Chrysler Repair: 98 dodge/ throwing codes for TPS but wont fix, throttle position sensor, tps code

Question
i have a 98 ram and it was throwing two codes, throttle position sensor voltage too high; the other, throttle positon sensor voltage too low. replaced the TPS, now its still throwing TPS full throttle-NOTE- it runs great, until i turn on the a/c, clear the code it runs great, turn on a/c throws it right away. when the code is thrown, when im driving(60-65mph), i can feel the transmission rnadomly downshifting then upshifting. any takers? cant figure this one out! any help greatly appreciated.  

Answer
Hi Joe,
I thought immediately of the AIS when you said that when you turn in the A/C the check engine light came on.  The AIS is supposed to raise the idle speed which it probably wasn't doing. Did you have the code # wrong? The mil for TPS is 23/24, while that for the AIS is 25. So I would have expected a 25 code or P0505 if the AIS was bad. But why the TPS code is beyond me. Thanks for the feedback and evaluation.
Roland



Hi Joe,
The TPS is a simple potentiometer with 5 volts at one end of a resistive element, ground at the other end, and a movable sweeper that skims over the surface. The three wires are similarly arranged at the plug with the sweeper in the middle. Because the sensor was changed out, the remaining code must mean there is an issue with the wiring harness from the there to the PCM. It may be that the wires got overheated and are shorted together.
I don't have a wiring manual for the trucks, but on the car lines those 3 wires go to pins 61, 43 and 35 respectively. But the color assignments are uncertain. By means of an ohmeter you should be able to check continuity of the wires to the pins. The wire on 43 should be a common ground for other sensors on the engine, the wire on 61 should have 5 volts when the ignition is on, and the wire on 35 should vary between about 0.3 and 4.3 as you move the throttle. So check those connections and voltages. If that checks out, then it may be the PCM but I would be reluctant to change that without further corroboration, because of cost.
I have the TPS "tree-type" troubleshoot for several of the car engines for '98 and can xerox the 8 pages and postal mail those to you. I can do that for the cost of 3 39-cent stamps that you can send back to me after you get them. Let me know by a "rate volunteer" comment if you want these and tell me a postal address.
Roland