No PWM signal from ECU to 1+4 Coil - Miata Turbo Forum - Boost cars, acquire cats.

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Old 09-29-2013, 11:55 AM   #1
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Join Date: Sep 2013
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Default No PWM signal from ECU to 1+4 Coil

After a lengthy diagnososis I found the CAS and both Coil packs to be working well. Back probed pin 4N on the PCM (The Brwn/yel wire that goes to the 1+4 coil) and instead of seeing the normal square wave I got IGN+. That means to me the Coil driver is not grounding the circuit.

So, I need a new ECU. Maybe... Does anyone know what component on the board is the driver? I see two large Transistors on a heat sink and I have two coils..... I also see 4 transistors in a row that go to the area of the injectors. My concern about the two big guys is that the circuit for turning the coils off is low current, so why would it need a heat sink.

I'm buying a new (to-me) ECU anyway. The numbers on mine are:
BP3A 18 881R 0B

Are all BP3A compatible? I cant find any information for any of these things.

(Yes, I should go MS, but I'm having a hard time convincing the wife that my ECU is more important than a down payment on a house)
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bp3a, ecu

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