03 to 05 PCM swap

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Soup1213

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At this moment im not looking to do full pcm swap just need rpm to read out for smog. I took it to smog with just the 05 pcm and failed due to it couldnt read rpm.
My original pcm is bad and throws p0443 code
 
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HemiLonestar

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At this moment im bit looking to do full pcm swap just need rpm to read out for smog. I took it to smog with just the 05 pcm and failed due to it couldnt read rpm.
My original pcm is bad and throws p0443 code

You can't just throw in a later year PCM and expect it to work correctly without the corresponding harness changes. You're either all the way in or all the way out on that one.
 

Redtruck-VA

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At this moment im bit looking to do full pcm swap just need rpm to read out for smog. I took it to smog with just the 05 pcm and failed due to it couldnt read rpm.
My original pcm is bad and throws p0443 code

Are you saying your tachometer is dead or are you looking for a rpm output?
 
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chrisp2493

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Rpm signal shouldn’t be effected by any pcm swaps. Sounds like you have more issues then just a computer swap


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Redtruck-VA

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Hemi's don't have a tach output source. I've tried a couple different things to get a tach output. Megasquirt pro uses the crank sensor and will provide a very accurate tach source. Used a tach sq wave generator that didn't work well. Tapped #1 coil and MSD tap from #1 coil. The problem tapping into coils is the signal reflects what the coil trigger is doing. There are certain conditions when the coils are shut down such as decel and rev limiter. I've never used the 03 pcm c4-11 output.
 

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I seen the wire diagram for the 03 has rpm signal for c4 and tcm.
Im not looking to completely wire it up yet just need the rpm to read out with the 2005 pcm to work like normally.
The 05 pcm runs the truck i just need a rpm output for it to pass smog. Rpm readout works fine with old pcm
But when i put the 05 pcm my scanner cant read the rpm nor can the smog test machine read it.


Screenshot_2019-12-09-18-29-38.png


Screenshot_2019-12-09-18-28-23.png
 
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Redtruck-VA

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Where are you looking for engine rpm? OBDII port?
 

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I generally only post on subjects I have had direct experience with and I am surprised you are having the success you are having without committing to a full 05 wiring swap. I had thought a 05 pcm would start a 03 by simply plugging one in but with a dash full of codes. There are the missing O2s and of course the whole TCM that needs wiring. Your OBDII port not working is maybe a blessing as I believe there are codes waiting. On the other hand I don't know why the port isn't working and am afraid you will need to be wired IAW the 05 schematics before being able to properly troubleshoot. Plus you will need to have a trans relearn done before driving.
 

Soup1213

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I generally only post on subjects I have had direct experience with and I am surprised you are having the success you are having without committing to a full 05 wiring swap. I had thought a 05 pcm would start a 03 by simply plugging one in but with a dash full of codes. There are the missing O2s and of course the whole TCM that needs wiring. Your OBDII port not working is maybe a blessing as I believe there are codes waiting. On the other hand I don't know why the port isn't working and am afraid you will need to be wired IAW the 05 schematics before being able to properly troubleshoot. Plus you will need to have a trans relearn done before driving.

It reads from the obd2 port, but only certain thing like im montiors codes but no signal for rpm which is need for emission testing smog. Im surprised it doesnt throw any codes as well
 
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chrisp2493

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It’s gonna throw codes for o2 sensors and EGR for sure without a tune. And it’s probably not gonna run after about 10 minutes when it warms up and doesn’t have a second set of o2 sensors wires it. I had some wiring issues with the sensors on my swap and it would barely run and kept stalling out. You need to either do it correctly right now or order another 03 pcm because it’s not gonna pass the obd2 check without a run for EGR and downstream sensors being turned off.


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Soup1213

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It’s gonna throw codes for o2 sensors and EGR for sure without a tune. And it’s probably not gonna run after about 10 minutes when it warms up and doesn’t have a second set of o2 sensors wires it. I had some wiring issues with the sensors on my swap and it would barely run and kept stalling out. You need to either do it correctly right now or order another 03 pcm because it’s not gonna pass the obd2 check without a run for EGR and downstream sensors being turned off.


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I drove it for few miles and didnt throw no code ran fine just the transmisson didnt shift, so i manually shifted it. I checked the im montiors with obd2 they were all set. Just when i took to get emission tests the machine couldn't see the rpm
 

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Have you C4 (03) plugged in the 05 pcm? I realize it is still unpopulated and is stock 03 wiring. Just curious....
Do you still have the 03 TCM plugged into the 03 harness?
 

Soup1213

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Have you C4 (03) plugged in the 05 pcm? I realize it is still unpopulated and is stock 03 wiring. Just curious....
Do you still have the 03 TCM plugged into the 03 harness?
Yeah i plugged c4 into the 05 pcm. Tcm is connected as should be for 03.
 

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Yeah i plugged c4 into the 05 pcm. Tcm is connected as should be for 03.
I amazed that it isn't throwing codes. Makes me wonder how it would work if you wired the o2s in.
 
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chrisp2493

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The 2005 pcm doesn’t have any pins for “rpm signal” like the 03 C4 connector has. I looked at all the pin outs and the only one that has anything labeled “rpm signal” is C4 on the 2003. So you are doing everything wrong and expecting it to work correctly. If you are wanting to swap to a 2005 pcm for any specific reasons, do the complete swap and it will work right. If you just need to pass smog, buy a new 2003 pcm and continue on. Your P0443 code is just an EVAP canister code which is very typical for old trucks with dry rotted EVAP lines that start to leak. I still don’t understand why your 03 pcm is “broken and won’t work”. Hook stuff up correctly and everything will work out. There’s not much more I can help you with.


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Soup1213

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The 2005 pcm doesn’t have any pins for “rpm signal” like the 03 C4 connector has. I looked at all the pin outs and the only one that has anything labeled “rpm signal” is C4 on the 2003. So you are doing everything wrong and expecting it to work correctly. If you are wanting to swap to a 2005 pcm for any specific reasons, do the complete swap and it will work right. If you just need to pass smog, buy a new 2003 pcm and continue on. Your P0443 code is just an EVAP canister code which is very typical for old trucks with dry rotted EVAP lines that start to leak. I still don’t understand why your 03 pcm is “broken and won’t work”. Hook stuff up correctly and everything will work out. There’s not much more I can help you with.


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Smoked tested all lines and fixed the leaks there was. Put a new purge valve. But the p0443 codes comes on soon as the engine is started. You can reset it and soon as it starts its there.
 
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