Inspection Procedure 3

Inspection Procedure 3: The tachometer does not work (the other meters work).

TECHNICAL DESCRIPTION (COMMENT)

If only the tachometer does not operate, the ignition signal from the engine ECU may not be received or the combination meter may have a problem.

TROUBLESHOOTING HINTS

- The combination meter may be defective
- The engine control module may be defective

DIAGNOSIS

Required Special Tools:

- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicles 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, diagnose the CAN bus line.





(1)
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 scan tool MB991958. Refer to "How to connect the Scan Tool (M.U.T.-III) Reading and Clearing Diagnostic Trouble Codes."
(2)Turn the ignition switch to the "ON" position.
(3)Diagnose the CAN bus line.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the CAN bus line found to be normal?

YES Go to Step 2.

NO Repair the CAN bus line CAN Bus Diagnostics Chart).

STEP 2. Using scan tool MB991958, read the combination meter diagnostic trouble code.

Check if DTC is set to the combination meter.

Q. Is the DTC set?

YES Troubleshoot the combination meter (Refer to Combination Meter).
NO Go to Step 3.
STEP 3. Using scan tool MB991958, read the MFI diagnostic trouble code.

Check if DTC is set to the engine control module.

Q. Is the DTC set?

YES Troubleshoot the MFI Multiport Fuel Injection (MFI)).
NO Go to Step 4.
STEP 4. Using scan tool MB991958, check data list.

(1)Turn the ignition switch to the "ON" position.

(2)Check the data list on the combination meter.

- Item 87: Tachometer
- Should read engine speed.

(3)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Does it read engine speed?

YES Go to Step 5.
NO Troubleshoot the MFI Multiport Fuel Injection (MFI)).
Complete the engine troubleshooting, and then go to Step 6.
STEP 5. Using scan tool MB991958, check actuator test.

(1)Turn the ignition switch to the "ON" position.

(2)Conduct the actuator test of the combination meter.

- Item 2: Tachometer
- The tachometer operates up to the set position.

(3)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the check result normally?

YES Go to Step 6.
NO Replace the combination meter.
STEP 6. Retest the system

Check that the tachometer works normally.

Q. Is the check result normal?

YES The procedure is complete.
NO Go to Step 1.