Jump to content

HOWTO: PCM Replacement

Recommended Posts

This guide explains the steps to follow when replacing a failed PCM.

The only PCMs we have seen fail to date are very early BA's which appear to start resetting when very hot or cold which we believe is due to cracks appearing in the PCB. We have also rarely seen injector drivers fail, usually this is due to a failed injector shorting out.

Before assuming a failed PCM do a KAM reset (performed automatically when writing a file to the PCM via PCMTEC) and check your power/ground sources.

If the vehicle has had an engine swap please ensure that you have continuity in your CAN Bus and all grounds are clean.

If you have diagnosed a PCM failure you must replace the PCM with the same part number such as ASU-234 etc. Some part numbers are compatible with others however they will be missing IO. Eg an NA 6 cylinder PCM will work in a turbo vehicle, however the wastegate output will not function. Same goes for an 8 cylinder PCM will sometimes work in a 6 cyl vehicle, but the reverse is not true. To ensure the PCM is compatible with your vehicle we recommend purchasing an identical hardware model.

Step 1:

Read the existing old PCM and save it to disk. Ensure you have ticked "PCM" and within the flash read page. If the PCMwas erased at any stage you can still do this step, but you will need to use recovery mode and manually select the PCM type from the corrosponding dropdowns. Eg for BA select Black Oak, for BF/FG select Spanish Oak. 

This file does not need to be licensed.

Save this read as "Old PCM.tec"

Step 2:

Install the new PCM

Read the new PCM only by ensuring PCM is ticked within the flash read page.

Save this as "new PCM.tec" and do not license the file.

Step 3:

Open the merge wizard via "Create Stock File/Calibration Merge"


Select "Manually Merge VID/Serial"


Step 4

Press "Load File 1" and select "Old PCM.tec"

Press "Load File 2" and select "new PCM.tec"


Step 5:

Next press "Import PCM Serial from File 2"

Press "Save File 1" and save as "Old PCM with new PCM serial.tec"

Step 6:

Now license the file again (will cost 3 credits to license the new file) and write the file to the vehicle.

If you have a custom operating system/multi tune on the PCM please contact support@pcmtec.com and we will refund the credits required to relicense the replacement PCM.

Step 7:

Once you have written the previous calibration to the vehicle the vehicle will be immobilised and will not start. To reset the security system a procedure called a "Parameter Reset" is required.

This last step we cannot warranty and is out of the scope of our support however there are several packages that can do this for you.

FORScan ( www.forscan.org ) is free and can do this for most but NOT ALL Fords. The procedure is located under "service procedures".

If your vehicle is not supported by Forscan you can also use some high end scan tools or Ford IDS/FDRS to perform this step. If you do not have access to either of these you will require a Ford service centre to do it for you. Depending on which state you are in there are several people who can come to you to do this for a fee.

It is not necessary to erase or reprogram keys as part of this process.

Note you can disable PATS to allow the car to be started and drive it to a workshop. This is a temporary measure as by disabling PATS your radio and instrumentation will stop working. In some BAs the radio will continue to work with PATS disabled however it is best to assume that there will be side effects.

A guide to replace the ZF Transmission (or just the TCM) can be found here:


Share this post

Link to post
Share on other sites

You need to pay for the extended licence to use pats reset in forscan, also you can flash a petrol file over the lpg one & keep the same pcm. Fyi .

Share this post

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...