Need help! Scanmaster reading crazy and running rough

2QWIK4U

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May 27, 2001
Car been running fine, get back in it and check engine light on and running rough. Smells really rich but scanner displays all 0s or really crazy #s but won't even cycle to the codes to see it. I swapped chip and maf sensor but no difference. I'm stuck and need advice ASAP ! Thanks!
 
what's the check engine light doing at key on, and with engine running?

Try another ECM? try it with the MAF unplugged?

B
 
Light stays on but it's odd it would go off but when it did the scanmaster would go off to! Unplugging maf had no affect at all. The scanner is showing everything maxed out
 
Car been running fine, get back in it and check engine light on and running rough. Smells really rich but scanner displays all 0s or really crazy #s but won't even cycle to the codes to see it. I swapped chip and maf sensor but no difference. I'm stuck and need advice ASAP ! Thanks!
You can do a search for " Weird O2 Readings " posted by Royal-T-LTD, his car had BLM's pegged at 160, had stalling problems when warm and had 000 displayed on his ScanMaster it ended up being a new O2 sensor (AFS-22) he installed. TurboDave says AC - AFS-20 is a better choise. Hope this helps, Kyle.
 
Unplug orange ECM wire by battery. Remove chip(s), check prongs, reseat chip(s). Reconnect orange wire and restart.
 
I've unplugged PCM,swapped chips and made no difference. What I've found so far is weird. I noticed with foot on brake that light went out and car ran better. Unplugged cruise switch at pedal and light went out and ran perfect! Why? But the scanmaster only lights up then goes off and won't display any data at all?
 
What all runs on the same circuit as the cruise switch? As I stated....with the plunger on cruise switch out the car runs fine and check engine light goes out. As soon as u push the plunger in the car starts running really rich and light comes on. The scanmaster will show 2.0 when u turn key on but quit displaying any data. Need some ideas.
 
Isn't there a big vacuum line on the cruise switch? Maybe it leaks until the brake pedal is pressed in? Clamp it off and see if that helps?
 
I've got the cruise switch unhooked and just laying under dash and car is running good but still no readings from scanmaster. If I plug up switch and press the plunger the check engine light comes on,car runs awful and scanmaster comes on but isn't reading correctly. It shows everything maxed out and coolant temp at -40. I'm stumped
 
there are several switches on the brake, what wire colors are on that one?

Something is backfeeding either power or ground to the ECM.

Do you have a voltmeter or test light handy?

Bob
 
It's the top switch, it's white and has the vacuum line hooked to it. I've got a voltmeter, not real good at electrical stuff but point me in the right direction if u can. The cruise hasn't worked in years anyway but still need to figure out why I'm not getting any scanmaster data.
 
I been thinking about this. How is the scanmaster hooked up? Ensure you are getting power directly from the fuse block instead of tapping another hot wire under the dash. Check the ground also, mine is on a ring terminal to the steering column. Finally check the connection to the ALDL and check that the wire doesn't have any bare spots on it that could be grounding.
 
I've got to report....so far,so good. Picked up a reman computer at Oreillys this morning and I think it's fixed. I wish I started it before I swapped them but didnt think about it at the time to see if it was still having the same problems. I've got to wonder if it just went bad or if something else shorted it out. I still would like to know where the vacuum line from the cruise switch on the pedal goes to under the hood.
 
Drove it around a good bit today and I think it's fixed. I guess the ECM just crapped out without warning,all the readings looked good and other than the pte oil feed line leaking a little no other problems right now
 
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