Hello All,

I'm hoping people here can help shed some light on the issues I'm having on my new project.
I have a '98 TJ, with a 5.9L and a 46RE from a 2003 Durango. I have a harness and a computer from a 1998 Ram. I merged the Jeep harness in to the Ram harness and have it running.
At first I had several codes, some related to the the wiring for the torque converter solenoid which I cleared out by fixing my mistake on the relay wiring.
Currently I still have two more trany codes, both related to the governor pressure sensor. I expect to clear these by swapping in a sensor from a '98 RE for the 2003 RE sensor I currently have. Apparently the newer sensor doesn't play well with the older computer.

My question is regarding the almost 2000 RPM I have at idle. I can bring the idle down to normal by unplugging the TPS harness.
Here is the test I've done to check voltage and function of the TPS:
https://troubleshootmyvehicle.com/ch...e-tps-sensor-1

Here are my results: (Wire numbers 1,2 and 3 are from left to right as looking at the TPS from the driver side of vehicle.)

Test 1: KOEO voltage to #2 wire is 4.6V and drops to 1.5V at WOT.
According to the test, it should be 0.5 to 0.9 and increase to 3.5 to 4.9 at WOT

Test 2: I have no KOEO voltage to wire # 3, but I do have 5V to wire # 1
I should have 4.5 to 5 VDC. Don't think I should have 5V to #1

Test 3 : And I'm getting only 7V to # 1 wire.
Should have 12V.

Also, I have 2 computers, both from Ram truck 1500 a '99 and a '98, 5.9L and 46RE, and two TPS sensors.. All combos give the same results. All sensors and computers are used.
So I'm thinking I screwed up on my wiring somewhere.
I connected it to the best of my knowledge and cannot tell where I went wrong. Here's what I have for the TPS wiring:

Wire # 1: Ground to computer pin # 4
Wire # 2: Signal to computer pin # 23
Wire # 3: 5V supply to computer pin # 17

Thanks for any help.

 

You already did all the troubleshooting. The TPS sends wrong information to the PCM which is what keeps the idle high. When the TPS is unplugged the PCM sees 0V which it interprets as throttle closed. From the description I'd guess 5V sensor power and ground are switched. Disconnect the connector, and with ignition on measure between #1 and #3. Pay attention to the polarity indicator on the multi meter.

 

It is the interpretation of the test results that I'm hung up on. I'm also thinking that maybe I crossed these wires somewhere along the way, or I have some other sensor hooked the wrong way along the path of the 5V supply and, or ground wire.

I tested wires 1 and 3 with the pos and neg leads of my cheap HF multimeter with the other lead connected to the appropriate terminal on the battery, here's what I got.

Pin 1 pos is 5.3 V
Pin 1 neg is 7.1 V
Pin 3 pos is .02 V
Pin 3 neg is 12.4 V

Did I do this correctly?

Thanks.

 

You could also just have measured between pin 1 and pin 3 directly, not between battery and the pins. In any case it confirms that the wires are crossed. You have 5V to ground at pin 1 which is the sensor supply voltage that should be on 3. (The reason you see 7V from battery + to pin 1 is that the voltmeter measures the differential between 12V and 5V which is 7V). Pin 3 is connected to ground as there is full 12V between battery + and pin 3.

 

I'll begin by apologizing to you. I screwed up on my # 1 and 3 wire to the TPS. I got them backwards. I was calling the 3 wire as 1 and vice versa.

I checked the voltage between and 1 and 3 and I do have 5V. I do not know what I may have screwed up on the last test to get possible different results.

I also physically followed all 3 wires from the TPS to the computer and all seem to be where they belong at the plug on the computer. The 5v supply and ground are providing power and ground to several other sensors, so now I'm fairly certain they are correct, since the vehicle seems to run ok. It's not been driven yet.

The TPS signal wire (#2) is going to pin 23 on the C1 computer pin and I'm fairly certain this is also correct.
I can follow these wires around because I just have the harness loosely taped together and mocked in place, there is no loom.

Is there something else I need to look at.I'm also wondering why there is no code for the idle issue.

Thanks again.

 

That throws me for a loop... The TPS on these is very simple, just a potentiometer that acts as a voltage divider. The observation "KOEO voltage to #2 wire is 4.6V and drops to 1.5V at WOT" would make total sense if the wiring is backwards. It should behave the other way around increasing the voltage towards WOT. To avoid confusion about the numbering let's go by wire identification colors.
- violet/white is 5V supply and connects to pin 17/connector 1 at the PCM
- orange/dark blue is the output to PCM to pin 23/connector 1
- black/light blue is sensor return a.k.a. ground to pin 4/connector 1
There should be +5V between the violet/white and black/light blue wires.

 

I'm not at home right now so I cant retest the voltage, but I did bring the ram and jeep computer pinout diagrams with me.

In looking those over, along with the TPS pinout from the two vehicles, I'm starting to realize I may have the 5v supply and the grounds reversed.

But if this is the case then all engine sensors are reversed, since all share the same 5v supply and ground.

Can the engine even run like that? It would be amazing if it can.

I'm thinking to reverse the wires on computer pin 17 and 4, this will switch 5v supply and ground to all the sensors. If that works, it should run like its supposed to. But if I'm wrong then am I risking damage to the computer by doing this?

What test can I use to see if wires are reversed. Right now I have a spaghetti mess of wires, colors, connectors and trying to sort through 2 different service manuals. This gets confusing real quick.

Another thought I have is that I may have crossed the wires on just he crank position sensor.
I'll double check that also.


Thanks again.

 

Pick a sensor connector, see which pins are supposed to do what, and see if they actually do.

 

I found some references to the TPS from a ram and a wrangler. Apperars the wiring is switched between the two. Dodge has the 5v on the right and ground on the left with the center wire for the sensor signal.
Jeep has that reversed, but keeps the center wire same. This is referenced from looking at the plug from the back as it is connected to the sensor.
Looks like I followed the jeep routing when I put it together.
I'll be home in an hour and my plan is to switch wires near the computer. I won't make a permanent connection at first. Just twist them together and see what happens.

 

I switched the wires and now have 5v to TPS on pin 3.
But I lost spark.
So to chase this, what would kill spark.
I checked distributer 5v signal and ground and that is good.
Ofcourse all that is now switched from before. I could not find a pinout for the distributor in the FSM. its probably called something else, like the alternator is referred to as generator

Unless anyone has any thoughts, I'm gonna pull the harness and go through it again.
At least now with a little better understanding.
Thanks again.