02 Gt Won't Start After Motor And Transmission Swap

Matt Boyd

New Member
Apr 26, 2017
5
0
1
48
Hey all,

I did a motor and transmission swap in a 2002 GT automatic car. I installed a 2004 Cobra motor and T-56 transmission. I used the GT wiring and had a chip programmed and added it to the factory computer. I got everything wired up and the car wouldn't even turn over. I ran direct power to the starter and it turned over, but the car was not getting fire or fuel. After messing with it for a few minutes, the fan started kicking on when the key was turned on and the odometer was showing all dashes instead of mileage. Come to find out the chip and computer are burnt up.

I have no idea how I could have burnt the computer and chip up by trying to start the car. I would have thought if there was short somewhere, it would have blown a fuse first. I got another computer and I am getting another chip. Should the car turn over without the computer? I would think that it would turn over, but would understand it not starting.

I also believe that it is not turning over due to switching the car from an auto to the 6 speed and the computer searching for the signal that the car is in Park or Neutral. I need some help on what to do here... I should be able to close this circuit somewhere so that would not be an issue. Also, the PATS is disabled via the chip.

ANY HELP WILL BE GREATLY APPRECIATED!

Thanks,
Matt B
 
  • Sponsors(?)


wmburns

SN Certified Technician
Aug 14, 2009
5,669
470
164
Houston Texas
What an awesome project! Let's see if we can get you some help.
I have no idea how I could have burnt the computer and chip up by trying to start the car. I would have thought if there was short somewhere, it would have blown a fuse first.
Usually you are correct. IF there's a short to ground in a POWER circuit it will blow a fuse. Likely what you have isn't a power circuit short to ground. But perhaps power being applied to PCM pins that are not designed to accept power. Another possibility is a sensor that is supposed to supply a "load" on a PCM circuit is shorted out. This causes excessive current to flow through the PCM in a circuit not designed for it.

I strongly encourage you NOT to install the new PCM until you have found the REASON why the old one failed. A PCM is an $$ part to ruin.

Have you "mixed" any parts from different model years or different cars? I frequently find that many people are not aware that Ford does make small changes across the model years. There are differences in the wiring harness between a 2002 and 2004. There are differences between a manual and automatic car. There are differences between a GT, V6, and Cobra. When combining parts from different model years having a full set of wiring diagrams can be a huge help.

Should the car turn over without the computer? I would think that it would turn over, but would understand it not starting.

I also believe that it is not turning over due to switching the car from an auto to the 6 speed and the computer searching for the signal that the car is in Park or Neutral. I need some help on what to do here...
Yes your car should be able to crank without a PCM. The starter pilot duty circuit does not go through the PCM.

And yes you are correct there is a jumper installed in connector C263 between pins 1 and 2 to bypass the Clutch Safety switch (CSS) in an automatic car. Further there's a difference in the wiring harness between an automatic and manual car. This is where the details of what parts were mixed and matched are important. And don't think that the connectors won't or shouldn't interchange. Because Ford didn't build the car with the idea in mind of people doing what it is you are doing.

For an automatic to manual swap with the automatic wiring harness still in the car, it would be necessary to jump pins 10 (RD/LB) and 12 (WH/PK) in the transmission DTR connector C167.

Here's another case where having a full set of Ford wiring diagram can be a huge help.

If interested in getting a set for yourself I maybe able to help. PM if interested.

Here's another recent thread on how to chase down a short to ground in a power circuit.
https://www.stangnet.com/mustang-forums/threads/keep-blowing-fuse-6-under-dash-starter-relay-fuse-when-turning-let-to-start-pushing-clutch-in-5sp.898130/
 
Last edited:
  • Like
Reactions: HawkX66

Matt Boyd

New Member
Apr 26, 2017
5
0
1
48
I really appreciate the response! The changes to the car are the terminator motor out of an 04 Cobra and the T56 transmission. We used the GT harness, flippped polarity on the COP wires ( we were told we had to do that), and extended the COP wires. This is a father/ son project with help from a friend. My son worked and saved his money to do the swap. Now we are over budget and way over the time we thought it would take. We may be in over our heads. Never expected all of this with the wiring.
I got a new computer and I am waiting on the chip to bet programmed. The transmission harness is really difficult to get to. Is there anywhere under the dash or in the engine compartment that we can jump those pins?

Thanks!
 

Matt Boyd

New Member
Apr 26, 2017
5
0
1
48
I found a couple of wires that I had hit with a drill when running wires to the fuel pumps. ( we put in a return style system). We think that was the problem with the short and I have fixed those wires.