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Proximity switch/sensor testing?

New to the group, so apologies if this question has been asked before.

My car is fitted with a sensor that tells the ECU that manages the auto gearbox what RPM's the engine is running at. The error code on the car points to the sensor not sending the RPM's to the ECU Before I fork out £60 for another sensor is there a way of using digital multimeter to test it? The unit is a plastic moulding with two wires, and has quite a strong magnetic field.

My level of expertise?....Novice!

All help appreciated.......ttfn........Alistair

Reply to
Alistair Ross
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Sounds like a generic Hall Effect Vehicle Speed Sensor/Switch. I've never found away to test them, but the failure mode is no signal to the vehicle's computer, so the error code gets set. Depending on if it is the input (engine to trans shaft speed) or output (trans output to vehicle wheels) that failed some other nasty things can happen as well since these speed sensors are used to determine the automatic transmission's shift points and also sends the vehicle's speed to the speedometer.

I have found that these fail fairly often. I have replaced 4 of them in several different makes and models of vehicle over the last 15 years. The last one was last year on a minivan that had about 40K miles. They are usually pretty cheap ($30) and easy to locate and replace. My only advice would be to make sure you have the correct one since in most vehicles there are two (input and output).

Good luck.

Bob

the

Reply to
Bob Shuman

These sensors, are not able to be verified with an ohm meter. They are usually a Hall effect device. These also have different specs, depending on their designed application. The testing of one of these is fairly complex.

You could run the motor, and see on a scope the output of it, but you would have to know the exact characterises in the waveform that you are supposed to have. This would be the amplitude, timebase, and its form. The dealers and service centres would have dedicated test facilities to test these devices, and to be able to test the computer unit as well.

It is possible that the sensor, or the computer that is reading it may be defective, or it may be a simple wire or connector problem. The best test is to substitute the parts. This is why it may be cheaper to go to a service centre to have them check it for you. You will have to buy the parts to try them, and I don't think they are returnable.

--

Jerry G.
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"Alistair Ross"  wrote in message 
news:d192fb$f2n$1@gemini.csx.cam.ac.uk...
New to the group, so apologies if this question has been asked before.

My car is fitted with a sensor that tells the ECU that manages the auto
gearbox what RPM's the engine is running at.
The error code on the car points to the sensor not sending the RPM's to the
ECU
Before I fork out £60 for another sensor is there a way of using digital
multimeter to test it?
The unit is a plastic moulding with two wires, and has quite a strong
magnetic field.

My level of expertise?....Novice!

All help appreciated.......ttfn........Alistair
Reply to
Jerry G.

Thanks....ttfn........Alistair

Reply to
Alistair Ross

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