Meter / Gauge System Malfunction In Tachometer

WIRING DIAGRAM

INSPECTION PROCEDURE

PERFORM ACTIVE TEST BY INTELLIGENT TESTER

READ VALUE OF INTELLIGENT TESTER (ENGINE SPEED SIGNAL)

READ VALUE OF INTELLIGENT TESTER (ENGINE SPEED SIGNAL)

INSPECT COMBINATION METER

CHECK HARNESS AND CONNECTOR (COMBINATION METER - ECM)

WIRING DIAGRAM

INSPECTION PROCEDURE

1. Operate the intelligent tester according to the display and select the "Active Test".
   
   

   Combination meter:

   
   

   Item	Test Details	Diagnostic Note
   TachoMeter Operation	0 rpm / 1,000 rpm / 2,000 rpm / 3,000 rpm / 4,000 rpm / 5,000 rpm / 6,000 rpm / 7,000 rpm	-

   OK:

   Needle indication is normal.
   

1. Operate the intelligent tester according to the display and select the "Data List".
   
   

   Combination meter:

   
   

   Item	Measurement Item/Range (Display)	Normal Condition	Diagnostic Note
   Engine Rpm	Engine speed/ Min.: 0 rpm, Max.: 12,750 rpm	Almost same as actual engine speed (when engine is running)	-

   OK:

   Engine speed displayed on the tester is almost the same as the actual engine speed.
   

1. Operate the intelligent tester according to the steps on the display and select the "Data List".
   
   

   ECM:

   
   

   Item	Measurement Item/Range (Display)	Normal Condition	Diagnostic Note
   Engine Speed	Engine speed/ Min.: 0 rpm, Max.: 16,383 rpm	Almost same as actual engine speed (When engine is running)	-

1. Check the input signal waveform.
   

   1. Remove the combination meter with the connector still connected.
      

   2. Connect the oscilloscope to terminal L31-27 and body ground.
      

   3. Start the engine.
      

   
   
   

   4. Check the signal waveform of the connector.
      

      Item	Condition
      Tool Setting	5 V/DIV., 10 msec./DIV.
      Vehicle Condition	Engine idle speed

      OK:

      As shown in the illustration
      

1. Disconnect the A7 ECM connector.
   

2. Disconnect the L31 meter connector.
   

3. Measure the resistance of the wire harness side connectors.
   

   Standard resistance:

   Tester Connection	Condition	Specified Condition
   L31-27 - A7-16	Always	Below 1 Ω
   L31-27 - Body ground	Always	10 kΩ or higher