[Previous][Next]
Inspection Procedure 3: Abnormality in KOS-ECU power supply and ground circuits.
 
 
cautionBefore replacing the ECU, ensure that the power supply circuit, the ground circuit and the communication circuit are normal.
 
 
TECHNICAL DESCRIPTION (COMMENT)
If the KOS-ECU does not work at all or if the KOS-ECU cannot communicate with the scan tool, the KOS-ECU power supply or the ground circuit may be defective.
 
 
TROUBLESHOOTING HINTS
  • Damaged wiring harness and connectors
  • Malfunction of KOS-ECU
 
 
DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
STEP 1. Resistance measurement at KOS-ECU connector (GND line)
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Measure the resistance between the KOS-ECU connector (GND line) and body ground.
OK: Continuity exists (2 Ω or less)
Is the check result normal?
Go to Step 3.
Go to Step 2.
 
STEP 2. Check of open circuit in GND line between KOS-ECU connector and body 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 KOS-ECU connector (IG1 line)
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Check the voltage between the KOS-ECU connector (IG1 line) and body ground.
OK: System 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 IG1 line between ETACS-ECU connector and KOS-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. Voltage measurement at KOS-ECU connector (PWR line)
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Check the voltage between the KOS-ECU connector (PWR terminal) and body ground.
OK: System voltage
Is the check result normal?
Replace KOS-ECU and register the ID codes (Refer to ).
Go to Step 6.
 
STEP 6. Check of short to power supply, short to ground, and open circuit in PWR line between fusible link (6) and KOS-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.