Lexus Troubleshooting Questions? Ask a Lexus Expert
Do you have a voltmeter And a reasonable knowledge of how to use it?
Let me look at the wiring diagram. Has any recent work done to the vehicle Leading up to this current problem in the matter how small you think it is?
Do you have access to the ignition switch where the electrical connector goes to it? Just to clarify as soon as you go to the accessory position the fuse blows not the on or start position? Also this problem was never there prior to that you just did?
I just need to make certain that it's the on position if that's the case we will not need to gain access to the electrical connector at the switch. Are you certain?
Okay this rules out anything from the fuse to the ignition switch then. At this point that 15 amp fuse powers up the computer and it powers up the three ignition coils. Look very carefully at the ignition coils and the wiring harness going to the noise/capacitor. It will be a black wire going to it and to the ignition coils. Disconnect those connectors check the harness very closely are any of these wires rubbed or pinched? With all the coils disconnected see if the fuse still blows.
There is also a black wire with a white tracer the goes over to the igniter make sure the harness going to the igniter did not get pinched anywhere. Let me know if you find with these three things.
Did you disconnect all three ignition coils and the noise suppressor/capacitor? Not just one check the harness to all three and the igniter.
The igniter is located on top of the left/drivers strut tower assembly the harness goes down towards the front of the strut tower and by the junction block up over top of the engine regular the harness comes on to the engine area is where the noise capacitor/suppressor is make sure it's disconnected and the harness is okay going to it. If was messed up going to the coils and the copper was green this means it was wet at one time and corrosion could be getting in there. You're more than likely going to find that the harness is screwed up this is what's causing it to short out. That fuse that keeps blowing only feeds ignition coils the igniter and that noise suppressing capacitor.
Simply by disconnecting the coils in the capacitor and igniter rules out the components Which we needed to do but this does not rule out an internal short in the harness. You need to un-tape all of that harness where the green corrosion was and follow those wires in the main harness to make sure none of them are shorting together or to ground. Is the black wire coming off of each ignition coil and the black wire with a white tracer coming off of the igniter.
I would strip that entire harness and replace any wire that has green in it. This way you will know by tracking down the full length of the power feeds that come from that fuse that keeps blowing. You will eventually find the short in there plus you won't have to worry about the wires going open and the thing quitting on you again. If the problem wasn't there prior to messing with the harness and the work that you did it has to be inside that harness somewhere.
Unfortunately I cannot post wiring diagrams here. You could go to www.techinfo.Toyota.com. They do charge a minimal price for a two-day subscription and you could download all of the wiring diagrams for this. They come directly from Lexus.