boston944turbo

I ran the blink code test on my 86 951 as it has not been boosting correctly. Codes 3-3 and 4-1 came back which should point to the TPS.

I then checked resistance at the DME plug 2 at closed and open throttle and that looks fine.

However when I checked the KLR plugs it looks like there is a problem. If I read voltage at pin 22 it comes back very low and does not increase as the throttle is opened. Also, resistance between pins 22 and 23 looks to be infinite no matter what the position of the throttle is.

Any ideas how to check the TPS itself? Is it possible to have a TPS that sends the correct signal to the DME but not the KLR? As the TPS has four leads I am hoping that is the case as the other possibility is the wiring or connnector itself. Any info would be appreciated.

Mike

Waterguy

Your throttle position switch actually consists of a switch and a potentiometer. Your first test shows that the idle switch is working properly. Your second test shows the potentiometer (that tells the KLR the actual throttle position) is not working at all. Yes, your TPS can work for the DME but not the KLR; the most common failure mode is the opposite of what you have, but yours can also happen.

To find out if it is the TPS and not the wiring, unplug the TPS and measure the resistance between terminals 2 and 3 on the TPS. Specs are the same as between terminals 22 and 23 on the KLR: idle position 320-670 ohms, varying smoothly as the throttle is opened to 2700 to 4700 ohms at WOT. If the TPS works but you don't get the readings between terminals 22 and 23 on the KLR (key off), the problem is the wiring/connections.

I haven't heard of anyone fixing the TPS; they seem to last about 100k miles, more or less, and cost about $50 to replace. Just replace it.

Good luck with it, and post your results! <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />

boston944turbo

Waterguy,

Thanks for the help. I checked the resistance between terminals 2 and 3 on the TPS and it is infinite. Looks like the wiper inside the TPS is broken. I then jumpered the leads on the connector under the hood and did a conitnuity check inside on the KLR box which worked fine. It looks like the wiring is fine and the culprit is a 50.00 TPS. Good news!

Mike

Waterguy

Glad you got it sorted out. Don't know where I got the idea that you wanted to fix the TPS; too many people retracking their AFMs, I guess.

That price was from an after-market source; you may pay more through your local dealer.