What's inside a throttle position sensor?

Discuss, ask, or get help with engine and mechanical queries in here.

Moderator: Moderators

Post Reply
User avatar
rwb
3.0 24v
Posts: 2510
Joined: Thu Jun 17, 2010 7:53 pm
Location: Yorkshireman exiled in Salop
Contact:

What's inside a throttle position sensor?

Post by rwb » Wed Dec 26, 2012 4:51 pm

I have a duff one, and since apparently it's possible to take it apart I thought I'd have a go and see.

This is it.
Image

That cover comes off easily enough.
Image
Underneath is a slightly sticky transparent rubbery stuff that covers a metal plate behind which there appears to be a circuit board.

These blobs prise off easily (I think they're the same rubbery stuff)...
Image
...to reveal two torx head screws. I'm not sure what size they are: the bit says T20 and the socket says T15 but both are the same size and fit.
Image

Anyway, the two halves come apart like this:
Image
The big half (to which the cable attaches) has a flat headed spindle that fits into a slot on the electronic half. Both halves are sprung.

Three small torx gets you further into the electronic half.
Image
See there's a slot in the cover (at about 10 O'clock) that fits into the main part (at about 9 O'clock).
There are (at least) two different ways to put this back together, and in some of the ways the thing will not move at all.

Now this was a surprise. Taking out the spring, you find that the slot is on the back of a plastic thing that holds two semi-circular magnets.
Image
On the back of the plastic thing (this is the bit that gets turned by the other half) there is a lug at about 10 O'clock that fits into a channel that runs from about 7 O'clock round to about 1 O'clock. Thus the thing can only turn through one half turn.

That is as far as you can get into the electronic side without gouging out the rubbery stuff. So that's as far as I got with that.

Back over on the half to which the cable attaches, there's a circlip round the shaft. This comes off easily enough, although once off it will never hold as tightly as it did.
Image
As well as the ring for holding the circlip, the shaft has a slot into which a lug on the inside of the washer fits to prevent it from turning.

With the circlip off the thing springs apart quite readily to reveal nothing more exciting than two springs.
Image

By the way, a 'grainy' feel when you twist the TPS is muck in the springs and round the pastic parts that move against eachother.

For the record, this is what I measured across all combinations of the 4 terminals:
Image
(by '40+' I mean 'a bit more than 40 actually but I assume that it's supposed to be bang on 40')
Last edited by rwb on Wed Dec 26, 2012 5:07 pm, edited 2 times in total.

R-plate 406 1.9 TD LX (1 year) | 02 406 2.0 HDi (90, Siemens) GLX+nav (8 years) | 07 407 2.2 HDi GT (since 2013) | 307cc 2.0 180 | Map of PeugeotForums users offering PP2k

User avatar
rwb
3.0 24v
Posts: 2510
Joined: Thu Jun 17, 2010 7:53 pm
Location: Yorkshireman exiled in Salop
Contact:

Re: What's inside a throttle position sensor?

Post by rwb » Wed Dec 26, 2012 5:00 pm

So, questions:
* How does this magnet thing work?
* Are there any moving parts that I haven't seen?
* How do you get further into it? Gouge the rubbery stuff out?
* What can you actually do to fix a TPS reporting intermittently out of range values or open curcuit?

R-plate 406 1.9 TD LX (1 year) | 02 406 2.0 HDi (90, Siemens) GLX+nav (8 years) | 07 407 2.2 HDi GT (since 2013) | 307cc 2.0 180 | Map of PeugeotForums users offering PP2k

madmadmax
2.0 Turbo
Posts: 484
Joined: Sun Jan 01, 2012 6:49 pm
Location: sheffield, south yourkshire

Re: What's inside a throttle position sensor?

Post by madmadmax » Wed Dec 26, 2012 5:40 pm

ok to fix the tps fault it most of the time is the grease getting conductive metal partials in, over time it reaches critical mass and the grease becomes conductive thus giving faulty reading

the grease lubricated the two magnets so clean this out and re-grease the two magnets problem fixed

the sensor is an inductive one so to get a reading there must be a inducer and exducer(i don't know if this is the right terms) one to give and one to receive a reading the tps has two sensor in it an a and b circuit to be able to verify the reading

http://en.wikipedia.org/wiki/Inductive_sensor

Post Reply