Vehicles With Keyless Entry System
Tone Alarm: Seat Belt Tone Alarm Function does not Work Normally.Seat Belt Tone Alarm Function:
NOTE: This troubleshooting procedure requires the use of scan tool MB991958 and SWS monitor kit MB991813. For details on how to use the SWS monitor, refer to "How to use SWS monitor." How To Use SWS Monitor
CIRCUIT OPERATION
The ETACS-ECU operates the seat belt tone alarm function according to signals from the following switches:
- Ignition switch (IG1): ON
- Driver's seat belt switch: ON
- Vehicle speed signal: 8 km/h (5 mph) or more
The ETACS-ECU operates the seat belt tone alarm function under the following conditions:
- Ignition switch (IG1): "ON" position
- Driver's seat belt: Unfastened
- Vehicle speed: 8 km/h (5 mph) or more
TECHNICAL DESCRIPTION (COMMENT)
If the function does not work normally, the input circuit system from the switches or the ETACS-ECU may be defective (refer to "CIRCUIT OPERATION").
TROUBLESHOOTING HINTS
- The driver's seat belt switch 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:
- MB991223: Harness Set
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: Vehicles communication interface (V.C.I.)
- MB991827: MUT-III USB cable
- MB991911: MUT-III Main harness B
- MB991813: SWS monitor kit
- MB991806: SWS monitor cartridge
- MB991812: SWS monitor harness (for column-ECU)
- MB991922: Probe harness
STEP 1. Use scan tool MB991958 to select "ECU COMM CHK" on the SWS monitor display.
Check the ETACS-ECU.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958. Connect special tool MB991910 before connecting special tool MB991812. Be sure to connect special tool MB991806 after turning on special tool MB991824.
1. Connect the special tool. Refer to "How to connect SWS monitor." How to Connect SWS Monitor
2. When the ignition switch is turned to the "ON" position.
3. Operate scan tool MB991958 according to the procedure below to display "ECU COMM Check."
a. Select "Interactive Diagnosis."
b. Select "System Select."
c. Select "SWS."
d. Select "SWS MONITOR."
e. Select "ECU COMM Check."
4. Scan tool MB991958 should show "OK" on the "ECU COMM Check" menu for the "ETACS ECU" menu.
Q: Is "OK" displayed on the "ETACS ECU" menu?
YES: Go to Step 2.
NO: Refer to Inspection Procedure A-3 "Communication with ETACS-ECU is not possible."
STEP 2. Check the input signal by using "DATA LIST" menu of the SWS monitor.
Turn the ignition switch to the "ON" position before checking input signals from the ignition switch (IG1).
1. Operate scan tool MB991958 according to the procedure below to display "ETACS ECU."
a. Select "Interactive Diagnosis."
b. Select "System Select."
c. Select "SWS."
d. Select "SWS MONITOR."
e. Select "Data List."
f. Select "ETACS ECU."
2. Check that normal conditions are displayed for the items described in the table.
Q: Does scan tool MB991958 display "IG SW (IG1)" as normal condition?
YES: Go to Step 3.
NO: Refer to Inspection Procedure O-2 "ETACS-ECU does not receive a signal from the ignition switch (IG1)."
STEP 3. Check the input signal (by using the Pulse check mode of the monitor).
1. Operate scan tool MB991958 according to the procedure below to display "Pulse check."
a. Select "Interactive Diagnosis."
b. Select "System Select."
c. Select "SWS."
d. Select "Pulse Checking."
2. When the driver's seat belt is unfastened, check if scan tool MB991958 sounds or not.
Q: Does scan tool MB991958 sound when the driver's side seat belt is unfastened?
YES: Go to Step 4.
NO: Refer to Inspection Procedure P-3 "ETACS-ECU does not receive a signal from the driver's side seat belt switch."
STEP 4. Check the input signal (by using the Pulse check mode of the monitor).
Check the input signals from the vehicle speed sensor.
1. Operate scan tool MB991958 according to the procedure below to display "Pulse check."
a. Select "Interactive Diagnosis."
b. Select "System Select."
c. Select "SWS."
d. Select "Pulse Checking."
2. When the vehicle speed exceeds 10 km/h (6.2 mph), check that scan tool MB991958 sounds or not.
Q: Does scan tool MB991958 sound when the vehicle speed exceeds 10 km/h (6.2 mph)?
YES: Replace the ETACS-ECU. Check that the seat belt tone alarm function works normally.
NO: Refer to Inspection Procedure P-11 "ETACS-ECU does not receive a signal from the vehicle speed sensor."