I have decided that I want to get into this business. I am currently a mechanic, but I have done a little board repair on ECUs for Lexus with bad caps. Now I want to take my knowledge much further than just replacing caps, I would like to be able to test and repair these devices and start moving more toward that than turning wrenches all day. I have the Car Hacker's Handbook, many books on assembly programming and C, The Art of Electronics, etc., and many other related topics waiting for me to read finish getting through them, but I thought I'd start with an old Lexus computer that I have the pin out for. Any advice would be appreciated! I have numerous electronics tools, though I could use a better scope and scanner.
I picked up a 1997 Ram with a 5.9 and 46RE. It looks like the PCM might be dead. I found Keenans Youtube video about opening a JTEC PCM and realized I was on the right track looking for a voltage protection diode. However, my PCM doesn't exibit such a failure. When I turn the key on I'm getting voltage at the two 5v supplies (4.5 on one and 3.5 on the other) I don't get any response from a scan tool or the check engine light when doing a key self test. No lamps from the PCM appear to work, and the ASD and FUEL pump relays aren't getting their ground. I removed the PCM and supplied bench power, wired up a DLC between the PCM SCI TX/RX and a ELM327 scanner and am unable to get a connection. I then wired a small bulb up to the MIL driver pin and get nothing. I checked this pcb over pretty closely and can't see any signs of poor solder joints or broken traces. Where should I go next? I feel like the simple, few skills needed, easy to diagnose failures are accounted for.