Pcm??

[NYChris]

Ever since I bought my truck a little over a year ago, I've had no grid heaters, no cruise (except once last summer) and no O/D. After reading the follow ups to CB's post on possible electrical problems I got thinking.



Could the lack of preheaters, CC, and O/D be a bad PCM? I attributed my O/D problem to the TPS, which interestingly enough I found out had been apart before. Is it really the problem though? I don't have voltage regulation problems though, that I know of. What is the KSB?



The truck starts and runs good and I've gotten by without the grid heaters and cruise, and have hotwired the O/D.



Just curious.....

 

[dpuckett]

Dont think..... that makes more smoke

The KSB is the strange looking appendage on the lower driver's side of the pump. it increases the low pressure internal pump pressure to increase the timing a little ~2deg if I remember correctly. THE cruise could be one of a few things- bad servo, out of adjustment, no power and/or vacuum to the servo. THe adjustment has a clip next to the throttle cable that can slip out, rendering the CC useless. THE grid heaters could be your realys, or again, power to them. I'm out of ideas, but someone else may have some. I guess it could be your PCM, but as it is the costliest thign involved, I'd check all the little stuff first.



Daniel

 

[Philip]

With all the electrical problem you listed. It sounds like its time do to some troubleshooting. Yours is the same year as mine.



The cruise controll has some weak switches from the factory. Do you hear a click when you try to set the cruise. Or do the switches feel mushey when you try to engage? Also check you vacuum switch mounted on the left side wheel well. It is just behind the hood hinge. If it is bad cruise will not work. Check the hose to it also. It has a spot that likes to rub over by the brake booster.



The grid heaters are controlled by your air intake temp sensor. It is mounted to the right of your main air intake tube from the intercooler. It is the first sensor there. If you need troubleshooting spec's for it let us know. This thread has some info on the grid heater trobleshooting.



https://www.turbodieselregister.com/forums/showthread.php?threadid=64402&highlight=air+intake+sensor

 

[1stgen4evr]

PCM

If the previous owner put a seperate voltage control on the alternator, you would not have a problem with that. If there is nothing on the alternator that is different, then you have voltage control from the PCM. You would know if you had a problem with voltage control as the battery would go dead.



None of this is proof that the PCM is good in all respects, or bad for that matter. That will require considerably testing. If you make all the stuff work that doesn't now, put in a post to advise what you found. Others have the same sort of problems. Myself included. My solution is to put an 89 wireing harness on the rig. No PCM, No TPS, Old style voltage regulator, OD on the shift handle, Press to run type switch for the grid heaters. To name a few.



1stgen4evr

James

 

[paccool]

Does the air conditioner work? The PCM controls the CC, Air conditioner, Alternator, and a few other things. My sons 92 went out and he had to put a manual voltage regulator on the truck to keep going until the PCM could be ordered.



FYI- The PCM has been reported to be $700 or so. That is not correct. I bought one for my son at the local Dodge dealer. Was a rebuilt unit but had Dodge name on it. It looked like a brand new unit. The cost was just a little over $200 plus a $75 core charge on the old unit. Plus tax on the entire thing. I get a decent price from the dealer but I'm sure a few of you could beat that price. The dealer my son talked to wanted $275 plus core and tax. The local cheapy auto parts where my boy lived wanted $325 or something close to that.



Stan

 

[NYChris]

I don't think anything has been changed as far as the alternator goes, and the A/C does work. So those two things point to a working PCM. It's looking more like I've got a bunch of problems, sensors, relays, etc. , knocking out several accesories. There seems to be a lot of non-factory wiring on the driver's side fender well. Who ever rigged up the trailer wiring and brake controller really hacked things up. I wonder if any of that mess is contributing to my problems.



Guess I better get out the meter and some wiring diagrams. BTW, I got my service manual yesterday, brand new from Chrysler. What a book! It will definitely be worth the investment.



I'll keep you posted with any progress and will likely be back with questions.



Chris