First check for a wiring harness for the oxygen sensors that fell down onto hot exhaust parts.
A simple trick to finding a short is to replace the blown fuse with a pair of spade terminals, then use small jumper wires to connect them to a twelve volt light bulb. A brake light bulb works well. When the circuit is live and the short is present, the bulb will be full brightness and hot so be sure it is not laying on the carpet or against a plastic door panel. Now you can unplug electrical connectors and move things around to see what makes the short go away. When it does, the bulb will get dim or go out.
There is a clinker with this circuit. The automatic shutdown, (ASD) relay only turns on for one second when you turn on the ignition switch. That is enough time for the fuse to blow, but not enough time to diagnose anything with the light bulb in place of that fuse. The ASD relay turns on again during engine rotation, (cranking or running), and it is not practical to crank the engine for very long. The perfect solution instead is to install a new fuse, then use the test bulb in place of the relay. The ignition switch does not even have to be on. This will power up the circuit without having to crank the engine, and the bulb will still be in the circuit to limit current to a safe value. Put the test light's terminals in the relay socket's terminals 30 and 87. The bulb should be bright. Now move wiring harnesses around and unplug things to see what makes the light go out or dim.
Items fed by the ASD relay include the ignition coil, injectors, alternator field, oxygen sensor heaters, and some emissions system valves. On other models the fuel pump or pump relay is also on that circuit, but as I recall, your fuel pump relay is on its own circuit.
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Tuesday, February 13th, 2018 AT 5:38 PM
