WJman

Just replaced the alternator on my WJ (2000), another electical problem. It is still overcharging above 16 volts. No codes on on board diagnostic, dashboard insruments odometer flashes and goes out, cannot adjust dimmer on this either, other dash warning lights stay on (brakes/ABS), prior to this six months ago, replaced a tension pulley (fixed not adjustable) as bearing was bad and blew out CD player and at times shorted out entire engine/dash lights.....I know regulator is in PCM, can this be replaced or by passed! HELP!

dave1123

IDK if this has anything to do with your problem, but underneath the battery is a temperature sensor that tells the PCM to cut back the charge rate when the battery starts getting hot. This sensor may be faulty or shorted.

WJman

Cut back the charge rate? Will that give me the 16-17 volts on the meter also? But I get no fault codes or check engine lights.. How can I test the sensor? Thanks for replying

fishbone

This is almost 100% a voltage regulator issue. As you already know it's incorporated into the PCM. Have you tried re-setting the PCM memory by clearing out the KAM? Just a long shot but simple and worth a try.

WJman

Don't have obdII reader or program capabilities? What is KAM? Can I buy a after market regulator and by pass PCM? Will this also cure the dash problems to go away? Sounds like a dealer$hip visit to me......

fishbone

If you do a search on the net, you'll get several results on how to do this. I've seen folks say, disconnect both battery terminals and leave off for an hour, disconnect only the negative and leave off for 2 hours....etc. Essentially what you are attempting to do is discharge all the stored electricity from the capacitors on the PCM (KAM, keep alive memory). The purpose of the KAM is to maintain learned values about your vehicles performance for the PCM to reference such as shift point, throttle position, long term fuel trim...etc. In theory, the stored electricity will dissipate over time once you remove the power source, ie: the battery. However, there is no guarantee that this will happen over those periods of time unless you have given the stored energy a clear path to ground, so I say those procedures are flawed. I will admit that I am not certain about the relationship the voltage regulator plays with the PCM, so doing this maybe a total waste of time but, if you are interested in trying it, let me know and I'll post up a procedure on how to this, the way it was taught to me. Ultimately, I believe you have a bad solder trace somewhere on the pcm board (as Chrysler is notorious for this) and it will have to be replaced. I think there is a secondary board inside the PCM that connects to main board through a pin connector and likely one of those solder traces is bad.

WJman

Had battery off for a week, so that theory didn't work, so will need to replace the PCM. Can I take it if vehicle and just bring PCM to dealer$hip for repair and reprogramming only? Strange about dash going haywire at one or 2 times static over speakers like it was huge short happening. Just hope all goes back to normal after charging returns to within parameters.

fishbone

No dealership I'm aware of will make repairs to the pcm. Perhaps if you have an electronics guy in the area, he can repair. If you have the skills to pull the pcm, then you will have no problem replacing it. If you can find a new one, you'll give them your VIN # and vehicle details and it should already come pre programmed with the latest software and flash programming for your specific model. Other than a brief relearn procedure prior to start up, after start up and during initial run, it will essentially be plug and play.

Shop it around if you plan on replacing it. Here are just a few examples I found online:

http://store.allcomputerresources.co...m-pcm9906.html

http://www.solopcms.com/1999-thru-20...okee-4-7l.html

https://www.autocomputerexchange.com...type=200&price[from]=&price[to]=&search=

WJman

Thanks for the help----the other problem (not really), is I am living in Sweden (retired Marine), have a European Jeep (made in Austria)....I contacted the dealership and yes, they were confused about repairing the PCM! Can I match a used one from a junk yard? Does US PCM good in Europe Jeep? You say plug and play, that is automatic internally in the jeep correct? Is it better to buy a aftermarket Voltage Regulator (US $50), if so, will PCM work properly?
Had same problem with a mazda years back, got used PCM and it worked OK, but am sure dealer would have to install and reprogram it or monitor instalation! Will contact US websites and given them my VIN# and see what it brings!

fishbone

Ahhhh! These questions are a little over my head. Sounds like you need to do some more research on that euro jeep. Do you have any electronics techs in your area? A tv repair guy? Perhaps if you pull the pcm and ask them to check the PCM for bad solder traces and bulged capacitors, they will do it for you. As for getting one from a scrap yard......ehhh, I wouldn't. Never know what kinds of problems you would inherit. As for the plug and play comment I made, yes it will be pre-programmed, all you would do is install it. Then you go through a brief, period for the new pcm to re-learn the correct parameters on your Jeep. It simply involves, allowing the Jeep to sit for about 1 min with key on engine off (to learn stop values), then start engine, let run until it comes up to operating temp or close to it, then you take the shifter through all the gear positions allowing a stop for several seconds in each position from P down to 1 and then back up to P stopping again for a few seconds in each position. Then take Jeep for a ride taking care to accelerate slowly and evenly for the first several miles then you are done. Nothing more is needed.

Replacing the PCM is somewhat a large expense as you can see from the links I provided. Possibly even larger for you, if you can even find one. While I'm 99% sure this is a regulator issue please make sure you have done your diligence by checking all other components before replacing the PCM. If the alternator is good but the regulator is not knocking down the voltage to levels around or below 14V while charging, that is the reason you are seeing all the crazy things with the dash lights and the radio. The voltage readings you have are damaging to these electronics components as you already know by blowing out the radio/cd player. You should get this fixed asap.

WJman

You are a genius! Must be PCM as installed 2 alternators with same voltage output of 16-18 volts (16.8-17.4). Will see what the local jeep merchant says. Will also mail my vin# to your links to see what they say also. Strange I am getting no codes on inboard diagnostics? Keep u posted. Thanks again

czettlera

Hi just an idea before ordering the pcm. You should check the wiring between the pcm an the generator. There can be a broken cable, and cause the same problem. Other: If you turn all the head lights on, does the other problems with the dash and the radio disappear? Normally the voltage should fall down a little bit, in this case.

fishbone

That's a great idea CZ. And that's what I meant by saying to make sure you do your diligence and check out everything else before jumping into a pcm replacement. Dave mentioned earlier in this post about a battery temperature sensor and honestly I had no idea of this component but certainly worth checking out. It is also possible that something such as a short has fried that section of the pcm. While my experience with voltage regulator integrated with the pcm is somewhat limited, my past experience with voltage regulators in general tells me that every time the voltage has presented itself on the high side, it indicated a faulty voltage regulator.

Good Luck and let us know how it turns out.

WJman

Hi, turn lights on odometer goes out completely and can't adjust dimness. If was bat temp sensor I would get a code in diagnostic., funny though at times things are normal in dash (except dimming)."will check all wires to from alternator, waiting on local jeep they seem stumped!

WJman

Normal but still overcharging!