How to open / repair 2004 Mazda 3 ECM/ECU?

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Oct 22, 2023 | 07:13 AM

TexasJohn

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Joined: Oct 2023

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From: Austin, Texas

How to open / repair 2004 Mazda 3 ECM/ECU?

My problems started with a P0715 Transmission Input Speed Sensor error, so I replaced the sensor but no joy. Tested wiring up to ECM - (resistance) and it is OK; also checked signals with oscilloscope while car is running on pins 4 & 5 (from firewall) of ECM connector closest to firewall on passenger side of connector - signal looks good. So this leaves ECM which I removed it and carefully removed the top by scratching out all the sealer and slightly unbending the side tabs. It has 2 of 220 mfd 50V 125 degree C Capacitors which I would like to replace as I am suspicious of old electrolytic capacitors. Got 2 from DIgikey.com (also like/trust Mouser and Newark for electrical parts). To replace them, I need access to the back of the circuit board.
But I don't know how to remove the bottom plate which is about 1/4 inch (6mm) thick (perhaps a heat sink?). I removed the 4 screws in the corners which were under a layer of the sealant/glue and the 2 screws from the inside that attach the circuit board to the bottom thick plate. Plate is glued to the plastic housing very tightly by the same sealant as the top cover. Can't seem to get a knife in between housing and plate to separate them.
Suggestions welcome as obviously I do not want to damage anything.
Thank you.