Testing the Hall Sensor

[JKlaveness]

Hi,

Is there anything special I need to be aware of, when I check the signal from the Hall Sensor on a 16V n/a 2 litre engine?

Last week, my daughter's c900 "died" while it was idling in a parking-space. I ran a few tests on it, as recommended by the Bentley Bible, and found no signal from the Hall Sensor.

I changed the Hall Sensor, but the engine was just as dead as before, and there was still no signal on the relevant pin at the EZK connector.

I did the measurement exactly as recommended: Lifted a front whell, engaged fifth gear, turned the ignition on, connected my voltmeter to the relevant pins on the EZK connector, and turned the front wheel round, verifying that this caused the engine to rotate. I checked several times that I was doing the measurement at the right points, and that the probes had a good electrical connection with the metal.

At this point, I checked the rotor in the distributor, and found that there was no connection through it. A new rotor and distributor cap solved the problem: The car started immediately.

Last time I checked a Hall Sensor, I got normal readings. However, that was on an Automatic, and I used the starter motor to turn the engine over. Could this have made a difference?

Does anybody have an explanation?

[Jim Mesthene]

There are no conclusive tests for the Hall Effect Transmitter (despite what your Manual says).
In diagnosis, the only way to rule it out is to "test by substitution".