Input Signal Procedures

INPUT SIGNAL PROCEDURES

Signals from transmitter switches are not received.

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

COMMENTS ON TROUBLE SYMPTOM
Input signal from the keyless entry transmitter is used to operate the keyless entry system. If the signal is abnormal, the key-less entry system will not work normally.

PROBABLE CAUSES
- Battery discharged in the transmitter
- Malfunction of the transmitter
- Malfunction of WCM

DIAGNOSTIC PROCEDURE

Required Special Tools:
- MB992006: Extra fine probe
- MB991223: Harness set
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)

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

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.






1. Connect scan tool MB991958. Refer to "How to connect scan tool (M.U.T.-III)." How to Connect the Scan Tool (M.U.T.-III)
2. Turn the ignition switch to the "ON" position.
3. Check whether the WCM related DTC is set.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the DTC set?

YES : Diagnose the WCM. How to Connect the Scan Tool (M.U.T.-III)

NO : Go to Step 2.

STEP 2. Check the transmitter battery.






Measure the voltage of the transmitter battery.
- The value should be approximately 2.5 - 3.2 volts.

Q: Is the measured voltage approximately 2.5 - 3.2 volts?

YES : Go to Step 3.

NO : Replace the battery. If the transmitter can be registered normally, and operates normally, it indicates that the transmitter is sending normal signal to the WCM.

STEP 3. Register the keyless entry secret code using a known-normal transmitter of the same type again, and check the trouble symptom.
1. Register a known-good transmitter of the same type.
2. Check if the signals from the transmitter switches are received.

Q: Can the transmitter be registered correctly?

YES : Replace the original transmitter with a new one.

NO : Replace the WCM.(Including when the new transmitter cannot be registered). Replace WCM and register the ID codes. If the transmitter works normally, the input signal from the transmitter should be normal. ID Codes Registration Procedure