Hi All,

Preface - My 4Runner is a 2000 SR5, 3.4 V6 with auto transmission. It has a Hopkins trailer wiring kit installed.



All of the issues outlined below began simultaneously two weekends back, just now getting to troubleshooting. Truck was parked in the garage, hadn't been driven in approximately one week. I started it, pulled it out the garage, then put it in park and shut it off (no issues at this time). After about an hour of sitting outside (no rain or anything) I was going to leave the house and the following issues presented themselves when I restarted the truck and tried to leave:

- Auto transmission will not come out of park without using the override button near the shifter.
(I have checked that the STOP fuse is good, brake lights operating correctly)

- ABS light on, P0500 CEL code, cruise control inoperable, speedometer inoperable.
(these all should be related to the ABS system malfunctioning)

- Power windows inoperable from all switches, including lift gate window.
(The lift gate window works with the key fob button and using key in the tailgate)

- Defroster switch inoperable.
(light does not come on)

- Door ajar light does not come on when any door is opened

It's possible other electrical bits are not working correctly, the list above is what I have found up to now. The following pieces are working normally - power locks, power mirror adjustment, ECT button, exterior lights, interior lights, stereo/speakers, and HVAC. Truck runs and shifts normally when driven. No electrical work has been done in over a year.

About one year ago I tubbed the firewall for 35s, so angle grinder/welding debris was created near the electrical connectors in the kick panels (I wrapped them and moved them away from the immediate area to protect them from debris and heat at the time). And I tipped the truck on its side in Moab last March. I have been driving the truck about once a week since then with no electrical issues, but trying to be thorough.

I was going to start chasing each issue down separately, but it seems pretty suspect that all the issues popped up at once. Looking for advice on diagnosis and order of operations. Hoping @TheDurk , @IBallEngineer , and other electrical gurus can lend their time and knowledge.

Thanks in advance, I have a feeling this is going to get messy.

Do the dome lights come on with the switches on the lights themselves?

Check these fuses:

ECU-B
ECU-IG
DOME
MPX-B

I would first start with cleaning the Batt terminals. Then make sure that all the Grounds are clean and tight. After that you could start chasing wires. Also take a good look at the Batt Cables.

Yes the dome lights come on with the switches.

Good lesson to check fuses first...ECU-B, DOME, and MPX-B all tested good. But the ECU-IG fuse was blown. Replaced ECU-IG fuse and now the transmission comes out of park, defroster button works, and all of the window switches work. Had no idea that fuse played a role in all those.

The door ajar light is still not lighting up.

Thanks for the help so far.

Thanks, checked battery connections and they are clean and tight. No visible issues on the battery cables. Made some progress with a fuse above (since I'm not smart enough to check the easy stuff first apparently).

Do you have rodent issues? It sounds like either an entire connector or wiring harness was cut/shorted.

That was my first thought, I haven't found anything obvious yet and haven't had issues with rodents in the garage before. But still seems possible. The ECU-IG fuse was blown which fixed a few of the issues, but not the door ajar light. ABS seems like it should be separate from the other issues.

Can anyone check if the door ajar light comes in with the key in the ignition in the ON position, without starting the truck? I know it doesn't need the key in to light up normally, but I'm wondering if the bulb is toast.

But do the dome lights come on when the doors are opened? That is, the dash light for door ajar is the only thing left to fix?

And kudos for TESTING fuses. My pet peeve is 'the fuses looked good'

Yes the dome lights are working normally, i.e. when set to "door" they come on when a door is opened but the light in the dash/gauge cluster does not come on. It also does not come on when the key is set to ON, so maybe the bulb went out?

And thanks, I learned the ways of testing fuses and connections a couple years back when you and @IBallEngineer helped me diagnose a fried gauge cluster (which has been replaced for the record).

In that case, it is probably the bulb. Maybe it was burnt for a while but you never noticed until all the rest happened. Otherwise, it would have to be an on-board fault in the ECU-B and thus not worth fixing unless you have one lying around.

Here is all the stuff on the ECU-IG.

If I get motivated at some point I'll look into swapping the bulb (or just ignore it so I don't go down some rabbit hole), but for now all issues are resolved thanks to one fuse change for the ECU-IG. The ABS light turned off once I actually started and ran the truck tonight.

Thanks for the list of things controlled by the ECU-IG, like I said earlier I never knew all of those lived somewhere common and could be affected by one fuse. I suppose with all of the issues popping up so suddenly a fuse would have been an obvious place to check (in hindsight)...I was having nightmares of chasing short circuits when it happened.

I hope you never leave the forum so you can continue helping the electrically-challenged such as myself. Where do I send beer money?


(now this thread can sink into the forum depths before people see that I can't check fuses and I lose all internet credibility)

Glad you got things fixed.

Gawd, I despise electrical gremlins. They drive me up the wall.

Fortunately, my T4R has had very few gremlins - the dash clock and the fuel gauge.

However, once when replacing the dome light bulb, I accidentally made a spark, which blew out the infamous "15 amp fuse". Some idiot engineer put the trip odometers on the same circuit (perhaps they are tied to the ECM?), and I had to write down on paper when my next oil change is due, because my trip odometer B was reset by that spark.

Worst car I ever had for electrical gremlins - a '77 Fiat 124 Spyder. Going down the road at night, every single electric component would go out arbitrarily (lights included), but the engine kept running. I eventually found a connector in the wiring harness, lying under the driver side floorboard carpet. It got kicked by my foot frequently, causing a break in one of the main circuit wires. Incredibly stupid to put a connector there, but Italian car engineers were known for doing really stupid things then (maybe they still are?).
Fix It Again Tony.
Fix It All the Time.

I had a '62 MG Midget. I swear the thing only had, like, three wires and yet it always had electrical issues.

Lucas electrical theory

Bumping this back up, the problem has resurfaced.

The original issue was solved by replacing the ECU-IG fuse.

The current issue is that everytime I turn the key to "On", the ECU-IG fuse pops, so none of the systems that rely on that fuse work.

The issue appeared randomly, no deep water crossings or recent electrical work or things like that. But clearly there is a short somewhere.

I had a trailer wiring kit (Hopkins) installed that I had also tapped into for license plate lights on my swingout, but I removed all that wiring as it seemed like the most likely culprit for an electrical issue. Removing the wiring allowed the truck to operate correctly for about an hour, then the fuse blew while it was running and is back to blowing fuses every time the key is turned to "On".

Does anyone have a wiring diagram for all the circuits that run through the ECU-IG fuse? Troubleshooting help welcome as well.

Thanks.

Here's a link to a 2000 Electrical Wiring Diagram: Dropbox - 2000 4Runner Electrical Wiring Diagram (EWD383U) - Printable - Simplify your life

If I have any time today I'll look at wiring diagrams to see if I can assist in any way.

Edit: If you click on the link, then select 254 Power Source, then scroll down to page 258 it tells you every diagram that contains ECU-IG fuse in the circuit. Hope that helps!

Yeah, there is no such thing. The EWD goes circuit by circuit. PM me an e-mail address and I'll hook you up with the whole set.

This will not be fun. If you can't find the issue by physically looking at suspect areas, such as any modified wiring, then the first thing is to pull the 1G plug on the back of the inside fusebox. Basically, that fuse feeds a bunch of stuff on board the BODY ECU and then a bunch of other stuff elsewhere through that 1G plug. If it still blows with that plug pulled, issue is internal to the BOCY ECU and you know what that means.So I hope it doesn't blow and we can move on to other stuff.