Inspection Procedure 1
Communication With Scan Tool MB991502 Is Not Possible (Communication With The Auto-cruise Control-ECU Only Is Not Possible.)Auto-Cruise Control-ECU Supply, Ground And Data Link Circuit Part 1:
Auto-Cruise Control-ECU Supply, Ground And Data Link Circuit Part 2:
CIRCUIT OPERATION
Power of the auto-cruise control-ECU is transmitted from the ignition switch (IG1) to the auto-cruise control-ECU through junction block fuse 17 in the junction block.
TECHNICAL DESCRIPTION (COMMENT)
The cause is probably a malfunction of the auto-cruise control-ECU power supply circuit or the auto-cruise control-ECU ground circuit.
TROUBLESHOOTING HINTS
- Damaged harness or connector.
- Malfunction of the auto-cruise control-ECU.
DIAGNOSIS
Required Special Tool:
- MB991223: Harness Set
STEP 1. Measure the signal voltage at auto-cruise control-ECU connector C-52 by backprobing.
1. Do not disconnect auto-cruise control-ECU connector C-52.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between auto-cruise control-ECU connector C-52 terminal 6 and ground by backprobing.
- The voltage should measure battery positive voltage.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage battery positive voltage?
YES: Go to Step 4.
NO: Go to Step 2.
STEP 2. Check auto-cruise control-ECU connector C-52 and Junction block connector C-84 and C-87 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 or replace the faulty connector. Go to Step 9.
STEP 3. Check the harness wire between ignition switch and auto-cruise control-ECU connector C-52 terminal 6 for damage.
Q: Is the harness wire in good condition?
YES: It can be assumed that this malfunction is intermittent. Go to Step 9.
NO: Repair the damaged harness wire. Go to Step 9.
STEP 4. Measure the ground circuit voltage at auto-cruise control-ECU connector C-52 by backprobing.
1. Do not disconnect auto-cruise control-ECU connector C-52.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between auto-cruise control-ECU connector C-52 terminal 14 and ground by backprobing.
- The voltage should measure 0.5 volt or less.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage 0.5 volts or less?
YES: Go to Step 7.
NO: Go to Step 5.
STEP 5. Check auto-cruise control-ECU connector C-52 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Is the connector and terminals in good condition?
YES: Go to Step 6.
NO: Repair or replace the faulty connector. Go to Step 9.
STEP 6. Check the harness wire between auto-cruise control-ECU connector C-52 terminal 14 and ground for damage.
Q: Is the harness wire in good condition?
YES: It can be assumed that this malfunction is intermittent. Go to Step 9.
NO: Repair the damaged harness wire. Go to Step 9.
STEP 7. Check data link connector C-23 and auto-cruise control-ECU connector C-52 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 or replace the faulty connector. Go to Step 9.
STEP 8. Check the harness wire between data link connector C-23 terminal 13 and auto-cruise control-ECU connector C-52 terminal 11 for damage.
Q: Is the harness wire in good condition?
YES: Check that the malfunction is eliminated. If the malfunction is eliminated, it can be assumed that this malfunction is intermittent. If the malfunction is not eliminated, replace the auto-cruise control-ECU, and then go to Step 9.
NO: Repair the damaged harness wire. Go to Step 9.
STEP 9. Check that the malfunction is eliminated
Q: Is the malfunction eliminated?
YES: This procedure is complete.
NO: Go to Step 1.