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Malfunction of the ignition switch power supply system
 
 
cautionWhenever the ECU is replaced, ensure that the input and output signal circuits are normal.
 
 
TECHNICAL DESCRIPTION (COMMENT)
When the power supply system of ignition switch has a problem, none of the equipment and system connected to the ignition switch works even if the ignition switch is operated.
 
 
TROUBLESHOOTING HINTS
  • The ignition switch may be defective
  • The fuse may be defective
  • 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:
  • MB992006: Extra fine probe
  • MB991223: Harness set
STEP 1. Check the battery power supply circuit to the ignition switch. Measure the voltage at ignition switch connector.
(1) Disconnect the ignition switch connector and measure the voltage at ignition switch connector wiring harness side.
(2) Check the voltage between the ignition switch connector (power supply terminal) and ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage).
Is the measured voltage approximately 12 volts (battery positive voltage)?
Go to Step 4.
Go to Step 2.
 
STEP 2. Check the fuse.
Is the check result normal?
Go to Step 3.
Replace the fuse. (Check that there is not a short to ground in the circuit of lower reaches before replacing. If there are any problems, replace the fuse after the circuit of lower reaches is repaired.)
 
STEP 3. Check of open circuit in power supply line between ignition switch connector and junction block connector
Is the check result normal?
Go to Step 5.
Repair the connector(s) or wiring harness.
 
STEP 4. Check the ignition switch.
Refer to .
Is the ignition switch in good condition?
Go to Step 5.
Replace the ignition switch.
 
STEP 5. Retest the system.
When the ignition switch is operated, do the equipment and system work normally?
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.