Going to be troubleshooting my ECM. Thought I'd start with a post. Did a quick search and only found a few threads with mention. So figure this would be a good place to store a how to troubleshoot and replace.
History is that I had a fire over the passenger side exhaust manifold. This melted a good chunk of the primary wiring harness from the fuse box that is attached to the firewall and runs end to end to connect to the ECM as well as into the cabin. Also, a lot of heat to the main engine wiring harness. I haven't done a full dissection yet, but it actually doesn't look as bad as far as any actually melted wiring.
I've completely replaced the main engine harness with a new (used) harness, and I've repaired the harness that goes along the firewall. I put a battery back on the truck and everything in the cabin, doors, windows and all that type of stuff is working fine (although I don't believe any of that stopped working originally). I still have lights in the dash for VGRS and VSC and AFS. With my OBD2 dongle I am able to see codes and read ECUs that are on the secondary network (on my 2010 LX Network "A" - pretty sure it's different on other models). The other big one is no gears show up in the dashboard when ignition turned on. Switching gears does trigger the "park" and "reverse" switches as I still get the "you are not in park warning" and my rear camera comes on when in reverse.
So the big thing right now is when I connected the OBD tool, it will not find the "generic OBD2" when it scans. It will find and connect to devices on Network A and Network E.
My first steps of course will be to verify wiring and power to the ECM. I've included the page from the FSM to this post for anyone in the future looking for such things. Maybe I'll get lucky and it is a fuse or relay ( I quickly checked fuses, but was out of daylight and didn't have the FSM up and running yet). It appears the ECM part is still available from Lexus and is "reasonably" inexpensive. I have Techstream (for programming the VIN if necessary) and i've seen videos now that suggest you can sync the immobilizer with a paper clip in the right location of the OBD2 connector. I suspect there is a good chance though that you need the version of Techstream that only locksmiths can have to deal with the immobilizer.
The immobilizer is one part that was definitely broken and is now working again, as when the key is in the truck and the brake is depressed the Start button indicator turns from amber to green. That definitely had stopped working before the wiring repair.
Either way, posting here in case anyone has any in depth knowledge on how the different systems talk to each other. I know there is a gateway ECU and then most of the systems talk to each other over the CANBUS. Not being able to see anything when scanning generic OBD2 though i assume means that the ECM is probably fried (or hopefully not connected to power). Also, according to the parts sites, my ECM has been superseded by a new part (also the part for the year before mine). Does everyone think it's pretty reasonable that the new part is still good for my vehicle if they have declared that it's been superseded?
History is that I had a fire over the passenger side exhaust manifold. This melted a good chunk of the primary wiring harness from the fuse box that is attached to the firewall and runs end to end to connect to the ECM as well as into the cabin. Also, a lot of heat to the main engine wiring harness. I haven't done a full dissection yet, but it actually doesn't look as bad as far as any actually melted wiring.
I've completely replaced the main engine harness with a new (used) harness, and I've repaired the harness that goes along the firewall. I put a battery back on the truck and everything in the cabin, doors, windows and all that type of stuff is working fine (although I don't believe any of that stopped working originally). I still have lights in the dash for VGRS and VSC and AFS. With my OBD2 dongle I am able to see codes and read ECUs that are on the secondary network (on my 2010 LX Network "A" - pretty sure it's different on other models). The other big one is no gears show up in the dashboard when ignition turned on. Switching gears does trigger the "park" and "reverse" switches as I still get the "you are not in park warning" and my rear camera comes on when in reverse.
So the big thing right now is when I connected the OBD tool, it will not find the "generic OBD2" when it scans. It will find and connect to devices on Network A and Network E.
My first steps of course will be to verify wiring and power to the ECM. I've included the page from the FSM to this post for anyone in the future looking for such things. Maybe I'll get lucky and it is a fuse or relay ( I quickly checked fuses, but was out of daylight and didn't have the FSM up and running yet). It appears the ECM part is still available from Lexus and is "reasonably" inexpensive. I have Techstream (for programming the VIN if necessary) and i've seen videos now that suggest you can sync the immobilizer with a paper clip in the right location of the OBD2 connector. I suspect there is a good chance though that you need the version of Techstream that only locksmiths can have to deal with the immobilizer.
The immobilizer is one part that was definitely broken and is now working again, as when the key is in the truck and the brake is depressed the Start button indicator turns from amber to green. That definitely had stopped working before the wiring repair.
Either way, posting here in case anyone has any in depth knowledge on how the different systems talk to each other. I know there is a gateway ECU and then most of the systems talk to each other over the CANBUS. Not being able to see anything when scanning generic OBD2 though i assume means that the ECM is probably fried (or hopefully not connected to power). Also, according to the parts sites, my ECM has been superseded by a new part (also the part for the year before mine). Does everyone think it's pretty reasonable that the new part is still good for my vehicle if they have declared that it's been superseded?
