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BAH!!! Diagnostic code 45 IS BACK! #$&@(#)*&$)@(#


 
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Mad Scotsman
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Joined: 08 Jun 2007
Location: Golden, Colorado

PostPosted: Thu Jun 21, 2007 6:19 pm    Post subject: BAH!!! Diagnostic code 45 IS BACK! #$&@(#)*&$)@(# Reply with quote

Ok well I thought I had this TCC lockup solenoid issue licked the other week. Well, wouldn't you know it... the dreaded code 45 came up again (P0700 & P0743). These codes indicate an electrical fault in the TCC lockup circuit. I already replaced the TCC lockup solenoid (#3) with a brand new replacement. Got the luxury of driving the XJ for a week with no MIL lit up. However, I was still wasn't sure I was getting TC lockup despite absence of the check engine light. Here are the symptoms I noticed:

Note this is an AW4 automatic. Start up cold, put in gear & drive. Shifts through all 4 gears and then the TC locks up. Cruising down the highway at 70mph @ ~2300rpms. Lockup is working fine. Engine is warmed up now. Tap the brakes to unlock the TC. TC unlocks. Foot off the brake and back on gas. NO TC LOCKUP NOW! It now takes ~2500rpms+ to pull 70mph. Obviously the TC lockup is not working now. Still no check engine light. That takes about 15-20 minutes to come on. Once on I get the code 45 (P0700 & P0743) again. S.O.B.!!! As an additional note I replaced my TCU with a known good unit in case there was a problem with my original TCU. I still get this error code.

Now, here are my thoughts and I'd like some input from the experts here. According to the FSM TC lockup is dependent upon input from both the TPS and the brake switch. If I understand correctly TPS input voltage lets the TCU know when to lock up the TC. The brake switch tells the TCU when to unlock the TC. I would assume that if either one of these signals is out of range and/or erratic it could cause TC lockup to fail. Certainly a TPS with a dead spot could possibly cause this issue? The only thing that concerns me with that theory is there is no TPS code. Is it possible for a TPS to have a dead spot, thus killing input voltage to the TCU, without the TPS actually throwing a code? I'm really stumped on this one. I have already conducted partial tests on the TCC solenoid circuit to ensure there are no opens or dead shorts. So far I find no faults in the physical wiring so I am led to believe that the TCC lockup code is being tripped by an erratic or out-of-range input signal that's not being picked up by the ECU from either the TPS or brake switch.

Thoughts? Suggestions? I hate to keep throwing money at this issue hoping something will fix it. This one has me beating my head against the wall.

Thanks!
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dancerman
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Joined: 08 Jun 2006
Location: Atlanta

PostPosted: Fri Jun 22, 2007 2:38 am    Post subject: Reply with quote

Why can't things be simple anymore? I am most certainly not an expert but I'm just wondering if anything mechanical can be the source of the results?
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Mad Scotsman
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Joined: 08 Jun 2007
Location: Golden, Colorado

PostPosted: Fri Jun 22, 2007 7:38 am    Post subject: Reply with quote

dancerman wrote:
Why can't things be simple anymore? I am most certainly not an expert but I'm just wondering if anything mechanical can be the source of the results?


Simple? Not exactly synonymous with the modern computerized vehicle. I long for the good 'ol days when you looked for spark & fuel. Crying or Very sad

As for the root cause, well the codes I am getting are "electrical". However at this point I'm not ruling anything out. I am troubleshooting the circuit for an electrical fault thinking this could be an elusive and intermittent electrical gremlin. Neutral If I cannot absolutely find anything electrical then I will start suspecting a mechanical root cause i.e. torque converter, valve body, etc. All I know is this one is making me nutz! pull hair
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ThePhantum
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PostPosted: Fri Jun 22, 2007 8:52 am    Post subject: Reply with quote

I'm too lazy to look it up in my FSM...but if that is correct and the TCU is taking it's inputs from the TPS to lockup and from the brake switch to unlock...and if both the TCU and TCC solenoid are known good, then it's either the TPS or brake switch.

I will say this, there are LOTS of problems that can be caused by a bad TPS that will not trip a TPS related trouble code. I think your best bet it to replace the TPS.

Just my opinion...
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Mad Scotsman
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Joined: 08 Jun 2007
Location: Golden, Colorado

PostPosted: Fri Jun 22, 2007 11:55 am    Post subject: Reply with quote

ThePhantum wrote:
I'm too lazy to look it up in my FSM...but if that is correct and the TCU is taking it's inputs from the TPS to lockup and from the brake switch to unlock...and if both the TCU and TCC solenoid are known good, then it's either the TPS or brake switch.

I will say this, there are LOTS of problems that can be caused by a bad TPS that will not trip a TPS related trouble code. I think your best bet it to replace the TPS.

Just my opinion...


Yeah, this one is really puzzling. I am going to do a thorough inspection of the wiring and all segments with a volt/ohm meter so I can eliminate opens/shorts in the wiring. If that all checks out then I will try a new TPS. I measured the TPS and it would seem to be functioning correctly but I don't know if I have an intermittent heat related problem with it or what. What I do know is this is a frustrating problem. I don't want to resort to taking this to a dealer because I'm thinking they will have less of a clue than I do at this point. Rolling Eyes
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ThePhantum
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PostPosted: Fri Jun 22, 2007 3:18 pm    Post subject: Reply with quote

I know this is kind of off topic, but it does illustrate just how goofy these sensors are.

