Gremlins in my 1998 1500

[Raceace26]

For several months now I've been fighting a high idle issue and by applying throttle the engine speed will remain even higher upon letting off the gas. I changed the TPS with no difference made and cleaned the IAC with no effect. I would think a vacuum leak but if I unplug the TPS the engine sputters then idle drops to normal level. Plug TPS back in and high idling again.

Next, I had to change my fuel pump this past Saturday and removed the bed to do it. All went well and in two hours job was done and truck running normal excluding the idling issues. Sunday drive three hours into Alabama to tow a jet ski for friend on the way pulling a slight hill with cc on set at 80mph the truck just slowed to near 65 turned cc off etc, got back up to 80 reset cc and continued without a problem again. Monday my friend drove the truck 50 miles to work and as he got there said the check gauges and battery light came on. I went and put volt meter on battery with truck off and got 12 volts, started truck and tested again at battery and got 11 volts... alternator is bad. I take it off and go to O'riellys auto parts have them test and it failed 3 times. Put new alternator on it and think it's all good. He messages me 10 miles from home, on interstate all of a sudden Rpm's go through the roof and the cel is on. He stops and checks the cel's and gets these...P1682, P0748, P1765 (I have two scanners so I know what the codes mean/say) he limps home and shuts it down. I look yesterday checked battery connection, 3 grounds in engine bay I can find and one on the bed of truck I know of, all solid, tight, no corrosion. Wiggle wires on tranny and all seem normal. Check fuse and swapped relay (did not test relay socket though) for transmission, made a jumper wire from pink wire on middle cluster of PCM. to the negative battery and after all that I get codes P0743, P1765.

I changed the alternator once before and had no issues like this so I'm very confused about where to go/look. I thought perhaps the solenoids in the tranny, or a new PCM but I don't want to just throw parts at it blindly... ANY ideas? Battery is about 1 year old +/- but seems strong.

Truck has about 50,000 on the tranny with never an issue. Shifts solid and good prior to this, there's about 10,000 miles on the tranny fluid in it as I did a motor job and changed tranny fluid then, and it's still clean and red.

1998 1500 sport club cab 5.9l 360 4x4 auto
Super chips programmer (although it's currently back to factory settings)

 

[dudeman2009]

Well, for the Idle, did you do the APPS reset procedure after replacing the TPS?

1. Set parking brake
2. Disconnect negative battery cables on both batteries
3. Turn ignition key to run(to drain any remaining capacitors)
4. Let truck sit for 30 minutes( this is the recommended minimum)
5. Return ignition to OFF position
6. Reconnect both batteries and secure, not a timed event
7. Turn key to run position(not start) and depress accelerator pedal slowly all the way to the floor
8. Allow pedal to return to top position slowly
9. Repeat twice more
10. Turn ignition switch OFF
11.Release parking brake
12.Start the truck and let it idle for 3-5 minutes without touching the throttle.

That should reset it. If it doesn't you can try it again, sometimes it takes a few tries.

As for the codes. You'll have to fix P1765 first. An open or shorted condition is detected in the Transmission Relay control circuit.

I looked it up in the wiring diagrams, its seems the reference circuit is tied into the alternator control circuit. Why, I have no clue. What that means, the two pin connector on the alternator, check to make sure it's securely plugged in and the wires are free from damage.