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Testing Tach wire at instrument cluster


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prince504 
Copper - Posts: 108
Copper spacespace
Joined: December 25, 2015
Location: United States
Posted: June 23, 2016 at 1:43 PM / IP Logged Link to Post Post Reply Quote prince504
I was testing the Tachometer wire at the instrument cluster on a 2009 Toyota Sienna and according to ReadyRemote --> white 40 pin plug, pin 37
Well I did find the exact wire & color at the pin but when I set my multimeter to AC and rev the engine, I got a reading btw 6-7V with engine at IDLE consistently. Reving the engine really didn't change it.
So I tested the wires at the fuel injector coil (non-common color) and the reading was going from 0.1 to 0.9V and revving the engine made it jump up.
Any ideas?
I ended up just going Tachless and adjusted crank time. Didn't want to run a wire to the engine bay. Yes am lazy.
i am an idiot 
Platinum - Posts: 13,693
Platinum spaceThis member consistently provides reliable informationspace
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Posted: June 23, 2016 at 4:49 PM / IP Logged Link to Post Post Reply Quote i am an idiot
Try putting the meter to DC volts. The voltage is actually a pulsating DC signal. Some meters will fluctuate with engine speed when on AC volts. Some meters need to be on DC volts.
sparkie 
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Posted: June 23, 2016 at 6:02 PM / IP Logged Link to Post Post Reply Quote sparkie
I have the tach wire listed as a BLACK/ Orange wire in pin 37 of 40 pin plug at cluster. Make sure that your meter has a good ground and you are getting a good contact to pin. Set meter to AC voltage.
sparky
geepherder 
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Posted: June 23, 2016 at 9:11 PM / IP Logged Link to Post Post Reply Quote geepherder
Bulldog lists BLACK/ orange pin 1 of the 35 pin ECM connector- behind the glove box.
My ex once told me I have a perfect face for radio.
prince504 
Copper - Posts: 108
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Posted: June 24, 2016 at 12:33 PM / IP Logged Link to Post Post Reply Quote prince504
i am an idiot wrote:
Try putting the meter to DC volts. The voltage is actually a pulsating DC signal. Some meters will fluctuate with engine speed when on AC volts. Some meters need to be on DC volts.
When I set my meter to DC volts, what reading should I be getting to look for? Thnx
prince504 
Copper - Posts: 108
Copper spacespace
Joined: December 25, 2015
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Posted: June 24, 2016 at 12:42 PM / IP Logged Link to Post Post Reply Quote prince504
sparkie wrote:
I have the tach wire listed as a BLACK/ Orange wire in pin 37 of 40 pin plug at cluster. Make sure that your meter has a good ground and you are getting a good contact to pin. Set meter to AC voltage.
Yea I found that exact wire. Since ReadyRemote had a picture of it, is was hard to miss. My ground and other connections were fine -- I used the same ground to test the wires at the ignition harness as well as Arm/Disarm wires...
prince504 
Copper - Posts: 108
Copper spacespace
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Posted: June 24, 2016 at 12:44 PM / IP Logged Link to Post Post Reply Quote prince504
geepherder wrote:
Bulldog lists BLACK/ orange pin 1 of the 35 pin ECM connector- behind the glove box.
I also went behind the glovebox to test that wire too using @kreg357 pictorial guide and got the same reading I got at the instrument cluster. I use the INNOVA 3320 for my testing
i am an idiot 
Platinum - Posts: 13,693
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Posted: June 24, 2016 at 2:45 PM / IP Logged Link to Post Post Reply Quote i am an idiot
Rev the motor and the voltage should increase.
kreg357 
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Platinum spaceThis member has made a donation to the12volt.com. Click here for more info.spaceThis member has been recognized as an authority in Electrical Theory. Click here for more info.spaceThis member has been recognized as an authority in Mobile Security and Convenience. Click here for more info.spacespace
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Posted: June 25, 2016 at 5:16 AM / IP Logged Link to Post Post Reply Quote kreg357
When it comes to the Tach wire, I have found that you can attach the R/S Tach Input wire and try a Tach Learn safely
without causing any harm to the vehicle. With the R/S units I use, the Tach Input wire has a very high impedance
and places virtually no load or interference on the vehicles Tach wire. While it is best to use all available wire
guides and other info sources to locate the wire and run the DMM test on it first, sometimes the real test is the actual
Tach Learn. If you have a high-end R/S system, you can always go to a F.I. or Spark Plug Coil, plus on many Toyota's,
Pin 9 of the OBD2 plug has a Tach signal.
Soldering is fun!
prince504 
Copper - Posts: 108
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Posted: June 25, 2016 at 7:37 AM / IP Logged Link to Post Post Reply Quote prince504
i am an idiot wrote:
Rev the motor and the voltage should increase.
Ok so next time I will try it in AC & DC mode...
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