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Inspection Procedure 1: Scan Tool (M.U.T.-IIISE) cannot communicate with electric parking brake system (the power supply to the electric parking brake ECU fails).
 
 
caution
  • If there is any problem in the CAN bus lines, an incorrect DTC may be set. Prior to this diagnosis, diagnose the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ).
  • Whenever ECU is replaced, ensure that the CAN bus lines are normal.
 
 
COMMENTS ON TROUBLE SYMPTOM
When Scan Tool (M.U.T.-IIISE) cannot communicate with the electric parking brake system, the CAN bus lines, electric parking brake ECU power supply circuit system, ground, or electric parking brake ECU may be faulty.
 
 
TROUBLESHOOTING HINTS
  • Open or ground fault in the electric parking brake ECU power supply circuit, or defective connector(s)
  • Malfunction of the electric parking brake ECU
 
 
DIAGNOSIS
Required Special Tools:
  • MB992006: Extra Fine Probe
STEP 1. Measure the resistance at the electric parking brake ECU connector.
(1) Disconnect the connector and measure at the wiring harness side.
(2) Measure the resistance between GND1 terminal and ground.
OK: The resistance should be 2 ohms or less
(3) Measure the resistance between GND2 terminal and ground.
OK: The resistance should be 2 ohms or less
Is the check result normal?
Go to Step 2.
The ground circuit may be open. Repair the wiring harness wires or connectors between the electric parking brake ECU connector and the ground.
 
STEP 2. Measure the voltage at the electric parking brake ECU connector.
(1) Disconnect the electric parking brake ECU connector.
(2) Measure the voltage between the +ECU terminal and ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage).
Is the check result normal?
Go to Step 3.
The power supply circuit may be open. Repair the wiring harness wires or connectors between the electric parking brake ECU connector and the fusible link.
 
STEP 3. Measure the voltage at the electric parking brake ECU connector.
(1) Disconnect the electric parking brake ECU connector and measure at the wiring harness side.
(2) Turn on the power supply mode of the electric motor switch.
(3) Measure the voltage between the IG1 terminal and ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage).
Is the check result normal?
Go to Step 4.
The IG1 signal circuit may be open or short to ground. Repair the wiring harness wires or connectors between the electric parking brake ECU connector and the ETACS-ECU (IG1 relay).
 
STEP 4. Retest the system.
Is the check result normal?
The trouble can be an intermittent malfunction (GROUP 00 - How to use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
Replace the electric parking brake ECU (Refer to ).