Hello all, I'm new to the forum and I have a Jeep that won't start.
It overheated in a parking lot, died, and hasn't started since. None of the gauges on the dash worked, aside from the battery voltage and oil pressure gauges, if I remember correctly... In the parking lot, I replaced the crankshaft and camshaft position sensors, and the PCM. After getting pissed off, I sent it to a mechanic so they could deal with it.
$1,000 later, they couldn't figure it out. They replaced some of the wiring harness, and dug around for a long, long, looong while, but had no luck. And so, I am reassured that the money spent on mechanics is rarely ever worth it.
Anyways, after getting it back to my place via a towstrap, a buddy with a pickup, and guts, I fiddled with it and got ALL the gauges working aside from the tach within 2 hours. Woohoo! Well, mostly...
The fuel gauge does/n't work. It will read 0% indefinitely, that is until I reset the codes. Then, it will jump up! And then a few seconds later, go back to 0%.
I am getting codes P0122, P0123, P0118, P0113, and P1492. The first two relate to the TPS, the last to IAT and coolant temperature sensor (which I know is fried, at room temp it reads 8 ohms), the last is a manufacturer control.
The TPS is where it gets interesting...
The TPS, which has been replaced, while backprobed, on all 3 wires, shows 5.19V, and when off, shows .29V on all three. Now what in tarnation...
At one point, I had wired the TPS, IAT, and CTS grounds all to the (-) terminal on the battery, and it ran like **** for about 2 minutes before dying again.
To me, it sounds like a wiring issue, or perhaps an issue with the PCM? I'm at a loss and want to dump it in a lake. If I hadn't bent the frame on my EF civic I would already have done that.
I've replaced the grounds on the block, checked continuity between the PCM and those grounds, and all checks out there.
If it is a wiring issue, is there anywhere in particular I should I look? I went one by one and started disconnecting the sensors connected to the circuit to see if anything changed. Disconnected IAT, CTS, battery temp sensor, and O2 sensors... No change.
Any advice is appreciated. Thanks in advance!

It sounds like a short, or leakage in the wiring or connectors to one of the sensors.

there is a very good Youtube somewhere on diagnosing this issue
most of the sensors share a common 5V supply

Do you have 5V and Earth on the other sensors ?

Yeah I agree with the above guy talking about the 5v lines. If one of those wires is shorted you will run into some crazy problems. From my memory (I may be forgetting a few but you can see them all in the factory service manual) the 5v runs through the follow sensors:

TPS
Crankshaft PS
Camshaft PS
Vehicle Speed Sensor
Oil Pressure Sensor
MAP sensor

check for 5v on those, like i said there might be some others im forgetting