Inspection Procedure A-3
Communication with the ETACS-ECU is not possible.ETACS-ECU Power Supply And SWS Communication Circuit Part 1:
ETACS-ECU Power Supply And SWS Communication Circuit Part 2:
CIRCUIT OPERATION
- The power supply to the ETACS-ECU is provided by the battery and the ignition switch (IG1).
- If the power supply system from the battery is defective, the system operates by the power supply from the ignition switch (IG1).
TECHNICAL DESCRIPTION (COMMENT)
It is suspected that the power supply circuit to the ETACS-ECU is defective, or the wiring harness between the SWS monitor kit and the ETACS-ECU or their connector(s) is damaged. If the battery power supply circuit to the ECU (terminal 20 of the ETACS-ECU) is damaged, also check the power supply circuit from the ignition switch (IG1) (terminal 8 of the ETACS-ECU), and repair if necessary. If the ground circuit to the ECU (terminal 3 of the ETACS-ECU) is damaged, also check the ground circuit to the sensor (terminal 56 of the ETACS-ECU), and repair if necessary.
TROUBLESHOOTING HINTS
- The ETACS-ECU may be defective
- The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector
DIAGNOSIS
Required Special Tools:
- MB991223: Harness Set
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: Vehicles communication interface (V.C.I.)
- MB991827: MUT-III USB cable
- MB991911: MUT-III Main harness B
- MB991813: SWS monitor kit
- MB991806: SWS monitor cartridge
- MB991812: SWS monitor harness (for column-ECU)
- MB991922: Probe harness
STEP 1. Check ETACS-ECU connector C-119 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Is ETACS-ECU connector C-119 in good condition?
YES: Go to Step 2.
NO: Repair or replace the damaged component(s). Refer to Harness Connector Inspection. The system should communicate with the ETACS-ECU normally.
STEP 2. Check the battery power supply circuit to the ETACS-ECU. Measure the voltage at ETACS-ECU connector C-119.
1. Disconnect ETACS-ECU connector C-119 and measure the voltage available at the junction block side of the connector.
2. Measure the voltage between terminal 20 and ground.
- The measured value should be approximately 12 volts (battery positive voltage).
Q: Is the measured voltage approximately 12 volts (battery positive voltage)?
YES: Go to Step 4.
NO: Go to Step 3.
STEP 3. Check the wiring harness between ETACS-ECU connector C-119 (terminal 20) and the battery.
NOTE: Also check intermediate connector C-89, junction block connector C-112 and joint connector C-78 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-89, junction block connector C-112 or joint connectors C-78 is damaged, repair or replace the damaged component(s) as described in Harness Connector Inspection.
Q: Is the wiring harness between ETACS-ECU connector C-119 (terminal 20) and the battery in good condition?
YES: No action is necessary and testing is complete.
NO: The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary. The system should communicate with the ETACS-ECU normally.
STEP 4. Check the ground circuit to the ETACS-ECU. Measure the resistance at ETACS-ECU connector C-119.
1. Disconnect ETACS-ECU connector C-119 and measure the resistance available at the junction block side of the connector.
2. Measure the resistance value between terminal 3 and ground.
- The resistance should equal 2 ohms or less.
Q: Is the measured resistance 2 ohms or less?
YES: Go to Step 7.
NO: Go to Step 5.
STEP 5. Check the wiring harness between ETACS-ECU connector C-119 (terminal 3) and the ground.
NOTE: Also check junction block connector C-108 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If junction block connector C-108 is damaged, repair or replace the damaged component(s) as described in Harness Connector Inspection.
Q: Is the wiring harness between ETACS-ECU connector C-119 (terminal 3) and the ground in good condition?
YES: No action to be taken.
NO: Repair the wiring harness. The system should communicate with the ETACS-ECU normally.
STEP 6. Check column switch connector C-86 and ETACS-ECU connector C-118 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Are column switch connector C-86 and ETACS-ECU connector C-118 in good condition?
YES: Go to Step 7.
NO: Repair or replace the damaged component(s). Refer to Harness Connector Inspection. The system should communicate with the ETACS-ECU normally.
STEP 7. Check the wiring harness between column switch connector C-86 (terminal 3) and ETACS-ECU connector C-118 (terminal 59).
NOTE: Also check joint connector C-78 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If joint connector C-78 is damaged, repair or replace the damaged component(s) as described in Harness Connector Inspection.
Q: Is the wiring harness between column switch connector C-86 (terminal 3) and ETACS-ECU connector C-118 (terminal 59) in good condition?
YES: Replace the ETACS-ECU. The system should communicate with the ETACS-ECU normally.
NO: The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary. The system should communicate with the ETACS-ECU normally.