Inspection Procedure A-3

Communication with the ETACS-ECU is Impossible.

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
- Malfunction of the ETACS-ECU
- Damaged harness wires or connectors

DIAGNOSIS

Required Special Tools:
- MB991223: Harness Set
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: Vehicles communication interface
- 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. Measure at ETACS-ECU connector C-119 in order to check the battery power supply circuit to the ETACS-ECU.




1. Disconnect ETACS-ECU connector C-119, and measure at the junction block side.




2. Measure the voltage between terminal 20 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 4.

NO: Go to Step 2.




STEP 2. Check ETACS-ECU connector C-119 for damage.

Q: Is ETACS-ECU connector C-119 in good condition?

YES: Go to Step 3.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. The system should communicate with the ETACS-ECU normally.













STEP 3. Check the wiring harness between ETACS-ECU connector C-119 (terminal 20) and the battery.

NOTE: Also check joint connector C-78, junction block connector C-112 and intermediate connector C-89. If joint connectors C-78, junction block connector C-112 or intermediate connector C-89 is damaged, repair or replace the connector 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 to be taken.

NO: Repair the wiring harness. The system should communicate with the ETACS-ECU normally.

STEP 4. Measure at ETACS-ECU connector C-119 in order to check the ground circuit to the ETACS-ECU.




1. Disconnect ETACS-ECU connector C-119, and measure at the junction block side.




2. Measure the resistance value between terminal 3 and ground.
- The measured value should be 2 ohm or less.

Q: Does the measured resistance value correspond with this range?

YES: Go to Step 7.

NO: Go to Step 5.




STEP 5. Check ETACS-ECU connector C-119 for damage.

Q: Is ETACS-ECU connector C-119 in good condition?

YES: Go to Step 6.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. The system should communicate with the ETACS-ECU normally.







STEP 6. Check the wiring harness between ETACS-ECU connector C-119 (terminal 3) and the ground.

NOTE: Also check junction block connector C-108. If junction block connector C-108 is damaged, repair or replace the connector 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 7. Check column switch connector C-86 and ETACS-ECU connector C-118 for damage.

Q: Are column switch connector C-86 and ETACS-ECU connector C-118 in good condition?

YES: Go to Step 8.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. The system should communicate with the ETACS-ECU normally.










STEP 8. 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. If joint connector C-78 is damaged, repair or replace the connector 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: Repair the wiring harness. The system should communicate with the ETACS-ECU normally.