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Discussion Starter · #1 ·
My '97 Cherokee (4.0, auto trans) has a hard code that keeps the Check Engine light on.

The code is "45". I can find NO listing for code "45" in ANY manual or anywhere on the web, even after searching for hours. I can clear the code and get the light to go out by disconnecting the battery for several minutes. After hooking the battery back up and starting the engine, the light will stay off and everything's fine for about an hour or so - engine runs fine, A/C blows nice and cold, auto trans shifts fine, no issues whatsoever. After a while, though, the Check Engine light comes back on - code "45" again. Even with the Check Engine light on, there are no symptoms or problems - everything runs and works just fine.

I've checked and cleaned the battery connections, reseated the wiring plugs at the ECU, verified charging voltage (13v at the battery at idle with A/C on max, radiator fans blowing like crazy, high beams on, radio on, rear defroster on, emergency blinkers on, wipers on - basically as much load as I could put on the charging system, and still no voltage problem.

When I pull the codes, the only ones that show up are:

"12" - (battery disconnected) which makes sense because I disconnect the battery to clear the code 45

"45" - can't find an explanation for this code anywhere

"55" - end of code listing

What the hell is code "45", why does it keep coming back, and why do no symptoms show up when it does? Bad ECU, maybe?
 

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Discussion Starter · #3 ·
Huh. Guess I'll have to check that out.

Thanks - and where did you find that description? I looked everywhere I could think of - manuals, websites, etc.
 

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Also, for further reference. If you ever get a check engine light on, and does not affect the way the car runs, check the gas cap. I know most people know this by now, but just making sure. I do not know how many people come by my shop, and I run the code, and come up with: Leak in the evaporative emissions control, blah, blah. Anyways, when I have some time, I will go out and look to see what my manual says on the "45"
 

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Discussion Starter · #6 ·
Ok, I did some searching (through my service manual, on the web, and by crawling under the XJ and checking the trans) - apparently, '97 Cherokees with AW4 auto transmissions do not have transmission temperature sensors.

It's not mentioned, listed, or pictured anywhere in the manual, nothing on the web shows a trans temp sensor for a '97 Cherokee, and looking at the trans itself, I see the the VSS, the neutral safety switch, and a cable that has 2 wires going into the body of the trans (no plug or connector) - which I assume is the converter lockup clutch.

No trans temp sensor.

So......why does the computer keep coming up with a code 45 for a trans temp sensor voltage problem, when there's not even a temp sensor?

The trans has plenty of fluid. It's nice and clean. The trans shifts perfectly. I don't notice any weird smells or leaks coming from the trans area.

If there IS a trans temp sensor, where the heck is it, and why is it apparently such a big secret? I checked Autozone, Advance, Napa, O'Reilly's, and Pep Boys. NONE of them have a listing for a trans temp sensor for a '97 Jeep Cherokee.

I'm about ready to start unplugging shit until either the Check Engine Light goes out or the truck doesn't run.
 
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