I had a problem about a year ago with the Jeep hesitating. It would only do it at highway speeds with gentle increases in throttle and it was extremely intermittent. I was chasing that gremlin for about a month, testing every sensor, checking wiring...nothing. Then, it started just randomly stalling at slower speeds as well. It would always restart and I never got a check engine light or a single trouble code.

I ended up replacing the Crank Position Sensor on a hunch. *POOF* problem solved.

By all means, eliminate the possibilities by checking for open/shorts, etc. But, depending on how many miles are on the Jeep, it probably wouldn't hurt to replace the TPS anyway. Besides it will also give you an opportunity to clean the throttle body and IAC sensor while your at it. Wink
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Mad Scotsman
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Joined: 08 Jun 2007
Location: Golden, Colorado

PostPosted: Fri Jun 22, 2007 3:47 pm    Post subject: Reply with quote

ThePhantum wrote:
I know this is kind of off topic, but it does illustrate just how goofy these sensors are.

I had a problem about a year ago with the Jeep hesitating. It would only do it at highway speeds with gentle increases in throttle and it was extremely intermittent. I was chasing that gremlin for about a month, testing every sensor, checking wiring...nothing. Then, it started just randomly stalling at slower speeds as well. It would always restart and I never got a check engine light or a single trouble code.

I ended up replacing the Crank Position Sensor on a hunch. *POOF* problem solved.

By all means, eliminate the possibilities by checking for open/shorts, etc. But, depending on how many miles are on the Jeep, it probably wouldn't hurt to replace the TPS anyway. Besides it will also give you an opportunity to clean the throttle body and IAC sensor while your at it. Wink


Well, my Jeep is a 97 Cherokee with 141,000 miles on it. I just picked it up a couple of weeks ago so I have no idea when or if the TPS has ever been replaced. I guess it's worth a try. My volt meter indicates it works normally but I realize that could be really misleading. Like I said, who knows what it does at operating temperature. I've only measured it after it cools off a bit. It could have a very narrow dead spot or God knows what. I just don't know what else it could possibly be besides a faulty input to the TCU or a physical problem somewhere in the wiring. TCC solenoid ohms out normally. TCC solenoid circuit from TCU to 6-way connector in engine compartment has continuity. TCC circuit from 6-way connector to ground strap in engine compartment shows normal resistance for TCC solenoid. I'm pretty sure that's it as far as the TCC solenoid circuit is concerned. Of course if the brake light switch input has some kind of weird short to voltage and is still maintaining even a slight current when it should have none, I'm guessing the TCU could read that as a short in the TCC solenoid circuit. If the same thing is happening to the TPS input circuit then the TCU might be seeing an unexpected high/low voltage in that circuit and interpret that as a short and/or open in the TCC solenoid circuit. Damned if I know... guess the only way is to see what my meters tell me and go from there.
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Mad Scotsman
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Location: Golden, Colorado

PostPosted: Sun Jun 24, 2007 2:49 pm    Post subject: Reply with quote

Well, I replaced the TPS and brake switch both. I haven't gotten another check engine light yet but I also don't think the torque converter is locking. The torque converter will lock when I first start driving but then it stops locking once the vehicle has been driven a couple of miles. I'm really not certain at this point. I'm beginning to wonder if I have a two-fold problem here. I may very well have had a check engine light tripping the code 45 because of a faulty TPS and/or faulty brake switch. However, I wonder if the lockup clutch is just worn out too? I didn't find any large particles in the tranny when I changed the fluid & filter but there was definitely this thin layer of blackish looking small particles on the bottom of the tranny pan (I would think that is normal with 141k?). Anyway, since the lockup seems to stop working after a few miles that makes me wonder if the lockup clutch is just shot. I guess it could be shot if the Jeep was used to tow a lot in the past but I have no idea on the history. I guess if I don't get any more code 45 but I continue to get no lockup then I have to conclude it's the lockup clutch is shot. Rolling Eyes
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JeepinNH
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Joined: 13 Sep 2005
Location: New Hampshire

PostPosted: Tue Jun 26, 2007 6:44 am    Post subject: Reply with quote

Makes you wonder if the tranny oil was ever changed before you got the Jeep. Now it has new oil that may be removing any deposits the old oil had left alone making things sloppy in there. Just a thought.
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Mad Scotsman
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Joined: 08 Jun 2007
Location: Golden, Colorado

PostPosted: Tue Jun 26, 2007 8:26 am    Post subject: Reply with quote

JeepinNH wrote:
Makes you wonder if the tranny oil was ever changed before you got the Jeep. Now it has new oil that may be removing any deposits the old oil had left alone making things sloppy in there. Just a thought.


Yeah, it looked as if it had been changed at least once before I bought it but yes, you have a very good point there! A trans fluid change, new TCC solenoid, new TPS, new brake light switch, wiring inspection and still no lockup (unless I missed a wiring issue somewhere?). I have only to conclude it's an internal issue with the tranny. I will probably go ahead and dissect, inspect, and rebuild the valve body next. It probably needs it anyway and could possibly fix my problem.
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