Can a PCM be bench tested?
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5th Wheeling
Joined: Nov 2009
Posts: 32
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From: Southeastern Vermont
Can a PCM be bench tested?
Just wondering now that I have it on the table, before I buy a new one for no reason other than the practice of r&r'ing one...Can mine be brought somewhere to determine if it's n/g?
Senior User
Joined: Jul 2004
Posts: 247
Likes: 3
From: Illinois
no
nope
my local dealership here told me that they have "known good" PCM's to swap into too see if that's the problem
they also told me that PCM failure is very rare and that's probablyy not the problem
turns out, it wasn't my problem
my local dealership here told me that they have "known good" PCM's to swap into too see if that's the problem
they also told me that PCM failure is very rare and that's probablyy not the problem
turns out, it wasn't my problem
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5th Wheeling
Joined: Nov 2009
Posts: 32
Likes: 0
From: Southeastern Vermont
I guess I'll find out. I have a good, used one coming in 2-3 days. All avenues lead to the PCM in my case, so that's the gamble I'll take. For $125.00 with a 90 day warranty, it's worth the shot at this point.
Elder User
Joined: Jan 2008
Posts: 605
Likes: 1
If you let the smoke out of your PCM you MUST find the fault or you'll end up letting the smoke out of the replacement too. Do you have an input or output to the PCM that is feeding excessive current to the PCM? More than 1.2 amps for 6mSec is excessive. You need to check the resistance of all your inputs and outputs to be sure the resistance is within spec. When resistance goes down current goes up and the smoke comes out.
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5th Wheeling
Joined: Nov 2009
Posts: 32
Likes: 0
From: Southeastern Vermont
I created a dead short in my system the other day that blew the fuel pump fuse, and a couple others. Since replacing all fuses, I did a thorough check of all systems. The issue is I have no spark, no injector pulse, and the OBD scanners (two different ones to be sure,) all read "error" and wouldn't communicate with the PCM. I also lost digital readout in the dash; tripmeter displays "---------" which isn't a health sign.
After all the testing procedures I went through, I just came to the conclusion I fried the PCM, and for a mear $125.00 I'll find out if I did or not come this Monday when it arrives via UPS.
I searched high & low for any more fuses and fuseable links to see if I missed a blown one, but I do not have any others than the under -the -hood power dist. box, and the fuses under the dash. One fuseable link on the battery cable ON the battery itself, checked out OK.
It's the final resort, and the only thing I could think of that would do this.
After all the testing procedures I went through, I just came to the conclusion I fried the PCM, and for a mear $125.00 I'll find out if I did or not come this Monday when it arrives via UPS.
I searched high & low for any more fuses and fuseable links to see if I missed a blown one, but I do not have any others than the under -the -hood power dist. box, and the fuses under the dash. One fuseable link on the battery cable ON the battery itself, checked out OK.
It's the final resort, and the only thing I could think of that would do this.
New User
Joined: Dec 2009
Posts: 3
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Tommy
I'm having a similar problem as u, I went to start my truck today and it wouldnt start looked down at the Odometer and Saw "-----------" and it would never start when it was all dashes, but after turning the key on and off a couple times I got the Odometer Mileage Numbers to come back on and Then it would fire right up. Im starting to think my PCM is also going bad.
Very Curious to know it that Computer had Fixed your problem.
Thanks Cybulski
I'm having a similar problem as u, I went to start my truck today and it wouldnt start looked down at the Odometer and Saw "-----------" and it would never start when it was all dashes, but after turning the key on and off a couple times I got the Odometer Mileage Numbers to come back on and Then it would fire right up. Im starting to think my PCM is also going bad.
Very Curious to know it that Computer had Fixed your problem.
Thanks Cybulski
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New User
Joined: Nov 2009
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PCM swap...n/g
Cybulski, I struck out last night with the used pcm swap out. I still have the same exact symptoms I had a week ago before I put it in. I'm missing something somewhere else. I even got desperate (or mad,) and spent the $15.00 on JustAsk.com to get nowhere with asking for advice on that site from various techs that are supposedly standing by to help out. He just told me to check everything I already had 2-3 times.
