Picked up a 1998 XJ a couple weeks ago. It's a 4.0/ auto with 191k miles.

When I bought it, guy said it needed a new computer because the computer is always showing throttle is 100% open.

Anyway, when it's started the idle is erratic and if left alone it will eventually die. When I hit the gas it seems to idle around 1200-1500 rpm.

The check engine light, airbag light, and check gauges lights are lit up. It's showing codes P0122 (throttle/pedal position sensor low) and P0123 (throttle/ pedal position sensor high).

I read about the clock spring possibly causing the issue. I removed the horn relay as one thread mentioned that would eliminate that. No change. I removed TB and cleaned, but it wasn't very bad. Took out the IAC, and there seemed to be a lot of carbon build up on it.

What would be the recommended/ most likely route to go as far as things to check/replace?

Thanks in advance

I would test the throttle position sensor first. Backprobe the flat 3-pin connector on the TPS while connected with the key-on. You should see 5-volts on one wire, ground on the other, and the voltage on the signal wire should change smoothly from around a half voltish to 4.5 volts (ballpark). The ground wire should only have under a few ohms of resistance to the battery ground.

Is it shifting okay? A bad throttle position sensor will throw off the shift points as well.

Seems silly, but it has good gas?
In the tank?
if you just picked it up, what have you done to it?
How long has it been sitting?






Good Luck, and God Bless!

A few obvious possibilities, a faulty TPS, or a bad wire/or connection back to the PCM.

I would verify a low resistance connection by backprobing the relevant terminals, then consider testing/replacing the TPS (but dont throw away the old one)

I had this once and the female pin on the connector had been pushed back, so no contact was made, similar codes

Anybody have the MOPAR part number for TPS? I’m having a hard time locating one.

Also, any recommendations on PCM in case I need it? I’ve seen online from $250-400.

From the parts catalog => 4874371AC