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Inspection Procedure 1: The ignition switch (ACC) signal is not received.
 
 
caution
  • Before replacing the ECU, ensure that the power supply circuit, the ground circuit and the communication circuit are normal.
  • When the ETACS-ECU of vehicles without KOS is replaced, the encrypted code of the ignition key needs to be registered to the ETACS-ECU. (If the encrypted code is not registered, the engine cannot be started. Register the encrypted code as described in Immobilizer System - How to Register Key ID .)
 
 
TECHNICAL DESCRIPTION (COMMENT)
If there is an error to the input signal (ACC) from the ignition switch <Vehicles without KOS> or OSS-ECU <Vehicles with one touch start system>, or if the ACC relay in ETACS-ECU does not function normally, the ignition switch (ACC) signal is no longer output to the communication line.
 
 
TROUBLESHOOTING HINTS
  • The ETACS-ECU may be defective
  • The ignition switch may be defective <Vehicles without KOS>
  • The OSS-ECU may be defective <Vehicles with one touch start system>
  • 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. Voltage measurement at ETACS-ECU connector (ACC terminal).
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Turn the ignition switch to the "ACC" position.
(3) Check the voltage between the ETACS-ECU connector (ACC 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 2.
: Go to Step 3.
 
STEP 2. Using scan tool (M.U.T.-III), read the OSS diagnostic trouble code.
(1)
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).
Connect scan tool (M.U.T.-III). Refer to "How to connect the Scan Tool (M.U.T.-III) ."
(2) Turn the ignition switch to the "ON" position.
(3) Check whether the OSS-ECU sets a DTC.
Is the DTC set?
Diagnose the OSS-ECU. Refer to GROUP 42B, Troubleshooting .
Go to Step 4.
 
STEP 3. Ignition switch check.
Check the ignition switch. Refer to .
Is the check result normal?
Go to Step 4.
Troubleshoot the ignition switch. Refer to Inspection Procedure 2 "Malfunction of the ignition switch power supply system" .
 
STEP 4. Check of short to power supply, short to ground, and open circuit in ACC line between ignition switch (ACC) <Vehicles without KOS> or OSS-ECU (ACC) <Vehicles with one touch start system> and ETACS-ECU connector.
Is the check result normal?
Go to Step 5.
Repair the connector(s) or wiring harness.
 
STEP 5. Using scan tool (M.U.T.-III), check data list.
Check the input signals from the ignition switch (ACC).
  • Turn the ignition switch to the ACC position.
 
Item No.Item nameNormal condition
288ACC switchON
Item No.Item nameNormal condition
288ACC switchON
OK: Normal condition is displayed.
Is the check result normal?
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.