I've been having some strange engine electrical problems lately, which seem to get worse when it's humid. So I've been going through all of the engine electrical, replacing sensors and checking wiring.
Now things have just gotten really weird.
The starter will crank, the engine turns over, but doesn't fire. However, if I plug a cable into the OBDII plug, the engine fires up and runs perfectly. There's nothing connected to the cable - it ends in a serial plug (meant to plug into a USB OBDII reader).
I would just leave that plugged in and call it good, but when it's plugged in the socket and the wiring under the dash gets really hot. I'd prefer not to have to use the fire extinguisher...
I checked that pins 4 and 5 are grounding properly and 16 is getting correct voltage when the key is on.
Ideally I'd like to figure out where the connections for the OBD plug terminate so that I can check all of that wiring, but the wires disappear into a bundle of wires I've not been able to trace through yet.
Does anyone know where the OBD wires terminate and/or have any ideas as to what might be causing this?