A Look Inside A Throttle Position Sensor

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May 6, 2006 | 10:04 PM

aerocolorado

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A Look Inside A Throttle Position Sensor

I replaced my TPS recently to fix a locking/unlocking problem with the overdrive solenoid. I took the old one apart just to see what makes it tick. This is the original Ford TPS with 251,000 miles accumulated.
The first picture is a look at the various components: spring, orange cam with two small multiprong wipers, TPS body and the circuit board.

The next picture is a close up of the cam and circuit board. If you look closely at the circuit board, you can see a shiny area where the wipers wore down through the coating on the circuit strip. This was causing an erratic signal to the PCM. Also note on the first picture the circuit board has a lot of black grime. I wiped this away for the second picture. I was surprised how much was inside the TPS even though it is a sealed unit. There is a rubber seal on the orange cam but it looked like it had seen better days.

Last edited by aerocolorado; May 6, 2006 at 10:08 PM.

May 6, 2006 | 10:54 PM

96_4wdr

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From: Washington state

thanks AeroC,

great photos......250k miles- a trip to the moon
original engine?

May 6, 2006 | 11:09 PM

lv2race

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From: The OC

I like to do the same thing when I replace components. I take them apart and see what makes them tick!

Thanks Aero!

May 7, 2006 | 12:14 AM

aerocolorado

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Quote:

Originally Posted by 96_4wdr

original engine?

Yes, its the original as is the transmission. Neither one has ever had any major problems. I've really been impressed with this 4.0L engine. The old gal faithfully hauls me 50 miles round trip daily. Last week was the first time being stranded when the belt tensioner pulley inexplicably fell off.

May 7, 2006 | 12:28 AM

Piffery1

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From: Niceville, FL.

The black "grime" is actually the carbon particles worn away from the restistive area that is now shiny, so it came from the inside and not through the seals. There are variable resistors (potentiometers) internal to many cruise control servos that fail in the same manner and can cause "failure to lock" or "hunting".

May 7, 2006 | 01:40 AM

krankshaft

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From: North Jersey, New Jersey

Yep thats one of the major design flaws of pots since the wiper is in constant contact with the carbon on the wafer (PCB) its only a matter of time before it gets eaten up. But at 251K it had a good long life.