02 Gt PCM Flash, Fans won’t stop running

Savannahlh said:

Figured it may be a faulty ecm so we got one flashed and now the fans won’t stop running.

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The Mustang uses a "fail safe" cooling control interface to the CCRM. What that means is that in the absence of a signal the default action of the CCRM is to run the fans.

Soooooooooooooooooo. When the cooling fans run all the time, that is a dead give away that the PCM isn't working. Either no power or ground or outright dead.

Savannahlh said:

Still didn’t fix our fuel pressure issue unless this ecm is messed up too? Or I just have another issue completely

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Still didn't fix the fuel pressure problem??????????? So you don't think that it's possible that the fuel pressure problem isn't external to the PCM?

Has the fuel pump been recently changed in this? I can think of several "possible" causes for excessively high fuel pressure in a 1999-2004. For example a ground faulted fuel pump return line would CAUSE the fuel pump to run at 100% duty cycle all of the time. And just in case you are thinking "wouldn't a ground faulted fuel pump power line blow a fuse?". The supply will blow the fuse. The signal return will cause the pump to run flat out.

In all the time I have been helping people on the forums I have never encountered a DTC code the "said" to change the PCM. If you want good help always post the full DTC codes. There are 1,000's and they each have a story to tell.

Regarding the CCRM and cooling fans. IF the CCRM is powered up AND the PCM is not powered this would cause the cooling fans to run all the time. Note, there are multiple reasons WHY this condition could happen. Tests are needed to narrow down. It would be handy to know IF fuse F2.34, F2.2, and F2.8 with the key off and with the key on while this problem is happening.

1999-2004 MY fuse panel schedule:

Just wondering. Are you happy with the "parts changing" method of trouble shooting? Any idea of how much $$ has been spent without a solution?

Let me know when you are ready to perform some detailed tests before the next part is changed.

Your first test is to measure the key off resistance of the trunk mounted Fuel pump Driver module pin #3 (RD/PK) and pin #10 (BN/PK) to a known good ground. Post.

IF the BN/PK (brown/Pink) wire is shorted to ground somewhere in the circuit, this will cause the fuel pump to run at 100% all the time regardless of what the FPDM is commanding. This will cause the fuel pressure to be "off the chart".

Here is some information on an affordable very capable ODB2 scanner with bi-directional support that could prove helpful in providing information to help solve your problem.

ForScan ODB2 scanner w ELM327 USB