Scan Tool for 87 4cyl RECOMMENDATIONS (Page 3/3)
Mickey_Moose APR 15, 02:20 PM

quote
Originally posted by Patrick:

Just in case there's any confusion here... Scan tools and/or scanning software used with Fieros do not have the ability to adjust ECM parameters. They simply display in real time what the various engine sensors are reporting to the ECM.



This - the only way to change any parameters of the Fiero code is to use Tunercat and an EPROM burner. It cannot be done on the fly - EPROM has to be removed, erased and reprogrammed.
FX APR 15, 02:55 PM
All very interesting ogre, and enlightening...Thanks...
Chic_in_a_mask APR 16, 03:29 AM

quote
Originally posted by theogre:

Sorry...
ECM Scan Tools often Will Not tell you what's wrong but often still needed just to check several things and more so w/ 87 and up Dukes because 1227748 ECM includes Cruise logic builtin to the board.
Examples:
  • Dash gauges often are way wrong for many cars not just Fiero. ECM is more accurate for engine temp but ECT can lie too. Quick Check, When the engine is cold ECM should read ECT close to weather/garage temp where parked that day. (Side note: Most older GM cars had same Temp dash gauge but w/o numbers because numbers are often wrong.)
  • You have measured Volts at the battery etc and think Volts are same all over. You are Often way wrong. Worse, ECM sees Low Volts for iffy grounds power or both for any reason then you can have "hunting idle" problems etc. Is part of why ECM reports Volts as data to read w/ a scanner. IOW You measure 14.6 at battery w/ engine running but ECM reports "I sees 12 or lower volts" then you have problems including maybe an iffy ECM.

    But Reading Engine Timing and some other things are fairly useless even for experts because data stream is way to slow and numbers are all over the place even when that are perfect. Example: Reading O2 volts or rich/lean mix are fairly useless when the engine is warm/hot but seeing "O2 ready" flipping yes/no under same conditions is trouble most times but may not be O2 sensor itself even when ECM sets "Code 13." Many see "one wire" O2 and never bother to check O2 Ground (Tan wire for Many GM models) bolted to the block somewhere that's often have problems.

    Is not unique to OBD1 either. OBD2 scanners say Pxxxx is the problem, say 1 of several O2 sensors in new cars, means to most users = that sensor is bad but often is not and still replace it anyway and often bill Hundreds of $ because many O2 are high $ parts. Many Aftermarket O2 start at ~ $150 and go much higher. Then car is back in next few days or few weeks w/ same DTC because most ASE can't look for the real problem like a weeping intake leaking coolant into the engine and poison O2(s) and often the cat(s).

    See my Cave, Scan Tool Help and the rest of section. Then Wiring section as well.




    • The more info the better, and ever since I have found your site I have been reading everything you have on it. Thanx TheOgre! Like I told Patrick I know this topic has been over done already but I am new to this forum and have not seen any post specific to my need. I really appreciate everyone putting in their part in my post. I did find the culprit to my fan issue. I had a short from the fan to the ECM, do to the abundance of rats here in Hawaii that love living in cars that sit for too long. Everything is now running tip top! Thanx again gentlemen for all your help!

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