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Blowing the ecm fuse on a 94 Sub

retroblazer

retroblazer

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Out of the blue, I had a fuse blow on my trip from Los Angeles to Chicago last week. It was the first time the fuse has blown and it has happened two times more since I've gotten home. It seems to go at slow speed or under acceleration. Also, I'm getting a service engine soon light coming on intermittantly. I had somebody read the code and told me that it was a "engine speed" problem. They used a Snap-On reader. Any ideas?
 
Not sure if this will help you or not but I kept blowing either the ECM or the ECMB fuse in my 87 Blazer when the fuel pump died. It would run for a few minutes then die and the fuse was gone every time. Changed the fuel pump and all was well. Just a suggestion...
 
Thanks for the note. You'd think the fuel pump fuse would blow rather than the ecm one. I had just replaced my fuel pump five or six months and about 8000 miles ago. So I'm a little reluctant to swap it out.
 
Sorry, off topic, but didn't you do a SAS on a Suburban? If so, do you have any pics we (I) could see.

On topic, GM runs a whole bunch of wires together in the harness. I believe it's orange wires that are hot all the time. Not familiar with the ECM B circuit enough to know if that's the "hot at all times" circuit, or the IGN fed hot circuit, but almost all engine sensors tie into the same wires. I'd look for any areas the wires may be rubbing on something or have gotten hot. Engine Speed code would lead me to start with wires going to the VSS.
 
bluejeep said:
Sorry, off topic, but didn't you do a SAS on a Suburban? If so, do you have any pics we (I) could see.

On topic, GM runs a whole bunch of wires together in the harness. I believe it's orange wires that are hot all the time. Not familiar with the ECM B circuit enough to know if that's the "hot at all times" circuit, or the IGN fed hot circuit, but almost all engine sensors tie into the same wires. I'd look for any areas the wires may be rubbing on something or have gotten hot. Engine Speed code would lead me to start with wires going to the VSS.
Click to expand...

What is the VSS?
 
Yes, I did SAS on my Sub. I'll see if I can't get some pictures up. I would tell you that it has worked out pretty well. The only problem or issue that I have is that the bumpsteer is pretty dramatic. I will be putting a track-bar on shortly. So far, I have prerun parts of the Baja 1000 and most of the San Felipe 250. I even pulled a buggy out through twenty miles of soft sand in a whooped out wash with no problem. I'd like more front wheel travel still, but for what I built it for, pulling my race Blazer if it breaks in the remote sections, it's great.
 
VSS is Vehicle Speed Sensor. Since yours is a '94 it'll have the 4L60E so I don't know if it has a DRAC module or not.

I have a '99 Suburban that I've considered doing a SAS on. Wondering how it would do for DD and towing duties, as I don't want to ruin a perfectly good truck. What size tires/gear ratio are you running? Thanks.
 
A 99 is too new to be hacking. Not that mine is hacked, but for what you're using it for I'd really think about it.Mine had a 150k hard miles on it and was really used up. I ended up with a d44 up front and a 14bb in back with 4.88 gears. The brackets in front add three inches of height and I used a set of Deaver 4" lift springs. In back, when I added the 14bb, I moved the front mount of the rear spring forward and a shackle flip kit from Watson, reversed by side and used the longer pickup truck springs with three inches of lift from one of his suppliers, maybe Tuff Country. The front has double 12" 5150's from Bilstein and single 5150's in back with Bilstein bumpstops. The back work great, smooth and lots of flex, but the front is a little stiff. Not too bad. That's the difference between 60" springs and 48", plus the extra shock. I also have ORU's swaybar in front with Watson's crossover steering. In terms of a daily driver, it's too tall. The door sill is the height of my pants inseam, 34". I know that 7" of lift doesn't sound like much, and the 35" BFG All T's aren't that big, but if your Sub is being used as a mommy wagon, you'll be hearing about it everytime she makes a trip. As far as towing, I haven't really had to use it for that purpose, but I did put a hot 383 in it, so it should do ok. I'm getting about 9+ mpg. The brakes are really good. I have the twin piston 3/4 ton Fords on front and Chevy discs on the back. So on second thought if you limited the lift to 3" and 33's, it would work.
 
Great info, thanks!

My sub has 185K on it, which would make it easier to hack. Height is kinda what I was concerned with, as it does see mommy wagon duties on occasion. I was going to shoot for 4" of total lift with 35" BFG's (H2), and the same axles as you. Guess I'll just wait for the pics and see, sounds like an awesome truck!
 
Blowing fusing

It's blown again. Would take this to a dealer to sort out?
 
You don't, by chance, have (or have access to) a factory service manual for the Suburban do you? The wiring schematics should show all the components that are tied into that fuse, either directly or indirectly. From there you could trace wires and look for potential issues.
 
retroblazer said:
It's blown again. Would take this to a dealer to sort out?
Click to expand...

I'd buy a service and wiring manual for your truck before I spent $1 (well, $75/hour?) on a dealer looking at my vehicle.

'94 is going to be wired quite similarly to any '88-95 GM TBI truck I'd suspect, perhaps enough to get you close if you can't find your exact manual.
 
Factory service manual

Any idea of what they cost or if there is a specific manual that I should order?
 
You can head over to helms.com(?) and likely buy them brand new. Sometimes they have $30 sales on some of the manuals.

You'd want to get whatever is applicable to your 1994. It seems that the GM stuff either came in two or three volume sets. Service Manual (how to fix the truck components like engine, axles, transmission, etc., plus driveability and emissions) and Electrical, or in some cases, seperate Service Manual, Driveability and Emissions, and Electrical manuals.

ebay is also a good place to go sometimes, but the 1994's might be kind of hard to find based on how "new" they still are.

GM's service manuals used to be labeled something like "ST330-86" on the front cover, which indicates the year as the last two digits, but not sure if they still do the numbering that way. Had to be careful that your specific truck was covered, both the S10 and C/K stuff were titled "light duty truck" at one time. Also had to watch for "early releases" of manuals, as they did exist as well, at least at one time, and didn't have all the info in them as the "real" manual for that year. I have a feeling thats something you'd only find on ebay though, not helms.
 
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