Somewhere there has to be a fuse link or a feed/ground that got hurt, that's keeping the pcm from communicating with an obd II scanner. I have a friend that's a class 1 tech working on a schematic for me this morning to try and narrow down the search for another cause, and if I don't get it today, I give up. I'll have it dragged to a guy I know who is a Ford specialist and have him deal with it. This thing will end up being the grinch that stole Christmas at that point.
Somewhere there has to be a fuse link or a feed/ground that got hurt, that's keeping the pcm from communicating with an obd II scanner. I have a friend that's a class 1 tech working on a schematic for me this morning to try and narrow down the search for another cause, and if I don't get it today, I give up. I'll have it dragged to a guy I know who is a Ford specialist and have him deal with it. This thing will end up being the grinch that stole Christmas at that point.
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Freshman User
Joined: Mar 2004
Posts: 41
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From: Alberta
Sorry but you just can't swap out a PCM. The PCM, Instrument Cluster, PATS transceiver, and programmed keys are all married together when the truck leaves the factory. If any of these items are replaced, the Theft Light will flash rapidly shutting down the fuel system.
Rob/HBT
Rob/HBT
Lead Driver
Joined: Sep 2006
Posts: 7,907
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I am sorry to say this without causing you ill feeling but you have NO idea what you are doing with these systems being computer controlled and all the subsystems that feed data to the PCM as well.
Example that you cannot change PCM and expect the motor to start even if there were NO troubles of any sort, before hand.
Nothing we could tell you would solve your issue because there may be multiple issues at this point, we could not account for, with any amount of guessing.
Good luck and be more carefull with what you do in the future.
Example that you cannot change PCM and expect the motor to start even if there were NO troubles of any sort, before hand.
Nothing we could tell you would solve your issue because there may be multiple issues at this point, we could not account for, with any amount of guessing.
Good luck and be more carefull with what you do in the future.
Elder User
Joined: Jan 2008
Posts: 605
Likes: 1
When you connect(or try to connect) your scan tool to the DLC it becomes another module on the network. If it doesn't connect there is a reason why. Is it your scan tool at fault or is it the network. Will your scan tool connect to another vehicle? Is your network shorted to power or ground? Can you see activity on the network? Have you made these checks using your DSO and DVOM? It has already been mentioned that you don't just plug a replacement ECM in with doing thorough checks first unless you want to throw away money. You must fix the problem that took out the first ECM before you install the replacement. Do you have too much current on the network? Have you checked all the inputs and outputs to the ECM? Do you have Alldata, Mitchell or Identifix? If you're an iATN member you can ask for help there. You already know Just Ask is a wasted of time.
New User
Joined: Nov 2009
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When you connect(or try to connect) your scan tool to the DLC it becomes another module on the network. If it doesn't connect there is a reason why. Is it your scan tool at fault or is it the network. Will your scan tool connect to another vehicle? Is your network shorted to power or ground? Can you see activity on the network? Have you made these checks using your DSO and DVOM? It has already been mentioned that you don't just plug a replacement ECM in with doing thorough checks first unless you want to throw away money. You must fix the problem that took out the first ECM before you install the replacement. Do you have too much current on the network? Have you checked all the inputs and outputs to the ECM? Do you have Alldata, Mitchell or Identifix? If you're an iATN member you can ask for help there. You already know Just Ask is a wasted of time.
I just hauled it to a man who has been a Ford tech at a now defuncted dealership for over 20+ years with his own garage now. If he can't figure it out, no one can. I asked multiple questions in multiple arenas, and got multiple answers. JustAnswer.com has to be the worst mistake I made. Just blessed somebody with $15.00 that's all. 3 different veteran Ford service techs, all bewildered on this one. Without having the vehicle and physically testing everything, they can't diag something like this. I gave it the all-American try as hard as I could for one simple reason...I'm not a rich man...can't fault me for trying...
Elder User
Joined: Jan 2008
Posts: 605
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I don't believe there is a specific or universal test fixture to put a ECM through its' paces. If there is I've never heard of it. That's why you have to use other methods to first condemn the ECM and then to test the replacement. Before you install the replacement ECM you must find the cause of the fault and repair that before you install another ECM or you're just throwing money away buying replacement ECMs
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