Hey folks. I've been drilling down on possible causes for my recent hard start and weird idle issues on the old 96er ('96 4.0 Cherokee), and it seems like I'm finally getting some traction. After replacing my throttle position sensor with OEM and cleaning my idle air control valve I'm still having issues, so I hooked up the old OBD reader (even though no CEL is on) and lo and behold I've got 3 codes. Wish I knew this earlier...

P0505 - IAC system malfunction

P0123 - TPS high voltage

P0118 - engine coolant temp high voltage



The chatgpt says all 3 are probably due to a shared electrical issue or sensor reference problem (whatever that is) as opposed to 3 different causes.

It ranks the most likely causes as...

1) bad sensor ground

2) short to voltage on the 5v reference line

3) wiring harness damage near throttle body


I can unwrap and check all the wiring harnesses for wear damage or inline shorts, but I'm not too sure about checking the ground connections at the engine and firewall as chatbot suggests.


Where do I find these connections please? All advice appreciated.

 

I would advise to stop using chatgpt, get a factory service manual and troubleshooting guide. Check out www.charm.li
Going through proper diag is better than having some canned response from some clanker.

 

I'm looking at the 1997 schematics. IAC goes to


while TPS and coolant sensor are grounded to the K167 circuit (which basically is the ground for everything else and seems to me you'd have tons of other codes).

I do like the idea that it's something near the throttle body harness.

 

Maybe start out by seeing if the other 2 sensors are getting 5V from PCM: