Inspection Procedure O-4
ETACS-ECU does not Receive "R" Position Signal from the Backup Light SwitchBuckup Light Switch Input Circuit Part 1:
Buckup Light Switch Input Circuit Part 2:
CIRCUIT OPERATION
The ETACS-ECU operates the rear wiper according to signal from the backup light switch.
TECHNICAL DESCRIPTION (COMMENT)
If the signal is not normal, the rear wiper does not operate consecutively twice when the shift lever is moved to the "R" position with the rear wiper on. If the signal is not normal, the backup light switch or the ETACS-ECU may be defective.
TROUBLESHOOTING HINTS
- Malfunction of the backup light switch
- Malfunction of the ETACS-ECU
- Damaged harness wires or connectors
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: Vehicles communication interface
- MB991827: MUT-III USB cable
- MB991911: MUT-III Main harness B
STEP 1. Check the backup light switch.
Disconnect backup light switch connector B-37. Then check continuity between the switch terminals.
Q: Is the backup light switch in good condition?
YES: Go to Step 2.
NO: Replace the backup light switch. If the rear wiper operates normally, it indicates that a correct "R" position signal is sent from the backup light switch.
STEP 2. Check at backup light switch connector B-37 in order to check the ignition switch (IG1) line of the power supply to the backup light switch.
1. Disconnect backup light switch connector B-37, and measure at the wiring harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 1 and ground.
- The measured value should be approximately 12 volts (battery positive voltage).
Q: Does the measured voltage correspond with this range?
YES: Go to Step 5.
NO: Go to Step 3.
STEP 3. Check backup light switch connector B-37 for damage.
Q: Is the backup light switch connector B-37 in good condition?
YES: Go to Step 4.
NO: Repair or replace the connector. Refer to Harness Connector Inspection. If the rear wiper operates normally, it indicates that a correct "R" position signal is sent from the backup light switch.
STEP 4. Check the wiring harness between backup light switch connector B-37 (terminal 1) and the ignition switch (IG1).
NOTE: Also check junction block connectors C-111, C-112 and intermediate connector C-28. If junction block connectors C-111, C-112 or intermediate connectors C-28 is damaged, repair or replace the connector as described in Harness Connector Inspection.
Q: Is the wiring harness between backup light switch connector B-37 (terminal 1) and the ignition switch (IG1) in good condition?
YES: No action to be taken.
NO: Repair the wiring harness. If the rear wiper operates normally, it indicates that a correct "R" position signal is sent from the backup light switch.
STEP 5. Check backup light switch connector B-37 and ETACS-ECU connector C-117 for damage.
Q: Are backup light switch connector B-37 and ETACS-ECU connector C-117 in good condition?
YES: Go to Step 6.
NO: Repair or replace the connector. Refer to Harness Connector Inspection. If the rear wiper operates normally, it indicates that a correct "R" position signal is sent from the backup light switch.
STEP 6. Check the wiring harness between backup light switch connector B-37 (terminal 2) and ETACS-ECU connector C-117 (terminal 39).
NOTE: Also check intermediate connector C-28. If intermediate connectors C-28 is damaged, repair or replace the connector as described in Harness Connector Inspection.
Q: Is the wiring harness between backup light switch connector B-37 (terminal 2) and ETACS-ECU connector C-117 (terminal 39) in good condition?
YES: Replace the ETACS-ECU. If the rear wiper operates normally, it indicates that a correct "R" position signal is sent from the backup light switch.
NO: Repair the wiring harness. If the rear wiper operates normally, it indicates that a correct "R" position signal is sent from the backup light switch.