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Old 02-09-2013, 09:29 AM   #9
Capt. Obvious!
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Join Date: Jan 2013
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What I Drive: 04 ZX3 S/C, 87 VW cabby, 98 Opel

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Question ECU W/ custom tune replacement questions

Why I think I need to replace it
After much diagnosis and trouble shooting, I've come to believe that my ECU is shot. It appears I no longer am getting signal to my voltage regulator telling my alternator to charge. I've checked continuity and voltage drop on every wire related to the charging system. I've replaced the alternator twice and the battery once. Checked every ground under the hood and cleaned and tightened every connection on them. I've done every bit of diagnosis I can do that I know of without an oscilloscope or access to the Ford PID's. Nothing has changed the results. The only thing that has worked to allow the alternator to charge the battery is to disconnect the wire harness from the voltage regulator. This allows the voltage to go to 13.8v (with the engine running) opposed to 11.9v with the regulator plugged in.

What I think I want to try
I want to try replacing the ECU if I can find one to see if that fixes it, But I need to know what I will need to do to flash the ECU. I have the SCT flasher unit with the current good tune on it (yes I even tried reflashing it). Will I be able to use this to flash the new ECU or will I have to buy an additional program or something to make it work? I'm afraid it may not mate to the new ECU since it's already been use on the one that's in the car. I'm not sure if the SCT units work like that or not.

The ECU connector has "LUY4" written on it. Is this the number of the ECU I would need to buy?

Other options
My last resort is to rig up an older style system somehow. Either using this alternator with the regulator disconnected and using an external regulator, or even an older style alternator with external regulator. this will however turn on the indicator light on the dash, which I would like to avoid.
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