New to the forums did some browsing & got some questions answered (thanks!) but still have issues.
2003 WJ 4.0 laredo. Got it used in 2007 now has 152,XXX on it.
Problem: CEL came on about a month ago w/ codes P0122 & P0123. Replaced the TPS & cleaned out the throttle body at the same time. Worked fine for all of a week then the same codes came on. Part came w/ a 2 year warranty so I returned it & replaced w/ new one & same thing.
95% of the time there is no problem. Other times the throttle will surge when cruising, but not during idle or acceleration. Surging happens when I go over a bump (RR tracks) sometimes and it needs more gas when in reverse or it will die out.
Figured it's a wiring issue, but played around with the wires at the throttle body and nothing changed with the idle until I had completely unplugged it. I do not have a voltmeter so I cannot comment on that, yet. This is where I'm at now, stuck.
I have a 2003 GC 4.0. Had problems last year with "hicupping" When I would go over bumps the speedo and tach would drop and then pop up. It would die when I shifted into reverse. Can't remember the codes I got, but I replaced the CPS, TPS, fuel pump, air idle control, O2 sensor. Finally unplugged the PCM and replugged it plugged it back in, and the problems went away. Do a search on how to do this properly. Hope this works for you.
I checked it out w/ a voltmeter & indeed the voltage was low (followed the guidelines in the Haynes book, voltmeter read 1.8)
Was still having problems & brought it to the dealer (at my wits ends) for them to check it out. They ran it through diagnostics (which only told them what I already knew) and then they said I had a bad TPS connector and they replaced it. They drove it & everything checked out fine.
I drove it to run some errands and it was fine on the highway (about 20 miles) and then, when sitting at an off ramp the CEL came back on w/ code P0122, but there was no issues with it running rough. On the way back home it began the surging while cruising issue again and I'm back at square one.
It is going down the same path as when I followed nicksmama suggestion. It will get progressively worse & over time it will begin to throw code p0123. Hoping not a PCM, but I don't know where else to turn right now.
Check the connections on the PCM also check the soldier joints inside the PCM. If you are a decent soldierer, or know someone who is, they can be fixed. It would be my guess that a capacitor came loose in the PCM. Fairly common problem.
2002 Overland - 4.7 HO, "Select-Drive", 4" RC long arms, TAG front winch bumper, 32" BFG KM's, 3" exhaust, Magnaflow hi-flow cat, Flowmaster 50 series
How are you checking the tps with the voltmeter?you need to check the sweep, not the voltage at one position.
At idle it should be .4-.8v and at WOT it should be about 4.5v. The voltage should increase smoothly from idle to wot with no dips or spikes. Sounds like you're not using a OEM sensor to me though and it's bad.
'97 zj 5.2, some stuff, some other suff, and some things that even work sometimes.
I was following the Hayne's book. I don't have it in front of me in the moment, but the directions told me to test the voltage at the connector w/ it unplugged and the key turned to on, but with the engine off. Voltage should be around 5.0 at this point. That's what I did and I got a reading of 1.8.
I misplaced my pins to back-probe it, so I haven't gotten the chance to try the sweep, but if it's low right from the get-go & unplugged would it really be the tps? This is why I'm stumped.
"3 Before checking the throttle position sensor, check the voltage supply and ground circuits from the PCM. Disconnect the electrical connector from the TPS. On all except 4.7L V8 models, connect the positive lead of a voltmeter to terminal number three and the negative lead to terminal number one of the harness connector... Turn the ignition key On - the voltage should read approximately 5.0 volts. If the voltage is incorrect, check the wiring from the TPS to the PCM. If the circuits are good, have the PCM checked at a dealer service department or other properly equipped repair facility."
Myself not being a master repair technician, I followed the above instructions and got a reading of 1.8 volts. This just so happens to coincide with the P0122 code - TPS voltage low. So, again not being a master repair technician, my thought is "crap in, crap out". If it's low before getting to the TPS, I'm led down the path it's not the TPS. And this is where I'm at now.
Not yet. The connections to the PCM are good, but there is no way I'm going to open it up and take a look in there. I'm hoping it's not the PCM, but I don't really know where else to turn other than throwing money at it and replacing parts at will (MAP, IAC, anything else with the word "sensor" at the end, etc.). Probably going to end up back at the dealer and out of my hair. Another thought is that the PCM just needs to re-flashed(?).
I was just wondering if you ever found out what this was? I thought we solved the problem on my Jeep, but after 13 months it started doing it again. Needless to say, we are at a loss of what it could be. It is at the shop now and the mechanic says he wants to, at a cost of $550.00, replace all (4) oxygen sensors. However there is no check engine light so, even he agrees, that this may not be the problem. Any help would be greatly appreciated.
Thanks for bringing this back up, forgot to post the good news!
It has been fixed, but not after some digging. What ended up happening is that the wires from the PCM to the TPS were routed through too hot of an area and had their coatings melted together and that was causing the problem. New wires & moved to a less heat-prone place has fixed things.