SM numbers going nuts and another concern...

Welcome!

By registering with us, you'll be able to discuss, share and private message with other members of our community.

SignUp Now!

Bescurred

BOOSTED SHAMU v2.0
Joined
Jun 10, 2001
Messages
1,580
I just wired up my SM, it's pretty old like about 10 years and its the 2.1 v. At first the numbers looked normal. Then I get it up the street and all my numbers start bouncing all over the place once second it will show 40mph next 244 or something crazy. All my numbers are doing this so I'm not able to tune it. Power is coming from the fuse panel and I got a good ground. Is the Scanmaster just bad? Is my wiring job jacked up?

Also I changed the oil and as I get done I crawl under the car to do a leak check. While the car is running I see something drip. Real small. I investigate it more and I look up under and see little bubbles coming from where the turbo mates up with the exhaust manifold. Very slight puffs of white smoke coming out the exhause but once it warmed up I didn't see anything. It's been rainy here and the car has sat for about 6 months before I just started to drive it. So I don't know if its condensation somewhere or a bad headgasket thats just leaking into the exhaust side. Is that even possible? Oil and water are not mixing at all.
 
Check your connection to the ALDL port. If the car runs fine, its probably the SM or its connection.
Most likely condensation at the turbo if it has been sitting and its damp out. Double check your oil and coolant level.
 
Thanks man,

Anybody else have an opinion on the turbo issue? That's my biggest worry,.
 
Thank ya baby jesus!!! It did go away after the car was at normal temp
 
I messaged the man him self Bob Bailey and apparently the low fan relay is the problem. I unplugged the relay and readings went normal hmmmmmm. Just a heads up for future issues that might come up.
 
Wow. Thx for the answer.. would.have never saw that solution comming.lol
 
the issue is this:

the ECM sends the datastream and the fan relay control thru the same driver chip. The channel it uses for the relay is a PWM (pulsing) channel, and the relay kicks back a voltage spike on every pulse when the fan is commanded on.

The chips in some of the ECMs let the kick-back pulse bleed thru into the datastream, thus corrupting the data.

Some ECMs are more susceptable, some relays create a bigger spike, etc....

The Scanmaster has a filter on the data input to absorb the noise.

So, its possible the noise filter is not working in your scanmaster, or your ECM has an issue or the relay is not properly suppressed (there is a resistor inside the relay)

But at least we know whats happening now.

Bob
 
So what should I do next? I know the car has had some ECM issues...do I need to just get a new relay try that first since they are cheap?
 
Try a relay first...i hope its not the fan....your voltage droping alot when come on? That would be another sign of bad fan or battery/alternator/wiring
 
The fan is acting goofy right now...that's another issue I gotta get to later. The previous owner cut the middle wire from the harness side and spliced it to the lower side of the resistor on the fan.
 
UPDATE:

The fan relay turned out not to be the problem...it was really an odd issue and at first it seemed like unplugging the low fan relay it cleaned up the signal to the SM.

That was not the case. I ended up sending the SM back to Bob and he had to do something. I think the paper work said something along the lines of wiring in something that would cut out interference to the SM. Bob fixed it for free and even put my SM into a new box since the old one was kinda beat up. So I basically got a newer looking SM for free. I've driven the car about 400 miles and the SM is right on!

Thanks a lot Bob!
 
In line with these issues, I have wired my dual ( Concorde) fans the old way with separate hi & lo switches! Can be a pain sometimes but I feel it has no way of contaminating the factory / relay system. Bypassing the factory settings and / or allowances I feel comfortable.
Have I missed something??
 
Back
Top