A - Charts
Scan tool MB991502 communication is not possibleETACS-ECU Power Supply And Scan Tool Communication Circuit:
Connectors:
CIRCUIT OPERATION
The ETACS-ECU receives a diagnostic trouble code and switch signals from the data link connector.
TECHNICAL DESCRIPTION (COMMENT)
The harness wires between the ETACS-ECU power supply line or the ETACS-ECU and the data link connector may be defective.
TROUBLESHOOTING HINTS
- Malfunction of the ETACS-ECU
- Damaged harness wires or connectors
DIAGNOSIS
Required Special Tools:
- MB991223: Harness Set
STEP 1. Check the communication with other Systems.
Q: Can the scan tool communicate with no systems?
YES: Refer to Computers/Testing/Diagnosis By Symptom/Symptom Procedures/Inspection Procedure 1.
NO (can not communicate with SWS only): Go to Step 2.
STEP 2. Check the ignition switch positions.
Q: Can scan tool MB991502 communicate with the ETACS-ECU with the ignition switch at any position other than "ON"?
YES: Go to Step 3.
NO: Check the ETACS-ECU battery circuits. Refer to Inspection Procedure P-1.
STEP 3. Cheek data link connector C-29 and ETACS-ECU connector C-111 for damage.
Q: Are data link connector C-29 and ETACS-ECU connector C-111 in good condition?
YES: Go to Step 4.
NO: Repair or replace them. Refer to Harness Connector Inspection. Scan tool MB991502 should communicate with the SWS.
STEP 4. Check the harness wires between data link connector C-29 and ETACS-ECU connector C-111.
NOTE: After checking joint connector C-77, check the wires. If joint connector C-77 is damaged, repair or replace it. Refer to Harness Connector Inspection.
Q: Are the harness wires between data link connector C-29 and ETACS-ECU connector C-111 in good condition?
YES: Go to Step 5.
NO: Repair them. Scan tool MB991502 should communicate with the SWS.
STEP 5. Check the ETACS-ECU ground circuit at the ETACS-ECU connector C-114.
1. Disconnect the ETACS-ECU connector C-114 and measure at the junction block side.
2. Measure the resistance between terminal 1 and ground.
Q: Is the resistance less than 2 ohms?
YES: Replace the ETACS-ECU. Scan tool MB991502 should communicate with the SWS.
NO: Go to Step 6.
STEP 6. Check the ETACS-ECU connector C-114 for damage.
Q: Is ETACS-ECU connector C-114 in good condition?
YES: Go to Step 7.
NO: Repair or replace it. Refer to Harness Connector Inspection. Scan tool MB991502 should communicate with the SWS.
STEP 7. Check the harness wires between ETACS-ECU connector C-114 and ground.
NOTE: After checking junction block connector C-101, check the wires. If junction block connector C-101 is damaged, repair or replace it. Refer to Harness Connector Inspection.
Q: Are the harness wires between ETACS-ECU connector C-114 and ground in good condition?
YES: There is no action to be taken.
NO: Repair them. Scan tool MB991502 should communicate with the SWS.