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Chris (aka-Moose)
Chris (aka-Moose), Auto Technician
Category: Toyota
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Experience:  16 years of experience
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I have an efi fuse that keeps blowing on a 2002 corolla le

Customer Question

I have an efi fuse that keeps blowing on a 2002 corolla le 1.8l 4 cyl A/T.
Submitted: 7 months ago.
Category: Toyota
Expert:  Jared D replied 7 months ago.

The most common cause that I've seen of the EFI fuse blowing on a corolla is the wiring to the rear O2 sensor. Have you inspected the wiring to that sensor yet?

Also, the fuse blows the second you turn the key to run right?

Have you attempted to unplug the PCM and then turn the key to see if it still blows?

Expert:  Jared D replied 7 months ago.

It makes sense to start with the most common, but ultimately you will want to disconnect the evaporative vacuum switching valve, the canister closed vacuum switching valve, the idle speed control valve, the mass airflow meter, both oxygen sensors, the idle speed control valve and the circuit opening relay located on the back of the passenger's compartment fuse box. Then with the key on, plug each sensor back in until the fuse blows. Once the fuse blows you know that sensor is the problem.

Customer: replied 7 months ago.
i got to the rear o2 sensor. what should i have to verify that something is bad? we disconnected the o2 sensor and are still trying to get it unstuck from the exhaust. the circuit opening relay as i know it is on the drivers side and that as we have been trying to solve this has now gone bad. when i first checked it it was fine. if i have the ecm disconnected, the battery disconnected, the main fuse out, should i have continuity on the b+ and the ground on the rear o2 sensor wire harness? makes no sense to me.
Customer: replied 7 months ago.
i have everything you listed already disconnected. but its hard at this point to want to put power back through the system. the camshaft position sensor registered 0 ohms when i pulled it. That would mean its shorted right? and can you tell me what the pin out is for the park neutral switch is?
Expert:  Jared D replied 7 months ago.

You should not have b+ on the ground side of the o2 sensor.

Yes, 0 ohms on the cam sensor means an internal short in the sensor.

The part neutral switch shouldn't run through the EFI fuse. It runs through the IGN fuse. Let me see if I can find a pin diagram.

Customer: replied 7 months ago.
i have at least continuity between the pins. which yeah doesnt make sense. especially with the ecm and stuff gone. the park neutral could have shorted the ecm or something. and it decided during diagnostics to not shift. so we are checking. when i look at the schematics i can trace a short from p/n to efi.
Expert:  Jared D replied 7 months ago.

Here is the junction connector schematic for the neutral safety switch.

Expert:  Jared D replied 7 months ago.

I need to call it a night. Do you want me to opt out and see if anyone else is still online or do you want to pick up again tomorrow?

Customer: replied 7 months ago.
trace a short" as in, i can draw a line with my finger on paper :)
what pins do i check for continuity on on the switch?
Customer: replied 7 months ago.
i could really use an answer tonight if possible. otherwise as Early as possible tomorrow.
Expert:  Jared D replied 7 months ago.

You should see continuity between pin 9 and 6 when in neutral or park. The problem is, I can't find a diagram that labels the pins.

Customer: replied 7 months ago.
the one in the haynes is close. but its not the same. it has the pins on the top not matching what i see on the switch. the larger pins are switched compared to whats shown in the book and i get continuity the same. but i do not get the rest... so i need someone or something that is for sure for a 2002 corolla le, how to verify
Customer: replied 7 months ago.
the harness has numbers but they don't match anything that can be because some of pins slots that are numbered don't have wires lol
Expert:  Jared D replied 7 months ago.

Here is the chart that toyota lists for the 2002 corolla. It says except taiwan made.

Basically follow the lines on the chart. I.E. in park 9 and 6 connect, Reverse 2 and 3, neutral 9 and 6, drive empty(?) and 3...

I'll opt out. That will open it up to anyone else still online. If I don't see anyone pick it up I'll check back in with you in the morning.

Customer: replied 7 months ago.
Expert:  Chris (aka-Moose) replied 7 months ago.

Welcome, I'm Chris (aka Moose). Experts aren't employees / agents of Just Answer. We are independent service providers using the Site to sell their Expert knowledge to Customers. I strive to provide EXCELLENT 5 STAR service, let me know what's needed from me so your pleased.


  1. The previous tech has opted out, would you like me to try and help?
Expert:  Chris (aka-Moose) replied 7 months ago.

Hello again Chris here,

1) When customers come to Just Answer the website and the experts want them to have a great 5 star experience.

2) We also want them to be so pleased that they come back for future needs.

3) I have the feeling you were not pleased with my help and or need me to help more. If so please do reply.

4) I have an option to upload diagrams, repair guides, find a repair facility, or call you if that would help.

Thanks Chris

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