I bought a reman pcm about 1.5 yrs ago. I think it's gone bad. Not sure why. I am in the process of finding out if the company will honor the warranty. If not, I am wondering where I can get a good pcm. Hopefully one that lasts longer than 1.5 years. Lol

Anyone have luck with any specific companies?

Thank in advance.

 

There is a company that does PCM's and such, that is a sponsor on this site. Check with them.

What makes you think your PCM is going bad?

 

HeyYou, thanks for the info. As to why I think my pcm might be the issue - I had p0303 code - see here for the thread.

Checked:
plugs, wires, fuel injector, fuel injector plug, dry compression at cyl 3 & 5, cap and rotor, and budget vacuum leak check with a propane tank

Replaced: plugs (since plug 3 was looking bad. It was the only one looking bad though), plug wires, crankshaft position sensor (looked bad and was right there), cap and rotor.

After I replaced those items, nothing changed. I unplugged the pcm to check connections and it looks fine. When I reinstalled it, the check engine light went away, but the vehicle ran more rough. Now it seem to run really rough around 40mph.

I did a fuel pressure check and bought a bluetooth obdII scanner. Fuel pressure with engine on but not running was 30. Engine running it was 48. Normal according to manual is 35-45. I couldn't find the fuel pressure regulator so I skipped testing that for now.

Vacuum according to the obd fluctuated between 16.9 -17.2 at idle. Normal according to manual is 17-22. Is the fluctuating normal? I dunno.

Not sure if fuel pressure and vacuum numbers are cause for concern.

After checking these things, I had a short spell where the engine woudn't turn over or it would die quickly while idling. I rechecked all the connections I messed with - plugs, injectors, intake, etc. Then I checked the pcm. After I checked it, the car started up again and held idle though the idle was rough. I figure disconnecting the pcm is why the check engine light went off. Now I can't get any codes even tough the van runs rough.

A couple of odd things I noticed. The tube that connects to the air box where the air filter is has no clamp? I've never seen a system where the air box and intake have no clamps on the tubes. Also the tube running from the valve cover to the air box also has no clamp by the air box. Again, I've never seen this before.

Anyways, with the way disconnecting the pcm is affecting the engine, it makes me think the pcm is bad. I mean I am still checking things, but the issues i had before I bought the reman pcm were idling issues and dying while idling. Now with the way it is idling, I am wondering if it could be the same. I plan on using a multimeter to check a few things, but I left it at a friends so...

 

What engine in your van? If you have one of the magnum motors, have you check the plenum? Have a look down the throttle body, (engine off....) see any oil down there?

Sure sounds like a vacuum leak to me. (vacuum is low, and fluctuating.)

 

I have a 5.9L v8 in a 99 ram van.

Thanks for the info. I was wondering if that fluctuating was a problem. I did a simple check of the plenum involving blocking off the pcv valve hose into the engine and disconnecting the crankcase breather hose and seeing if there is suction.


From this test, it doesn't seem like I have a plenum issue. Is that a reliable check?
I can look into the throttle, but it's a little difficult, that's why I did this test instead. I might be able to use a camera to look into the throttle.

My plan now is to replace plugs with copper ones. Try driving without the front o2 sensor. Replace o2 sensors since I have one sitting around from when I was unable to remove the sensor on the exhaust. Then I'll buy and replace the front sensor. Wiggle some wires and see if anything changes. Then if none of those produce results, bring it to a shop to get diagnosed. Maybe I'll try the propane vacuum check again since I have the obd to help check the rpms.

Should I try anything else?

Thanks in advance.

 

With PCV disabled, there should actually be pressure in the crank case.

 

Soooo, that's not a reliable test? I had some pressure outwards. Like when I removed my finger from the crankcase breather hose it was followed by a small puff of air coming out of the hose. Ok, well, i'll look into the throttle body today since I will be working there anyway.

I just drove the vehicle with the front o2 removed. The engine acted the same except the really rough vibrations came at a higher mph. This time at 55-60mph. What does this mean? I suppose the o2 is not really the culprit here?

Thanks again.

 

I usually disable pcv, (pull the hose from the valve to the manifold, plug both ends, pull the hose off the air box, plug that, and take off the oil fill cap.) Start the engine, and see whats what. There should be a noticeable breezed coming out the fill cap..... if you can barely feel it, or there is ANY vacuum there at all, plenum is likely bad.

 

Well here are some pics of the throttle... Looks dry to me, no?




Thanks again.

 

Yeah, that really doesn't look bad at all. I expect to see some in there, from the PCV system.