Error Codes

[Can1991Ram]

My 1991 Ram 50 2.4 Auto 2WD started throwing codes..

I remember someone saying that some of these could be related to a ground issue?

Code 15 - Motor Position Sensor
Code 21 - Engine Coolant Sensor
Code 25 - Barometric Pressure Sensor
Code 13 - Intake Air temp

The truck is tough to start and has a rough Idle.

Any help would be appreciated.

The air flow sensor was changed with a remain last year where the air temp sensor is..

[Can1991Ram]

I pulled the ECM and it has been swapped once before. You can see the markings from a Junk Yard. the ECM was from a 93 D50

The electrolytic Capacitors look great.. nothing budging... The ECM was MD163056

[Can1991Ram]

I took the ECM out into the bright light and one of the electrolytic caps leaked and ate 2 tracers. So.. that is the source of my issues.

I could only find 2 used ECM's for my truck in all of Canada, but I bet they would need recapping.

A new reman ECM in Canada for this track is close to $500!!

For twice that I could put a Holley Sniper on the truck using the spare carb intake I have... grrrr

[Can1991Ram]

I feel like I'm talking to myself.... but I found a reman ECM out of a wrecked truck in the US for considerably less that a new reman.

I hope this works.

[pennyman1]

It is tough to help with ECMs for these trucks - they disappear quickly. Goodluck with the new one!

[Can1991Ram]

I have a friend that is great with electronics. We are going to recap the one I have and install bodge wires to connect the broken traces. I will keep it as a spare.

One of the issues I think is the fact that the factory only put 16 Volt caps in. I'm going to recap with 50 volt caps with a much higher heat range than the 100 C heat range that is factory.

I'm going to check the continuity when I'm done and look for other dead caps that aren't electrolytic.

I'm going to look for an e-prom (supposedly available after 94) computer and see what the big difference is.

As soon as this "reman" ecm comes in I'm going to check the caps and recap if necessary again if needed.

[StarquestMan]

just spotted this thread and thought i might add if you haven't already ordered the capacitors yet, make sure you use name brand ones like Nichicon or Nippon Chemicon cause the no name brands are hit or miss quality and their ratings are often useless. im not sure what kind of electronics suppliers are up in Canada but im sure some should carry some good brands. I have recapped things with cheaper caps from variety packs etc only to have them crap out again later. heck ive had more luck pulling 30+ year old used nichicons and using them over brands like capxon (craps-on)etc.

[Can1991Ram]

I'm really leaning towards putting in ceramic caps in place of the electrolytic

[geezer101]

The ceramics appear to be the way to go. Way more stable when exposed to heat. If they aren't expected to hold big loads they will maintain their storage output. Age doesn't seem to impact on their performance either. Hopefully the only reason electrolytic caps were used was cost and not something like noise suppression.

[Can1991Ram]

Well.. I got the used reman today and it fixed the issues. It still had the seal on it from 2002 so I cracked it open to have a look. This ECM was a mess to fix. This laid down solder to replace the traces, put an electrolytic and a ceramic in serial to get the 100uf they needed for the one capacitor value.

But... it works and the truck is actually idling better and smoother than before so I suppose the caps have been an issue in mine for a while.

The ECM I have has a board in WAY better shape than this one was so mine should be easy to fix for a replacement.

The nasty thing is cleaning the conformal coating off to get to the copper.

If I can figure out a way to post a picture I have a side by side of an original this repaired one.

[Can1991Ram]

22429
The left is the original, the right is the reman from 2002.

[Can1991Ram]

Now that I look at it. The reman only has 2 of the 4 caps replaced.... I would have thought they would replace all of them since 2 leaked.

I'm lucky that only 1 leaked on mine. I will have to do a continuity test on some of the traces on mine.

It also looks like they reflowed the bottom of the board as all of the through holes are filled with solder on the reman one

[Can1991Ram]

The ceramics appear to be the way to go. Way more stable when exposed to heat. If they aren't expected to hold big loads they will maintain their storage output. Age doesn't seem to impact on their performance either. Hopefully the only reason electrolytic caps were used was cost and not something like noise suppression.

From what I read, the ceramics aren't available around the 100uf value.. I could be wrong. You can see on my reman they used both the acheive the 100uf value ( or that's all they had on hand for the repair).

Electrolytics are terrible in the heat.. your correct. If haven't been able to find a schematic but it looks like the capacitor that failed on mine could be for smoothing the input 12v from the alternator. That could be why it's rated to 105C and 16V,, lots of heat cycles and it gave up the ghost. This would be the third computer in this truck since 1991.

On the advise of a friend, I will be replacing my caps with tantalum caps. There is only 4 so the cost isn't that great.

[Can1991Ram]

Well.. went for the first drive since last September. Starts right up.. no trouble codes and still as gutless as before. Still driving around in OD at 50 mph at 6 to 10 inches of vacuum to maintain the speed. This motor is TIRED out. But... it is running and driving so thats a start.

22442

[geezer101]

Try retuning the ignition timing. Hold it @ 2000 rpm and swing the distributor between retard/advance til you get an rpm increase then lock it up. I would also under gap your plugs by 0.05-0.15mm and try using a premium fuel. You should find some extra throttle response and faster upshifts.

[geezer101]

Oh, I just had a look at the ECM board pics. Nasty...:shock:

[Can1991Ram]

I will post a pic when I fix my original ( which itself is a junkyard replacement).

[pennyman1]

Tantalum caps have their good points and bad - they may work in the ECM, or cause strange problems. They will clean up the voltage going across them, so that is a good point. Used to use them in coin-op games to solve weird problems with noise on the circuit boards.

[claych]

^^^edit!!!
APOLOGIES PENNYMAN, wrong thread!!!