Tachometer Malfunction: Procedure

1. Connect the Techstream to the DLC3.
2. Turn the engine switch on (IG).
3. Turn the Techstream on.
4. Enter the following menus: Body Electrical / Combination Meter / Active Test.
5. Check the operation by referring to the values in the table below.
   COMBINATION METER
   
   

   Tester Display	Test Part	Control Range	Diagnostic Note
   Tacho Meter Operation	Tachometer	0, 1000, 2000, 3000, 4000, 5000, 6000, 7000 (rpm)	Confirm that the vehicle is stopped, engine idling

   OK

   Tachometer indication is normal.

NG → See step   6 

OK: Go to next step 

1. Connect the Techstream to the DLC3.
2. Engine start.
3. Turn the Techstream on.
4. Enter the following menus: Body Electrical / Combination Meter / Data List.
5. Check the values by referring to the values in the table below.
   COMBINATION METER
   
   

   Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
   Engine Rpm	Engine speed/Min.: 0 rpm, Max.: 12750 rpm	Almost same as actual engine speed (tachometer indication)	If data received from the ECM exceeds the range that can be displayed on the meter, the meter continues to display the maximum value of the range.

   Result

   Result	Proceed to
   The tachometer indication differs from the engine speed displayed on the Techstream.	A
   Engine speed displayed on the Techstream is almost the same as the tachometer indication.	B
   Both the tachometer indication and the engine speed displayed on the Techstream are 0.	C

C → See step   4 

B → See step   3 

A → See step   6 

1. Connect the Techstream to the DLC3.
2. Engine start.
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine and ECT / Data List.
5. Check the values by referring to the table below.
   ENGINE AND ECT
   
   

   Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
   Engine Speed	Engine speed/Min.: 0 rpm, Max.: 16383.75 rpm	Almost same as actual engine speed (tachometer indication)	-

   OK

   Engine speed displayed on the Techstream is almost the same as the tachometer indication.

NG → See step   7 

OK: Go to next step 

1. Disconnect the A5 and J34 connectors.
   Fig 1: Checking Harness And Connector Between Combination Meter And ECM

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A5-15 (TACH) - J34-16 (S)	Always	Below 1 Ω
   A5-15 (TACH) - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Check the input signal waveform.
   Fig 2: Inspecting ECM (Input Waveform)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   1. Reconnect the A5 ECM connector.
   2. Connect the oscilloscope to the terminal J34-16 (S) and body ground.
   3. Start the engine.
   4. Check the signal waveform according to the condition(s) in the table below.

      Item	Condition
      Tool setting	5 V/DIV., 10 ms./DIV.
      Vehicle condition	Engine idling

      OK

      The waveform is displayed as shown in the illustration.

      HINT: 

      When the system is functioning normally, one engine revolution generates 4 pulses. As the engine speed increases, the width indicated by (A) in the illustration narrows.

NG → See step   8 

OK → See step   6