Tachometer Malfunction

METER: METER / GAUGE SYSTEM: Tachometer Malfunction
- Tachometer Malfunction

WIRING DIAGRAM





INSEPCTION PROCEDURE

PROCEDURE

1. PERFORM ACTIVE TEST USING TECHSTREAM (TACHOMETER)

(a) Select the Active Test, use the Techstream to generate a control command, and then check that the tachometer operates.

Combination meter





OK:

The tachometer operates normally.

NG -- REPLACE COMBINATION METER ASSEMBLY
OK -- Continue to next step.

2. READ VALUE USING TECHSTREAM (TACHOMETER)

(a) Check the Data List for proper functioning of the tachometer.

Combination meter





OK:

Engine speed on Techstream is almost equal to the actual engine speed.

NG -- GO TO SFI SYSTEM
OK -- Continue to next step.

3. CHECK ECM (TACH)





(a) Using an oscilloscope, check the signal waveform of the ECM.





OK:

Waveform is as shown in the illustration.

HINT
* As the engine speed increases, the wavelength shortens.
* Connect the oscilloscope's positive (+) lead to TACH terminal and negative (-) lead to E1 terminal.
NG -- REPLACE ECM
OK -- Continue to next step.

4. CHECK COMBINATION METER ASSEMBLY





(a) Using an oscilloscope, check the signal waveform of the meter.





OK:

Waveform is as shown in the illustration.

HINT
As the engine speed increases, the wavelength shortens.

NG -- REPAIR OR REPLACE HARNESS AND CONNECTOR

OK -- REPLACE COMBINATION METER ASSEMBLY