AKXJJake

If my throttle position sensor is bad, would that prevent my tranny from shifting? on the way home from a local mud hole, i hopped on the highway, hit the cruise control on my 1998 4.0 automatic and all of the sudden, ECL comes on. I pull over, notice that its idling a lot higher than normal, and when i clear the code, it comes back, followed by trying to get back up to speed only to realize that I rev to 4k, finally shifts, then doesn't go into third. then, after i pull off again, it won't get out of second. along the way creeping home, i lose second, and it refuses to kick out of first. is the throttle position sensor really causing all this or did i get a sensor wet on the bottom of the 'ol XJ that i can clean out? i'm at a loss.

Radi

Absolutely. What code was tripping the CEL?

greenxj21

Could it also be tcu?

Radi

Possible but somewhat unlikely. The TCU decides when to shift based on the TPS input and several other things. It then operates solenoids in the transmission to do the actual shifting.
It's more likely the TCU is being fed bad input from a sensor (particularly since the OP reports idle issues too) or can't operate the solenoids properly than it is the TCU itself has failed...but failures do occur. Certainly check the TCU fuse.

I'd then check TPS operation:
Key ON, engine OFF.
There are three wires to the TPS: +5V power, Ground and Signal Out.
The Orange/blue tracer should be the Signal Out. Backprobe that wire with a multimeter, the your other test lead to Ground.
You should see nearly 0 volts with the throttle closed, increasing to just under 5 volts as you rotate the throttle wide open. The increase should be smooth with no flat spots or drop outs.

And then check the wiring from the TCU to the transmission solenoids. OP did say they hit some water? If water made it's way into any transmission connectors, dry them out.

Hoepfully AKXJJake will find the problem in one of those areas.