4g63 engine fuse blew, and keeps blowing

[97gst_spyder]

I have already searched this while sitting on the side of the road (where I still am). I was driving home like normal, the I gave it half throttle and a pop and jerk later stranded in the left turn lane. I found that the engine fuse 20a, was blown to shit. I swapped another on there thinking that it was just old. Nogo, as soon as it touched the box, gone. I ended up unplugging everything in a list I saw ECU (pins 12 & 25), injector resistors (and from these to injectors), front O2, rear O2, CPS (crankshaft position sensor), CAS (camshaft angle sensor), volume air flow sensor (aka MAF), idle air control motor (aka IAC), turbo waste gate solenoid valve, fuel pressure solenoid valve (this is not the FPR), evap emission purge solenoid valve, egr solenoid valve, and on the 98 & 99: evap emission vent solenoid.

Nothing... It still blew instantly.

Any ideas?

 

[LambdaJoker]

you might have a short in one of the wires. inspect all wiring and make sure all connectors and plugs are clean. if your fuse keeps blowing, im pretty sure its a shorted wire.

 

[dsmdeliveryboy]

Go through your harness and check for frays etc

 

[nfgrocks1028]

I agree with the shorts from a wire. Same thing happened to me when I was changing my A/F gauge. One of the wires was still hooked up and shifted. Blew my engine fuse. But definitely sounds like a short.

 

[97gst_spyder]

The harness is bone stock. Nothing added. Nothing changed.

I finally just got home. Got some more fuses, the wire from the battery to fuse to relay is good sadly, its so easy to fix. So I guess ill start at the ecu tomorrow.

 

[luv2rallye]

Read 2nd paragraph here: http://www.dsmtuners.com/forums/art...-partial-short-battery-drain.html#post1496998

 

[pindlepiper]

I am having this exact same problem on my 97 gst. The car ran like a champ, switched from AEM to Link V3 and noticed the previous owner butchered the wiring harness. I redid all the wiring put the v3 ecu in and the car ran rough. We got a base tune on it and took it for a WOT drive and i keep blowing the Engine Fuse 20a under boost. It will start and idle fine all day, but when i drive it it pops the fuse. I have looked my wiring over numerous times and cannot find the solution. One thing i thought was weird though, the previous owner had the front and rear o2 sensor wires (white) connected to each other instead of pins i believe is 75 and 76. I hooked the front o2 sensor wire back up and ran my wideband to the rear o2 pin on the ecu. Also i read on one thread here that pin 92 (sensor ground) and chassis ground should not have any continuity between them. I am getting continuity between them so maybe thats also an issue. I put the AEM back in and i still have the same problem. Its getting really frustrating.

 

[97gst_spyder]

Funny you brought this back up!

I had mine break down 4 times on the way to work today. Oil filter came off first, then the alt felt suicide, after that the engine f use blew again, then I wiggled the harness from the fuse box to ecu, 'fixed' that the 2nd time, last but not least ic coupler blew clean off both pipes.... Sweet 20mile trip to work, after all that I just drove home and called it a day...


As for you pindlepiper, I'd just get a new harness. There under a $100 shipped anymore. Then you can have a running car, then create a custom harness for your car out of the old one. Thats what I'm doing somewhat.

 

[luv2rallye]

Also i read on one thread here that pin 92 (sensor ground) and chassis ground should not have any continuity between them. I am getting continuity between them so maybe thats also an issue. I put the AEM back in and i still have the same problem. Its getting really frustrating.

On a 2g (but not 1g) ECU pin 92 (note: this pin is incorrectly labeled Ignition switch on some 2g ECU pinout diagrams) goes to the signal grounds of the following engine sensors: manifold diff pressure, engine coolant temp, front O2, rear O2, TPS, volume air flow (MAF), and on the 98 & 99 fuel tank diff pressure. Pin 92 is grounded inside the ECU but all these sensors signal grounds must NOT be grounded anywhere but through pin 92 to avoid electrical noise and ground loops from affecting the sensors differential signals and to guarantee that the sensor's ground is at the exact same voltage potential as the ECU ground (which it might not be with large current flowing through any other ground). Some people and even some mechanics, don't know/realize this and they mistakenly connect signal ground to the engine (as in a 1g). A typical example is when replacing the front O2 sensor and the harness connector/wires are damaged and need replacing. Connecting the O2 signal ground to the engine/chassis (or even battery negative) can cause misleading and noisy signals to the ECU causing the ECU to run the engine poorly. And if it is still also connected to the original harness signal ground wire, then all of the above engine sensors will also have that problem.

So unplug the ECU and if you still have continuity between sensor ground and chassis ground, you have a problem (usually a sensor's ground connected wrong).

 

[pindlepiper]

I will check with the ECU unplugged again tomorrow. So if i am getting continuity between sensor ground and chassis ground, could that possibly be why i keep blowing the engine fuse?

 

[luv2rallye]

Unlikely, but it's always best to keep things wired correctly.

 

[Ethans 1997 GSX]

its a short, but i had the same problem inmy old 420a that i sold.. i know this is bad advice, so im telling everyone on here this is a band-aid not a solution. if you put in a higher watt fuse, it wont blow. now this can be bad, because where the short is the higher watt fuse will create that section to be hotter. possiblity of a fire starting. the only way i would reccomend this is if your driving it to a shop for someone to detect the short.. sorry if i pissed anyone off

 

[pindlepiper]

Thanks for trying to help, but i "personally" would never do this. Luckily its not my daily and shes tucked away in the garage. Its just finding the time to find the short that seems to be the problem. Ill go out to the garage and mess with it for an hour or two and it just seems like i end up at square one. Maybe i need another set of eyes to look, it might be right in front of my face.

 

[pindlepiper]

So what all is hooked up to pin 92 sensor ground? I have four wires feeding into one at pin 92. Front o2, Rear o2, what are the other two? I believe one is MDPS? I cut each one trying to find the culprit. The last one left was the one shorted to chassis ground. I just cant seem to find what it runs to.

 

[pindlepiper]

Well I think i finally figured out my problem. Switched back to AEM EMS and the engine fuse was still blowing under a load. Figured out i had a short in the o2 sensor causing it to blow the fuse when it went to a constant voltage under load. Fixed problem and i have put over 100 miles on the car and shes still holding strong. Its nice to have boost back again!