The tach has stopped working on both my autometer gauge and when I connect the computer up to the ATS tranny controller.

I traced down one of the wires and AutoWorld installed a sensor on the crank. I assume this is item is not stock. Anybody have any experience with these? How do you tell if one has failed?

Also, isn't there a pin on the PCM connector that you can use as 'tach out'?

Peter

 

No pin on the ECM connector for a "tach out" signal. That would be too easy.

Do you have one sensor or two mounted to look at the tone wheel on the crank? From the factory there is one. I thought that Autoworld installed their own sensor and bracket to get a signal though...

I would check the simple things first, no loose connectors or bad connections. When does the signal input wire to the tach go to? Straight to the sensor on the crank? I would have thought they needed to use a interface box like those at dakota digital.

 

You can see my factory mounted crank sensor in this pic...

 

There's a separate sensor for the tach. Either the gauge is dead or the tach has died - I checked the wiring and it look OK, I have to pull apart the harness up at the front of the engine to really check. How do you test the sensor for operation?

Peter

 

The best would be a scope , they check faster than anything els , so if there is a glitch they catch it where a multi meter will not , with a glitch , it may still get eng running , but maybe not smooth .
Then is the sensor a 2 wire or 3 wire ?
Connecting a multi meter to the right 2 wires should give varying voltage of around 3-5 volts .

 

Two wire.

I have no scope and no access to a scope - it may be handy to have in the future wtih two computer controlled engines to fix.

I was wondering if I pulled the sensor and waved a magnet next to it if I could watch the pulses.

But probably first I should check the tach itself - I have a hard time imagining a simple inductive sensor failing - but then why would the tach die all of the sudden. Can I just ground the sensor wire rapdily by tapping on it and hope to see a response from the tach?

Peter

 

The sensor has a magnet in it now. Anytime a notch in the tone ring passes in front of it, the magnetic field collapses, and induces a current in the sensor. I believe it has a built in resistance such that you would see a voltage spike (differential) between the two wires.

So, if you hold it against something metal with the two wires connected to a voltmeter, and you quickly pull it away from the metal, you could theoritically see a voltage spike. However, it is very small and short in duration. I am going to guess that you won't see it (but I have been wrong before).

Now you could hook up your multimeter to the two wires (and leave the sensor mounted on the engine), start it up so that it is creating 60 pulses per revolution and you may see a steady voltage on your meter.

Something I just thought of to check, did the sensor just get bent out away from the tone ring? I was thinking that it had to be within 0.020" or so to work?

 

The sensor is mounted on a very, very beefy bracket. I can't have moved. I need a scope, but I'll try the multimeter and see if there's nothing - that might be a clue.

Peter

 

Finally got the sensor off and the lower half is totally gone. A rock or piece of gravel must have gotten up in the belt and broken it off. Next thing is to figure out what what the hell sensor I have. This sensor is looking at dedicated ring with 4 metal tangs or bosses mounted on it for the senor to read. The only writing I can find on the sensor is 6M06 but googling that produces nothing.

Unlike all the sensors on Summit, this one has a black plastic house and 90's immediatly into a connector, so it is very low profile.

Peter

 

I'd call autoworld and see what they used...

 

I've got a call into them, but it could be days before I hear back.

Peter