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Inspection Procedure A-1: Check the battery power supply circuit to the ETACS-ECU.
 
 
cautionWhenever the ECU is replaced, ensure that the power supply circuit, the ground circuit and the communication circuit are normal.
 
 
TECHNICAL DESCRIPTION (COMMENT)
If the ETACS-ECU functions do not work at all, the ETACS-ECU power supply system, ground system, or ETACS-ECU may have a problem.
 
 
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
  • MB992006: Extra Fine Probe
STEP 1. Resistance measurement at ETACS-ECU connector (EARTH, SGND terminal).
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Measure the resistance between the ETACS-ECU connector (EARTH terminal) and ground.
OK: The resistance should be 2 ohm or less.
(3) Measure the resistance between the ETACS-ECU connector (SGND terminal) and ground.
OK: The resistance should be 2 ohm or less.
Is the check result normal?
Go to Step 3.
Go to Step 2.
 
STEP 2. Check of open circuit in EARTH, SGND line between ETACS-ECU connector and ground.
Is the check result normal?
Intermittent malfunction is suspected (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Repair the connector(s) or wiring harness.
 
STEP 3. Voltage measurement at ETACS-ECU connector (ETACS +B terminal).
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Check the voltage between the ETACS-ECU connector (ETACS +B terminal) and ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage).
Is the check result normal?
Go to Step 5.
Go to Step 4.
 
STEP 4. Check of short to power supply, short to ground, and open circuit in ETACS +B line between fusible link and ETACS-ECU connector.
Is the check result normal?
Intermittent malfunction is suspected (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Repair the connector(s) or wiring harness.
 
STEP 5. Retest the system.
Check that the ETACS-ECU functions work normally.
Is the check result satisfactory?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Replace the ETACS-ECU.