Tachometer Malfunction

METER: METER / GAUGE SYSTEM: Tachometer Malfunction

Tachometer Malfunction

WIRING DIAGRAM





INSPECTION 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