Is the PCM repairable?

[saltedfish]

I got a woe Grand Caravan. Mechanic told me the PCM (Pulse Control Module), aka the CPU, need to be replaced. but the new part is too expensive. I am an Electronic Engineer and quite familiar with computer hardware, so just thinking if the PCM is repairable? any one have experience to share?

Thanks,

[Pete_Coach]

As an electronic engineer you must then know that in order to repair any of those computer devices you need access to the code, a test bench and the proper automatic test equipment and to be able to re-program it. Where do you think you would get that sort of equipment and access to the data?
In short, I would think you will not be able to fix it yourself.

[AGR-1]

The "electronic platform" of most vehicles is proprietary to the specific manufacturer, the customer becomes a "repair captive" to the manufacturer/franchised dealer.

Many manufacturers to save money give the franchise dealer the ability to "reflash" (upgrade the software/programming) of most modules.

If its a "hardware" issue there is no "rebuilt program" that rebuilds modules by returning a "core" similar to an alternator.

Right to Repair (http://www.righttorepair.org/)

[careener]

Have you looked for a used one?

[DrXenon]

I once took one apart on a motorcycle for which I couldn't find a replacement ECU. It turned out one of the capacitors was bulging so I replaced it and it was fine until I sold it 3 years later.

Unless it's something obvious like that, though, you're probably best off getting one at the wrecker's.

[stuntman]

People have mentioned used and rebuilt they are good options and are probably the most cost effective. New....forget it.

Looking for a used one one is a good advice. But, I would inspect it for issues with the water protection and repair b4 putting in (if required).

Your an electronic engineer. You best know your skill level and what is possible.

Access to code and proprietary test equipment for your one off fix? Sounds like a lot of bull, a lot of issues do not require that equipment or information. Having a schematic would certainly help maybe someone on another forum can provide one.

As an engineer you might know that the above items are often not required, but, it sounds like you have not had a lot of repair experience. Find a forum where someone actually fixed these items for the shortcuts and overview of how they are repaired.

sm

[stuntman]

i once took one apart on a motorcycle for which i couldn't find a replacement ecu. It turned out one of the capacitors was bulging so i replaced it and it was fine until i sold it 3 years later.

Unless it's something obvious like that, though, you're probably best off getting one at the wrecker's.

+1

[AGR-1]

On newer vehicles ECM's and other modules are coded for a specific serial number, finding a used one will not work, even if its from the same model vehicle.

Many of these black boxes are not interchangeable from one vehicle to another.

As an aside, most dealers will not take back a module as a parts return, you bought it, you own it.

[fastlayne]

If the van is still driveable, get a second opinion. The PCM (Powertrain Control Module) could be "failing" for any number of reasons, including loose or corroded connections.

[pitz]

Those boards typically have a conformal (ie: moisture-resistant) coating (http://en.wikipedia.org/wiki/Conformal_coating) as well. So even if you had the skills to do a PCB-level diagnosis and repair, removing the coating, without using nasty solvents, and equally important, replacing the coating, is problematic. (not to mention dangerous, as the solvents aren't products you really want to use without a proper fume hood).

The coating is to protect the board especially since temperature swings for auto electronics can be quite dramatic (ie: -50C up to +100C or higher, depending on application). Easy to get condensation forming and traces shorting if encapsulating coatings are not used.

Bottom line: get a used or rebuilt one. Unless you find a website that details a trivial fix. Other than that, stuntman pretty much hits the nails on their heads...

[l69norm]

I got a woe Grand Caravan. Mechanic told me the PCM (Pulse Control Module), aka the CPU, need to be replaced. but the new part is too expensive. I am an Electronic Engineer and quite familiar with computer hardware, so just thinking if the PCM is repairable? any one have experience to share?Thanks,

A lot of "PCM" problems in the Grand Caravan are actually wiring harness problems. Check the harness connectors for corrosion, especially the one inside the driver's side wheel well.

[Pete_Coach]

.....
Your an electronic engineer. You best know your skill level and what is possible.

Access to code and proprietary test equipment for your one off fix? Sounds like a lot of bull, a lot of issues do not require that equipment or information. Having a schematic would certainly help maybe someone on another forum can provide one.

As an engineer you might know that the above items are often not required, but, it sounds like you have not had a lot of repair experience. Find a forum where someone actually fixed these items for the shortcuts and overview of how they are repaired.

sm
Really? Do you think some of these components are even repairable? Without test equipment, test procedures and component requirements, would you use the main computer as the platform to test your repair of the component? Possibly ruining your main computer.
It is always easy to give advice if it does not affect your car.

[l69norm]

On newer vehicles ECM's and other modules are coded for a specific serial number, finding a used one will not work, even if its from the same model vehicle. Many of these black boxes are not interchangeable from one vehicle to another. As an aside, most dealers will not take back a module as a parts return, you bought it, you own it.

+1, some GMs are like this. Even the stereo will not work unless it's been programmed into the ECM with a scan tool.

ECM from the parts department are blank and also need to be programmed.

[stuntman]

Really? Do you think some of these components are even repairable? Without test equipment, test procedures and component requirements, would you use the main computer as the platform to test your repair of the component? Possibly ruining your main computer.
It is always easy to give advice if it does not affect your car.

Well, an earlier poster did it. So,yes these components are repairable.

The OP is an electronic engineer. Let him decide what he can an cannot tackle once he gets it open....I did.

Other things that qualify my statement:
I have repaired many types of electronic devices and in total have done hundreds of repairs.
I have an electronic technologist diploma and real world repair experience. I know how electronics work and generally what would be an would not be easily repairable in this situation. Basic components are very repairable.

The stuff is only magic voodoo if you are not educated in electronics....the OP is educated, let him make an educated deduction.

SM

[pitz]

Well, an earlier poster did it. So,yes these components are repairable.


But how do you deal with that conformal coating? How do you even identify what it is, and the solvent(s) needed to effectively remove it? Unless you remove it somehow, chances are, you won't even get to probe any of the pins (ie: the PSU section of the board).

Most often, on boards such as these, it is power supply failure, or instability, caused by component degradation. Power supplies not only operate in a harsh physical, but also harsh electrical environment, which often causes premature capacitor degradation.



The stuff is only magic voodoo if you are not educated in electronics....the OP is educated, let him make an educated deduction.


Sure... Pop that board out, see the conformal coating, and all the surface-mount 'stuff' underneath. Seal it all back up, and shell out for a replacement.

Expensive or not, surely an EE makes a good enough salary that they can afford a replacement ECU on their car, right?

[stuntman]

Sure... Pop that board out, see the conformal coating, and all the surface-mount 'stuff' underneath. Seal it all back up, and shell out for a replacement.

Expensive or not, surely an EE makes a good enough salary that they can afford a replacement ECU on their car, right?

Did you miss the my first line in this thread?

"People have mentioned used and rebuilt they are good options and are probably the most cost effective."

If he wants to do the work who are we to stop him. I don't know his financial situation, do you?

[DrXenon]

On mine, they used potting compound that came off easily because there were cracks I could exploit, and it was an easily-replaceable electrolytic capacitor, but I agree that many of these devices are not really economically repairable. I think it's mainly fine pitch surface mount stuff now.

As a fellow EE, you could always live my dream and install a MegaSquirt!

[stealth]

I once knew a company that rebuilt these things. Not all were repairable, it basically dpended on how much of a meltdown your had. If it were just leaky caps, not a big deal. if when the board shorted you saw smoke and stuff, then usually that ruins the board itself, which delaminates and is no longer valuable as rebuildable, and they wouldnt give you a core value for it.