Need XJ Cherokee diagnostic help.

Need to bounce some ideas off the hive. 

Alright, need some help. Got P0122, p0700. 

New clock spring, clean grounds, good battery, new good tested tps, runs a drives fine, light just drives me nuts. 

Pulled horn fuse, light comes right back on for those codes.

Unplugged clock spring, light comes right back on. 

Thoughts? Ideas? 

Was thinking is might be a dying ecu or tcu but don't wanna spend the money if I'm overlooking something dumb. 

P0122: The TPS sensor is on the bottom of the throttle body.  Should be a 3 pin white plug.  Check the connection, or replace sensor.  They may be pricey.

P0700: Check the battery terminal connections, and cable condition.  I think there are 2 plugs by the dipstick tube that have do with the transmission and transfer case. Check and clean them up.

Hopefully this helps, and resolves the issues.

Thankfully my '99 XJ hasn't had these.  My problems were with the EVAP.

Dirtydog (Forum Supporter) said:

P0122: The TPS sensor is on the bottom of the throttle body.  Should be a 3 pin white plug.  Check the connection, or replace sensor.  They may be pricey.

P0700: Check the battery terminal connections, and cable condition.  I think there are 2 plugs by the dipstick tube that have do with the transmission and transfer case. Check and clean them up.

Hopefully this helps, and resolves the issues.

Thankfully my '99 XJ hasn't had these.  My problems were with the EVAP.

Tps sensor is new, and known good and checked voltage at sensor.

Connectors are clean and have good connection for the transmission wiring. 

Hmm.  Knock on wood, never had these issues.  What condition are the battery cables in?  Sometimes they corrode inside out. I know you checked for grounds, but.... I don't know enough about it, but i don't get how steering wheel stuff is associated.  May be time to look at a wiring diagram, or access to good scanner to check the computer crap.  Sorry I couldn't help further.

Just a thought.  I believe P0700 is related to the transmission and transfer case.  Would fluid levels have anything to do with it?  Just spit balling here.

Dirtydog (Forum Supporter) said:

Hmm.  Knock on wood, never had these issues.  What condition are the battery cables in?  Sometimes they corrode inside out. I know you checked for grounds, but.... I don't know enough about it, but i don't get how steering wheel stuff is associated.  May be time to look at a wiring diagram, or access to good scanner to check the computer crap.  Sorry I couldn't help further.

The whole battery cables are new as of November. Had the snapon solus  hooked up and drove it around looking at data. Basically soon as it's started up codes popped. Tps voltage is within range, transmission shifts find and only throws a general code. 

Dirtydog (Forum Supporter) said:

Just a thought.  I believe P0700 is related to the transmission and transfer case.  Would fluid levels have anything to do with it?  Just spit balling here.

Fluid is pretty new in both and full, double checked that. I think next step is going over harness with a fine tooth comb. 

For the TPS, confirm the connector itself is good and making good contact.  I've seen quite a few cases on OBDII ZJs where the TPS connector was the issue, not the TPS itself. 

From what I can find, P0700 means that the PCM (ECU) is complaining about the TCM misbehaving in some way.  But it's not a very specific code, and I'm not sure if there's a way to directly scan the TCM (probably requires a fancier scan tool).  There's no PCM connected elecronics on the transfer case beyond the vehicle speed sensor, so that can be ruled out as a problem. 

If you haven't done this yet, pull the connectors at the PCM and check them over, make sure they're clean and well seated.  I once saw a PCM connector get all oily when an oil pressure sender failed internally and pumped oil through the wire back to the PCM, where it started leaking out of the connector. 

rslifkin said:

For the TPS, confirm the connector itself is good and making good contact.  I've seen quite a few cases on OBDII ZJs where the TPS connector was the issue, not the TPS itself. 

From what I can find, P0700 means that the PCM (ECU) is complaining about the TCM misbehaving in some way.  But it's not a very specific code, and I'm not sure if there's a way to directly scan the TCM (probably requires a fancier scan tool).  There's no PCM connected elecronics on the transfer case beyond the vehicle speed sensor, so that can be ruled out as a problem. 

If you haven't done this yet, pull the connectors at the PCM and check them over, make sure they're clean and well seated.  I once saw a PCM connector get all oily when an oil pressure sender failed internally and pumped oil through the wire back to the PCM, where it started leaking out of the connector. 

Tps connector is in good shape. Have a nice scanner and scanned TCM and have no faults and saw nothing alarming. Checked ecu and TCM connectors and cleaned them. 

Got a junkyard ecu, flashed vin with a drbIII and we are back in business. 

Professor_Brap (Forum Supporter) said:

Got a junkyard ecu, flashed vin with a drbIII and we are back in business. 

Perfect.  JTEC PCMs defintiely seem to develop some issues with age.  I've killed 3 in my ZJ.  One blown fuel injector driver, one blown coil driver (both happened on startup, the latter of course giving a no start).  And then one that worked fine until the engine bay got too hot, then it would flake out and cause weird behavior, stalling, etc. until you cooled the PCM down, when it would run fine again. 

Why do you need to flash the VIN to the ECU? I have a spare junkyard ECU for my XJ that I tested and it worked perfectly.

In reply to buzzboy :

Mostly because I could. 

buzzboy said:

Why do you need to flash the VIN to the ECU? I have a spare junkyard ECU for my XJ that I tested and it worked perfectly.

Functionally, you don't.  It only matters for a couple of scenarios.  If you've got emissions testing and they read the VIN from the PCM, they might care if it doesn't match.  And if you're using a tuner of any kind on it, putting in the correct VIN saves you from having to de-tune the old PCM, do a vehicle change, and re-tune the new one.  You can just flash the new one and the tuner won't care that it's not the same PCM.