ECM and O2 Sensor fuses keep blowing

[kpv]

I am having a problem with my VX. My “Check Engine” light came on a while back (about 6 months ago). I ran the codes and it showed 3 of my O2 sensors had issues. I purchased 4 new O2 sensors and then procrastinated installing them. Finally, the other day, I pulled the VX into the garage and went to bed. The next day, I went to start it and it just turned over without a hint of wanting to start. A little diagnosis revealed two blown fuses. The fuses were the 40A ECM (box-type) fuse and the 20A O2 sensor (regular type) fuse. I decided it was high time to replace the O2 sensors. I did this and what a PITA the right front one was as the electrical connector is located on top of the transmission bell housing. Well, after some ingenious installation techniques, I got it together and they were all done. I then replaced the two fuses as mentioned earlier. I started the VX and it sat and idled. After it warmed up, I went to move it by placing the transmission into reverse and it immediately stalled. Upon review, the same two fuses blew.
I then proceeded to change those two fuses several times with similar results.
In addition, I found when I replaced the 20A fuse followed by the 40A fuse, I would hear, what can best be described as, a whirring sound emanating from what I believe is the thermostat housing at the top front of the engine. I am not sure if that is the component as the fuses blow quickly which doesn’t allow me to seek out the source. This happens with the KEY OUT OF THE IGNITION!! In any case, the VX is immobile until I can get this resolved. If I can’t get this resolved, I will need to flatbed it to a shop. That will be a big expense.
Does anyone have any idea what is going on here? I did a search on the forum for ECM and came up with nothing of value. I recall there being harness shorting issues. Could this be the problem? If so, where do the harnesses typically short out?
Any help would be appreciated. Thanks in advance.

[SGT.BATGUANO]

If you're blowing a 40 amp fuse, I'd start looking for a direct short or pinched wire. Make sure 02 sensor or other wires are not hitting hot exhaust pipes or rubbing against sharp metal.

The wiring loom problems are in the driver side headlight area. Check the loom/ wires for abrasion and bare copper.

Did you do any electrical mods, upgrades or accessories that might be tapped into these fuses?

Have you had any body work done or screwed anything into metal that may have pierced a wire or wires?

Lastly, do you have any known bad components (like a trans mode switch) that may help further diagnose the problem?

If you already replaced your mode switch , did you fill the connector(s) with protective insulating grease to keep the contacts safe from the elements?

Mode switches have been shown to cause wierd problems when they go.

[Green Dragon]

The wiring harness inside the driver’s side fender rub and short out, usually causing Transmission Mode switch failure but in your case may be affecting O2 sensors & ECM

Further if 3 of 4 O2 sensors were indicating problems, I would look at the other end, that being the MAF Sensor- Air Filter- incoming air.

HTH
Bob

[kpv]

Can someone please post a picture of exactly where I need to look for the harness short behiond the driver's side headlight??

[kpv]

OK, the latest and greatest.

I got the VX running, HOWEVER, now 3 fuses keep blowing.

The first is the large, box type, 40A "ECM" fuse in the engine compartment fuse box.

The second one is the "O2 sensor" fuse in the engine compartment fuse box.

The third, and newest discovery, is the 15A "Engine" fuse in the passenger compartment fuse box.

The VX starts and will sit and run for as long as I let it. As soon as I get in it and drive it, I can't get farther than my driveway and it stalls and blows all 3 fuses.

While it was running, I moved around all of the harnesses in the engine compartment that I could reach thinking that if one was frayed, it would short and stall the car. Nothing happened, it kept on idling.

Besides just replacing all 4 O2 sensors only days ago, I replaced my mode switch a few months ago and that fixed the "clunking" gear changes in the transmission. Could the mode switch be bad AGAIN!!!!!?????

There is a little adjustment on the mode switch and when I installed it, I just bolted it up and the transmission worked great so I didn't move the switch one way or the other and left well enough alone. Should this be adjusted? Is it related?

If anyone has any ideas, I would greatly appreciate it.

[thebear54]

It sounds like to me that you have a massive short, possibly inside the center console area(if the only time you blow fuses is when you attempt to put the VX in gear)or wires coming through the hump. My advise(although time consuming) would be to pull the center console to check the wiring harness.
Good luck
John

[kpv]

Can someone PLEASE post a picture of the area of the harness that is prone to shorting behind the left headlight????? I looked there and pulled all three harnesses away from the body and they look perfect.

Has anyone had any issues with the engine bay fuse box having a short????

[Cyrk]

http://www.vehicross.info/forums/sho...ghlight=Frayed

From Anita:
The one that Im referring to runs just right of.... shoot...I dont know the name of the parts of the engine. Its to the right of the engine, about halfway back. Wrapped with black tape...

But yes, several owners including me have had experiences with that particular harness as well.

[kpv]

Cyrk,
Thank you so much for the picture! I jiggled that harness when the car was running but didnt do anything further with that one at the time. I thought you guys were talking about the three harnesses that are immediately in front of that one (about 4 inches more forward) that actually clip to the radiator support.

Where along the one that you are pointing to have the shorts been found??

[kpv]

Cyrk,
I also read your other thread but wasn't sure what the final outcome was for your problems. Was it the EGR valve? A short? Something else? Please recap what the final problem turned out to be on your VX.
Regards,
Ken

[Cyrk]

My VX was throwing tons of codes at the time, we replaced the TP sensor, P0123 (TP Sensor Circuit Input High) & P1121 (TP Sensor Circuit Intermittent Voltage High), my MAP senor an a Mode range selector switch, That cleared the codes then got another code and we could not find out what it was ands the only other thing connected to those items in some way was the EGR valve, replaced it and have not had another code since...

[Tone]

I have started using (and offering) a new product called ScanGauge that has history tracking, does not require a PC, and simply pplugs into the ODBII port - all for $125.00 http://www.scangauge.com/

Reads Trouble Codes
* Reads conditions that set the Trouble Code
* Clears Trouble Codes
* Turns off "Check Engine" light
* Make and store up to 10 rewritable special codes
to send to the vehicle computer

AND

Shows 4 gauges at a time from the possible following:

* Fuel Economy (MPG)
* Fuel Rate (GPH)
* Battery Voltage
* Coolant Temperature
* Intake Air Temperature
* Engine Speed (RPM)
* Vehicle speed (MPH)
* Manifold Pressure
* Engine Load
* Throttle Position
* Ignition Timing
* Open/Closed Loop

AND

Automatically tracks three sets of trip data -
Current (short) Trip
Days (total) Trips
Previous Days Trips

* Maximum Speed
* Average Speed
* Maximum Coolant Temperature
* Maximum RPM
* Driving Time
* Driving Distance
* Fuel Used
* Trip Fuel Economy

[Ruflyf]

The wiring harness inside the driver’s side fender rub and short out,

Green Dragon or anyone who has experienced this know whether its a short to body frame or from 1 wire to another within the harness? I have had a problem lately blowing the 40a ECM fuse whenever the vx got jarred vertically. Anyway this morning I got to jiggling wires under the hood and sure enough the harness that is mentioned behind the drivers side headlight is the culprit. I looked it over real good and didnt see any immediate signs or a short, so does anyone know if the short historically has been from wire to wire inside the harness or a wire rubbing through the insulation to the frame? Figured I'd ask before I start tearing into the harness and inspecting each wire.

[Anita]

My short was from a wire within that harness. The mechanic said it was a bee-otch to get to.

[Ruflyf]

thats what i was afeid you were gonna say. Oh well 90% is finding the problem, 10% is fixing it. Thanks for the info.