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Discussion Starter #1
Hi
Does anyone have the correct resistance readings for the above sensor?

The circuit suggests there are 2 potentiometers, however what I am reading doesn't reflect what I expect a potentiometer to do.

The car had had a "new" sensor fitted but if its new new or new secondhand.

Across the two pots I see 1.61K (1-5) and 890 ohms (2-4)
Pin 1-6 gives me 2.4K pedal up and 1.99K pedal down. Not what I expect to see from end to wiper.
Pin 2-3 gives me 1.69K pedal up and 1.17K pedal down. Again not normal potentiometer response.

If I remove the screws and lift the cover is this thing going to explode with a flurry of springs like an old clock?

Thanks
John
 

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I guess the components are variable resistors, ie. variable between a max and min value, no end stop like a pot.
You got a cct diagram?
 

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Discussion Starter #3
Pin 1 is on the right in this image.
IMG_0006.JPG


IMG_0011.JPG
I guess the components are variable resistors, ie. variable between a max and min value, no end stop like a pot.
You got a cct diagram?
I ended up pulling it apart. Its a few carbon tracks joined by dual wipers. I can see wear marks on the end of a couple of the tracks .

Yes, I have a circuit diagram.
 

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What's the issue your having. From experience the pedal sensors dont tend to go wrong. Every car I've ever seen with the pedal or throttle codes have been ecu failure.
 

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I'd say if 1-6, and 2-3 are the two circuits then the resistance range readings for both from closed to open throttle are about the same (400k). I'd clean the tracks and wipers with some alcohol, reassemble, refit it it and go follow the output voltages towards the ECU. If you find a volts drop check the wires' resistance and repair if necessary. (Sorry, I don't mean to sound patronising).
What was the original issue that made you go looking, Riblit? Throttle response poor / none?
 

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Discussion Starter #6
@marks152 it would sometimes refuse to accept that the accelerator pedal was being depressed. I'm still waiting for my opcom purchase to arrive so have been looking around and thought I would check the pedal sensor resistance as it is a second hand one someone else put in the car. One of the two 5V inputs would drop to 3V.
From what I have read, most ECUs have a single 5V regulator that supplies all the sensors so having one line drop to 3V suggests an intermittent high resistance. I've cleaned all the interconnecting plug/sockets with servisol - a contact cleaner I use on electronic equipment.

@SickStings, intermittent refusal to accept that the accelerator is being depressed.

The car belongs to my Granddaughter's partner. I don't know much about its history except that the throttle body looks like it has been replaced, likely with a second hand one. Its rego is almost up and he has another vehicle now so it's not really important. I thought it would be an interesting problem to solve.

John
 

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That's gotta be a nightmare when you pull out and have no motion, John; scary.
Your issue now is you'll have to catch this bugger in mid-fault or you'll be chasing your tail. If you know where the pedal wiring goes next / or ends up then measure resistance mid point (or wherever is possible) and that should lead you one way or the other. I'm guessing a bad connection at the ECU (but I'm not Corsa familiar), but good luck with it, John.
 

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Discussion Starter #8
Its scarier when it happens at traffic lights and the car behind almost climbs into your boot.
I may have fixed it by cleaning all the connections between the pedal and the ECU. Either that or it's hiding.
Either way, the car owner isn't interested in re registering it so its destined to become a paddock basher.
If the opcom doover I ordered arrives by Tuesday I'll see what it tells me about real time voltages at the ECU, otherwise I'll find something else to keep my brain active.

John
 

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Think there are two variable resistors in there, one will read about 5v and the other about 0, with pedal on floor it will be round the other way,...from Fred in Essex.
 

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Discussion Starter #10
Think there are two variable resistors in there, one will read about 5v and the other about 0, with pedal on floor it will be round the other way,...from Fred in Essex.
That's not strictly correct. The only way you will see 5V on the wiper pin is if there is 0 ohms between the wiper and the end connection - achievable in a conventional potentiometer but not in the arrangement used in this sensor. If you scroll back to the photos I posted about 8 back in this thread you will see the wiper travel is less than the total length of the carbon tracks, also the two 5V inputs have an extra bit of resistance material between the socket and where that connect to the wiper tracks.

Also, both "wipers" are at the 5V end of their potentiometers at the same time. Both outputs travel in the same direction.

John
 

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It's rare to see much over 4.25v on sensor 1 and 2.1v on sensor 2,
sensor 2 should mirror sensor 1 @ 50%
There will be more than one 5v feed from the ecm though,it's fairly common to bridge from a single good feed when the other goes down
 

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Discussion Starter #12
It's rare to see much over 4.25v on sensor 1 and 2.1v on sensor 2,
sensor 2 should mirror sensor 1 @ 50%
That's good information! Sensor 2 at 50% of sensor 1. That is something that should be in the manual.

I've seen references to bridging the supply rails. That's feasible as all the 5V feeds usually come from a single 5V regulator in the ECU.
 
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