Inspection Procedure 3

Inspection Procedure 3: Vehicle power does not turn ON. (Not possible with power supply mode ACC only)

CAUTION:
Before replacing the ECU, ensure that the power supply circuit, the ground circuit and the communication circuit are normal.

TECHNICAL DESCRIPTION (COMMENT)

When the vehicle power does not turn ON (not possible with power supply mode ACC only), the possible cause may be that the OSS-ECU cannot output the ACC signal, or that the ACC internal relay of ETACS-ECU does not turn ON. Therefore, OSS-ECU or ETACS-ECU may have a problem.

TROUBLESHOOTING HINTS

- Malfunction of OSS-ECU
- Malfunction of ETACS-ECU
- Damaged harness wires and connectors

DIAGNOSIS

STEP 1. Using scan tool MB991958, read the diagnostic trouble code

(1)
CAUTION:
To prevent damage to scan tool (MB991958), always turn the power supply mode of the engine switch to the OFF position before connecting or disconnecting scan tool (MB991958).

Connect scan tool MB991958. Refer to "How to connect scan tool (M.U.T.-III) Reading and Clearing Diagnostic Trouble Codes."

(2)After performing the forced power supply output (refer to forced power supply output procedure Programming and Relearning) "IG-ON".

(3)Check if the DTC is set to OSS-ECU.

(4)Turn the power supply mode of the engine switch to OFF.

Q. Is the DTC set?

YES Diagnose the OSS-ECU. Refer to diagnostic trouble code chart Keyless Operation System (KOS).

NO Go to Step 2.

STEP 2. Voltage measurement at ETACS-ECU connector (ACC terminal)

(1)With the ETACS-ECU connector kept connected, measure by backprobing.

(2)Using the scan tool MB991958, set the forced power supply output to "IG-ACC" (refer to forced power supply output procedure Programming and Relearning).

(3)Measure the voltage between the ETACS-ECU connector (ACC terminal) and body ground.
OK: Battery voltage


Q. Is the check result normal?

YES Go to Step 3.

NO Replace the OSS-ECU and register the VIN (Refer to Programming and Relearning).

STEP 3. Check of the troubles

Check that the vehicle power (power supply mode ACC) can be turned ON.

Q. Is the check result normal?

YES Intermittent malfunction is suspected How to Cope With Intermittent Malfunctions).

NO Carry out the troubleshooting relevant to the input signal of ETACS-ECU Symptom Chart).