crooster

I'm in the middle of a throttle body reseal using the Arnnworx kit as part of tracking down an idle issue. The car is running fine otherwise. I thought I would check the throttle position sensor while I had the throttle body off. Now I have a bit of a head scratcher. My readings are opposite to what Clark's Garage and the Arnnworx site say are normal readings. Here is what Clark's says:

For turbocharged cars:

Disconnect the electrical connector for the DME control unit.

Connect an ohmmeter between terminal 2 on the DME wiring harness plug and ground. This will check the idle contact.
With the throttle closed, the ohmmeter should read between 0 - 10 ohms. With the throttle open, the ohmmeter should read infinite (∞). The switch in resistance must occur as soon as the throttle starts to open (approximately 1°).
Disconnect the electrical connector for the KLR control unit.
Connect an ohmmeter between terminals 22 and 23 on the KLR wiring harness plug. With the throttle closed, the ohmmeter should read between 320 - 670 ohms.
Slowly open the throttle to the wide open throttle (WOT) position. As the throttle opens, the resistance should continuously increase to full open resistance without any breaks. Full open resistance is 2.7 - 4.7 Kohms.

So as the throttle is opened from idle the resistance should increase from 320-670 ohms to 2.7K - 4.7K ohms.

My TPS reads 3.76K ohms at idle and 470 ohms at full throttle so the resistance is decreasing rather than increasing as the throttle is opened. The resistance appears to change smoothly as the throttle is operated. I'm having trouble understanding how this could occur if it is indeed a failure.

For reference here is more info from Bruce Arnn's site:

http://arnnworx.com/tps-repair.htm

Note that I measured directly at the TPS switch, not the KLR, on pins 1 and 3.

Any ideas?

F18Rep

Any chance you are open between pins 1 & 2?...Bruce

crooster

No - it reads 4.2 Kohms between pins 1 & 2 (and this is constant thruout the throttle range). Puzzling...

crooster

Anyone got a spare 951 TPS they can try this test on? If mine really is "backwards" I can't imagine that the car would run properly since the signal to the KLR would be wrong.

BTW - the throttle shaft seals in my throttle body were in bad shape. I highly recommend the Arnnwork rebuild kit. Good instructions to work you thru the process.

crooster

Mystery solved. The test procedure says to measure resistance at the KLR pins 22 and 23. This corresponds to pins 2 & 3 on the TPS according to the schematics, not 1 & 3 as I was using. In hindsight this should have been obvious. I may have to return my EE degree!