Engine Sensor Fuse Keeps Blowing
Engine Sensor Fuse Keeps Blowing So here in Illinois a few weeks ago, there was a ton of rain. I was driving in it, hit a huge lake of water, and killed my passenger O2 sensor. The engine sensor fuse blew out about 2 days later. I replaced the fuse but it kept blowing. Yesterday I replace the O2 sensor and the fuse, drove to work (30 miles) today just fine, but then when leaving the fuse was blown again. Any ideas what the heck keeps blowing this fuse? As usual, when the fuse goes out, the SES light comes on and throws the reverse solenoid code and the MAF code. Anyway, any help is always appreciated.
Mike
Mike
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Joined: Feb 2007
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From: Fairfield, Cali
sounds like you have a short to ground i would check the wiring to the sensors which fuse is the one blowing out? Get a schematic and track it down.. follow the fuse the one thats blowing.
I cannot seem to find any wires that are exposed. I know it has to be an exposed wire because when I replace the fuse it does not blow out right away. If I drive like grandma it doesn't blow out, but if I hit the gas once or twice, it does. I traced the wiring harness from the CPU to the passenger side O2 and I do not see anything wrong there. I've checked the driver's side all the way to the top of the engine bay and haven't seen anything yet.
I bought a mulitmeter to check the O2s and found that the driver's side is the only one without continuity. Two wires on the sensors themselves have continuity, the plug extensions for the O2s all have continuity, the passenger side O2's two wires have it, but the driver's side does not. So that is where I started following the wires. Nothing yet...This is horrible.
I bought a mulitmeter to check the O2s and found that the driver's side is the only one without continuity. Two wires on the sensors themselves have continuity, the plug extensions for the O2s all have continuity, the passenger side O2's two wires have it, but the driver's side does not. So that is where I started following the wires. Nothing yet...This is horrible.
passenger side in the middle near the shock tower. there are some wires that go straight down next to the frame. They are sandwiched by the frame and the headers. That is where you will find the burnt wires.
most of the time its on the driver header oxygen sensor, on longtubes they mount the hole facing out and the wires get cut on the heat shield thats right there, the best way is to take some tin snip cutters and cut a small piece of that heat shield,
i had a guy i did a cam swap for recently have the same porblem, after the cam install the engine shook some much untuned that the oxgen sensor kept cutting into the shield..
i ve ran into that problem many times, that fuse controls all four oxygen sensors if you have them, and MAF, and if m6 the reverse lockout i believe
i had a guy i did a cam swap for recently have the same porblem, after the cam install the engine shook some much untuned that the oxgen sensor kept cutting into the shield..
i ve ran into that problem many times, that fuse controls all four oxygen sensors if you have them, and MAF, and if m6 the reverse lockout i believe
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http://www.bmotorsports.com/shop/pro...roducts_id/556 -> We also sell the sleeving and teflon wiring separately for those who want to do their own wiring.
A common failure we see on poorly made extensions is abrasion and subsequent shorting of the wires to eachother or the header OR the wires melting internally so that you cannot see the failure until you cut the whole extension apart. Either problem can lead to intermittent shorts and blown fuses.
Every now and then we do see factory wiring short in some location or where a person didn't re-route the factory harness properly and it takes some time and patience to track down where that fault is. It can be VERY difficult to see the exposed (but often corroded) copper in such an instance.
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Verdad Gallardo Anyone have a wiring schematic for all the wires that the engine sensor fuse applies to? (Long shot, I know) I have torn my carp apart trying to find this stupid problem. I've checked all the wiring from the plug to the computer and cannot find a thing. I bought a used MAF to see if that will fix it, though I doubt it. Anyway, I am sure there is some wiring that I missed and do not know where it is. Any other ideas?
Try Helm, Alldata or Mitchell for the schematic. A fuse blows in two ways:fast(short) or slow(overload). Automobiles don't use slowblow fuses so you don't have to worry about that. Can you narrow it down to a short to ground: blows immediately as soon as power is applied-KOEO or after the load is applied-KOER? A short means a HOT wire has BYPASSED the LOAD and has found an easy path back to ground-NOT GOOD. An overload means the circuit is working for a while until the LOAD goes into OVERLOAD and blows the fuse-also NOT GOOD.
