Twobeers
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| posted on 29/1/26 at 11:20 PM |
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ST170 cam sensor polarity
I'm changing from a zetec engine to a zetec/st170 engine and this has a different cam sensor plug to the blacktop. I've sourced another plug
to suit the sensor but not sure what the polarity should be for the plug wiring.
Currently as you look at the plug for the blacktop from the wiring side the earth is on the left and the signal is on the right. Is it the same on the
ST170 plug? Looked everywhere but can't find the answer.
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Theshed
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| posted on 31/1/26 at 11:27 AM |
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I assume it is a three wire hall sensor? If so this might help
https://support.haltech.com/portal/en/kb/articles/determining-hall-effect-sensor-pinouts
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obfripper
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| posted on 31/1/26 at 06:55 PM |
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Have a close look at the sensor, normally the polarity is embossed into the plastic near the plug, or marked inside the plug down by the pins.
If you can't see it, connect both wires to a multimeter set on dc low volts range, place a steel object next to the sensor tip and sharply pull
the object away, this should give a brief negative pulse. If the pulse is positive, then swap the polarity and recheck. The pins can then be assigned
to their correct polarity as per the meter leads.
It is a vr sensor, so the signal will be approx 3v ac while cranking, and rise to approx 30v at red line, the ecu conditions this signal in to a
digital input.
The ordinary zetec cam has one trigger tooth, the st170 has 5, with 4 at 90°, and one at 45° between 2 teeth, so give quite a different looking
signal from otherwise similar sensors.
Dave
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Twobeers
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| posted on 1/2/26 at 12:22 AM |
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Many thanks, I have some markings on the aftermarket plug which indicates pin 2 as GND. I've been advised that as it's a 2 pin plug no
damage will be done if it's the wrong way round, and certainly will have a go with the method you advise.
Whilst it's a st170 cam, it's an aftermarket re grind so will not be using VCT, I've ground off 4 of the teeth just leaving one to give
the ECU a reference in the same way the blacktop single signal does.
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