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The short has been found! Believe it or not, when I bypassed SBF 5 power was sent through four relays, fuel pump, main, A/F O2, and electronic throttle control, along with two terminals of the ECM, out terminal 4 of the main relay and to the power supply for the pressure control solenoid and the drain valve of the evap canister.
Although I did not find the actual short or wires burned together, I did find evidence of where the wire was heated and discolored as it came through connector R57. It had also been hot enough to melt some of the sound deadening material before the harness went into a grommet and out the floor. The reason I couldn’t see the actual short is because that section of the harness is routed above the gas tank, then goes to the evap canister. I cut the wire at R57 and made sure it wouldn’t contact anything and disconnected the pressure control solenoid and drain valve.
That is both my concern and conclusion at the moment. I still have some testing to do in order to confirm or rule it out.
Thanks for your reply.
Yes, I replaced the fuse and it blew again. With the correct fuse and new main relay installed is when the CEL flashed and the fan cycled.
I haven’t tried to read codes since SBF 5 is the battery or constant power supply to the ECM. As stated, the fuse blows almost instantly so I don’t want to damage the ECM. For test purposes I am using a 30 amp circuit breaker in the place of the fuse.
I have unplugged everything in the direct power supply from SBF 5. I have also unplugged the harness to the fuel pump after testing it for functionality, and unplugged all sensors and components powered by the affected side of the main relay.
I agree with you that there is a wiring issue somewhere, just a matter of finding it. I will check out the CAN bus communication and 5V ref that the rest of the sensors are on.
