, repair the wiring harness between joint connector (CAN2) C-202 and the FCM/LDW/AHB-ECU connector E-18.
Check the FCM/LDW/AHB-ECU connector E-18, and repair if necessary. If the FCM/LDW/AHB-ECU connector E-18 is in good condition, go to Step 25.
 
STEP 25. Scan tool MB991958 CAN bus diagnostics (retest the system)
Diagnose CAN-C (Main) bus line, and check if scan tool MB991958 screen shows normal state.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
Check the FCM/LDW/AHB-ECU connector E-18, and repair if necessary. If the FCM/LDW/AHB-ECU connector E-18 is in good condition, replace the FCM/LDW/AHB-ECU.
 
STEP 26. Check the CAN-C (Main) bus line between joint connector (CAN2) C-202 and the SRS-ECU connector C-126. Resistance measurement at joint connector (CAN2) C-202.
caution
  • A digital multimeter should be used. For details refer to .
  • The test wiring harness should be used. For details refer to .
  • When measuring the resistance, disconnect the negative battery terminal. For details refer to .
  • Strictly observe the specified wiring harness repair procedure. For details refer to .
(1) Disconnect joint connector (CAN2) C-202, and measure at the wiring harness side.
(2) Ensure that the negative battery terminal is disconnected.
(3) Resistance between joint connector (CAN2) C-202 terminal No.3 (CAN_H) and body ground
OK: 1 kΩ or more
(4) Resistance between joint connector (CAN2) C-202 terminal No.14 (CAN_L) and body ground
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Go to Step 29.
<Less than 1 kΩ> Go to Step 27.
 
STEP 27. Scan tool MB991958 CAN bus diagnostics [SRS-ECU connector C-126 disconnected]
cautionStrictly observe the specified wiring harness repair procedure. For details refer to .
(1) Disconnect SRS-ECU connector C-126 and read all diagnosis with scan tool MB991958.
(2) Confirm that all diagnosis reading results are as shown in the table.
Are all diagnosis reading results as shown in the table?
Repair the wiring harness between joint connector (CAN2) C-202 and the SRS-ECU connector C-126.
Check the SRS-ECU connector C-126, and repair if necessary. If the SRS-ECU connector C-126 is in good condition, go to Step 28.
 
STEP 28. Scan tool MB991958 CAN bus diagnostics (retest the system)
Diagnose CAN-C (Main) bus line, and check if scan tool MB991958 screen shows normal state.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
Check the SRS-ECU connector C-126, and repair if necessary. If the SRS-ECU connector C-126 is in good condition, replace the SRS-ECU.
 
STEP 29. Check the CAN-C (Main) bus line between joint connector (CAN2) C-202 and the gateway-ECU connector C-49. Resistance measurement at joint connector (CAN2) C-202.
caution
  • A digital multimeter should be used. For details refer to .
  • The test wiring harness should be used. For details refer to .
  • When measuring the resistance, disconnect the negative battery terminal. For details refer to .
  • Strictly observe the specified wiring harness repair procedure. For details refer to .
(1) Disconnect joint connector (CAN2) C-202, and measure at the wiring harness side.
(2) Ensure that the negative battery terminal is disconnected.
(3) Resistance between joint connector (CAN2) C-202 terminal No.4 (CAN_H) and body ground
OK: 1 kΩ or more
(4) Resistance between joint connector (CAN2) C-202 terminal No.15 (CAN_L) and body ground
OK: 1 kΩ or more
Is the check result normal?
<1 kΩ or more> Repair the wiring harness between joint connector (CAN2) C-202 and intermediate connector C-128.
<Less than 1 kΩ> Repair the wiring harness between joint connector (CAN2) C-202 and the gateway-ECU connector C-49.
 
STEP 30. Scan tool MB991958 CAN bus diagnostics [ETACS-ECU connector C-411 disconnected]
(1) Disconnect ETACS-ECU connector C-411 and read all diagnosis with scan tool MB991958.
(2) Confirm that all diagnosis reading results are as shown in the table.
Are all diagnosis reading results as shown in the table?
Go to Step 32.
Check the ETACS-ECU connector C-411, and repair if necessary. If the ETACS-ECU connector C-411 is in good condition, go to Step 31.
 
STEP 31. Scan tool MB991958 CAN bus diagnostics (retest the system)
Diagnose CAN-C (Main) bus line, and check if scan tool MB991958 screen shows normal state.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
Check the ETACS-ECU connector C-411, and repair if necessary. If the ETACS-ECU connector C-411 is in good condition, replace the ETACS-ECU.
 
STEP 32. Scan tool MB991958 CAN bus diagnostics [ECM connector B-27 disconnected]
(1) Disconnect ECM connector B-27 and read all diagnosis with scan tool MB991958.
(2) Confirm that all diagnosis reading results are as shown in the table.
Are all diagnosis reading results as shown in the table?
Check the gateway-ECU connector C-49, and repair if necessary. If the gateway-ECU connector C-49 is in good condition, go to Step 34.
Check the ECM connector B-27, and repair if necessary. If the ECM connector B-27 is in good condition, go to Step 33.
 
STEP 33. Scan tool MB991958 CAN bus diagnostics (retest the system)
Diagnose CAN-C (Main) bus line, and check if scan tool MB991958 screen shows normal state.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
Check the ECM connector B-27, and repair if necessary. If the ECM connector B-27 is in good condition, replace the ECM.
 
STEP 34. Scan tool MB991958 CAN bus diagnostics (retest the system)
Diagnose CAN-C (Main) bus line, and check if scan tool MB991958 screen shows normal state.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
Check the gateway-ECU connector C-49, and repair if necessary. If the gateway-ECU connector C-49 is in good condition, replace the gateway-ECU.