Former Vendor
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Anyone have a wiring schematic for all the wires that the engine sensor fuse applies to? (Long shot, I know) I have torn my carp apart trying to find this stupid problem. I've checked all the wiring from the plug to the computer and cannot find a thing. I bought a used MAF to see if that will fix it, though I doubt it. Anyway, I am sure there is some wiring that I missed and do not know where it is. Any other ideas?
You can try to test continuity between the heater circuit lines and move / handle the extension section by section and this may help identify where the problem.
It's not the MAF. I test that and the one I have is fine. I will rip the extensions out and check the wires.
The weird thing is that when the rpms are higher (above 2000) I never seem to have an issue. When I start to accelerate from a stop, that is when I have the most problems. I have to push in the clutch, get the rpms above 2000ish and then let the clutch out and the car goes. Same thing when driving at about 45 pmh in 5th gear. I hit the gas and it starts to stumble, then I put it in 4th and the car goes without issue. Is that an O2 thing, an MAF thing? I wouldn't think a bad wire would be so predictable. On the other hand it could be all in my head and it happens all the time but I just don't notice it. I'll worry about it on Monday, it's almost time to go to Mexico for a few days!
The weird thing is that when the rpms are higher (above 2000) I never seem to have an issue. When I start to accelerate from a stop, that is when I have the most problems. I have to push in the clutch, get the rpms above 2000ish and then let the clutch out and the car goes. Same thing when driving at about 45 pmh in 5th gear. I hit the gas and it starts to stumble, then I put it in 4th and the car goes without issue. Is that an O2 thing, an MAF thing? I wouldn't think a bad wire would be so predictable. On the other hand it could be all in my head and it happens all the time but I just don't notice it. I'll worry about it on Monday, it's almost time to go to Mexico for a few days!
So I got back from Mexico and tore the car apart again. I found that the wiring for the plug that goes in to the tranny, directly above the starter, was exposed and frayed. I cut it and connected it back together using one of those little wiring clamp things (w/e the hell its really called.) I taped up the wire with some electrical tape that is good for about 200 degrees of heat. I put everything back together and drove the car about 10 miles and then had to replace the fuse but I then drove another 100 miles without issue. Then, it came back. The car acts the exact same way and the fuse blows every 10 feet I drive. I was so excited when I found that wire (no clue what it is actually for, my guess is the reverse selenoid since it plugs into the tranny 
) So I got about 100 miles of happiness out of the car and now I am back to the misery. Kill me. 
) So I got about 100 miles of happiness out of the car and now I am back to the misery. Kill me. 
The ground near the starter is good and the one that the drivers side O2 is attached to (in front of the fan) is good. Not sure about any of the ones attached to the heads themselves.
There are 2 or 3 grounds(can't remember off the top of my head) on the back of the cylinder heads. Check those to make sure they are still tight
What causes a fuse to blow? It means the LOAD(motor,sensor,lite bulb,etc.) has been BYPASSED and the HOT wire has found a shorter path back to ground(short circuit). At this point you need a schematic. I would use AlldataDIY.com to get the info you need. For $17 you get the entire manual online for a year. I buy them all the time and they're worth it. Since you know the fuse that is blowing you have to follow the schematic from the fuse that is blowing to every junction point(connector) in the circuit. You unplug every connector(not just pass-through connectors, but the ones that go to devices[LOAD]as well) and I mean every connector on that circuit. Now put in a good fuse. Does it blow? No-start plugging connectors back together one at a time until it blows. You may have to jiggle the wiring harness during this process to get the fuse to blow and narrow down the area when the problem resides. Once the fuse blows concentrate on that area looking for chaffed or pinched wires or bad insulation. You might even find the bad wire while looking for the connectors. Does it blow? Yes-Murphy's law just got you. This means the short is between the fuse and the first connector. Not the easiest to find, but at least you know where to look. You need a Fuse Saver. It's made just for this job. You plug this thing into the fuse socket that is blowing. It has a circuit breaker instead of a fuse and it "BEEPS" when the breaker trips. A Fuse Saver would help you to find this problem or at least get you in the ballpark. Good Luck. You'll need it.
just had my eng sens fuse keep blowing and this was the problem. couple of the wires in that harness melted.