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Ask Skyvisions Your Own Question
Skyvisions, ASE Certified Technician
Category: Lexus
Satisfied Customers: 14445
Experience:  Lexus Expert
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Am2 fuse keeps blowing on 02 lexus gs300, The fuse goes out

Customer Question

Am2 fuse keeps blowing on 02 lexus gs300
JA: Tell me a bit more about what's going on so he can help you best.
Customer: The fuse goes out when I turn the switch to acc and it pops and doesn't alow car to try to crank
JA: My old Jeep sounds like a steam radiator sometimes. It must be old age. The Lexus Mechanic will know what your noise means and what to do about it. Are you hoping to fix this yourself?
Customer: Yes
JA: Great! What have you tried so far?
Customer: Replaced fuse a few times tried running a new wire w/r to the ignition new spark plug wire or coil wire has both on this motor
JA: Is there anything else the Lexus Mechanic should be aware of about your Lexus?
Customer: No that's all
JA: Our top Lexus Mechanic is ready to take your case. Just pay the $5 fully refundable deposit and I'll fill the Lexus Mechanic in on everything we've discussed. You can go back and forth with the Lexus Mechanic until you're 100% satisfied. We guarantee it.
Submitted: 1 year ago.
Category: Lexus
Expert:  Skyvisions replied 1 year ago.

Do you have a voltmeter And a reasonable knowledge of how to use it?

Customer: replied 1 year ago.
I do have knowledge but don't have the voltmeter I could buy and test if you could tell me what to test and what to look for
Expert:  Skyvisions replied 1 year ago.

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?

Customer: replied 1 year ago.
Replaced valve cover gasket and spark plugs and wires tried to turn it on and there was a ait leak on manifold and tried 3 times to try to hear leak found leak fixed it and tried to turn it on and when I turned the key it didn't do anything just turn but no crank or anything
Expert:  Skyvisions replied 1 year ago.

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?

Customer: replied 1 year ago.
I believe it's on the on position when I hear it pop
Expert:  Skyvisions replied 1 year ago.

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?

Customer: replied 1 year ago.
I am
Expert:  Skyvisions replied 1 year ago.

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.

Expert:  Skyvisions replied 1 year ago.

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.

Customer: replied 1 year ago.
I tried with the coil disconnected and it still blew on the on position
Expert:  Skyvisions replied 1 year ago.

Did you disconnect all three ignition coils and the noise suppressor/capacitor? Not just one check the harness to all three and the igniter.

Customer: replied 1 year ago.
Where is the igniter
Customer: replied 1 year ago.
I check the harness on the coils yesterday and all 3 we exposed and touching together at a point in the harness so I separated and taped them so they would touch but the copper was green not the normal copper color
Expert:  Skyvisions replied 1 year ago.

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.

Customer: replied 1 year ago.
Okay I found and unplug all 3 coils the igniter and noise capacitor and it still blew
Expert:  Skyvisions replied 1 year ago.

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.

Customer: replied 1 year ago.
Would I have to cut and replace the corrosive wires
Expert:  Skyvisions replied 1 year ago.

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.

Customer: replied 1 year ago.
No it wasn't there before ran perfect only has 110k do you know where I could get color diagram for coil packs don't want to mix then up
Expert:  Skyvisions replied 1 year ago.

Unfortunately I cannot post wiring diagrams here. You could go to 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.