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Topic: Diagnostics Scanner

in Forum: C4 Engines

Diagnostics Scanner (1/3)
 11/5/20 5:05pm
Wayne H.
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Sandown, NH - USA

Vette(s):
1985 Blue Corvette Coupe


Joined: 9/23/2020
Posts: 2

I have a 85 coupe with the L98 that is acting awful since replacing the battery.  I would like any recommendations for a scanner to do some diagnostics on what may be wrong with it.  It won't run for any length of time, so I can't take it to someone to read the codes.  When I try to get them with the paper clip jumper method, I just get a steady check engine light.  No flashing.  I am new to the forum, but it looks like many of you have had problems that others have seen before.  The scanners that I have seen online like the Actron CP9690 seems to be able to connect to the OBD1 with the adapter, but reading some of the reviews it sounds more like it's a hit or miss.  I also saw the Innova 3120RS which says the same thing.  Has anyone found one that will work?  Hope you can shed some light on this.

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Re: Diagnostics Scanner (2/3)
 11/5/20 9:36pm
Adams' Apple
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Duncanville, TX - USA

Vette(s):
1985 Coupe-L98/Auto,Bright Red/Carmine. 1974 Coupe-L48/4speed, Medium Red Metallic/Black Deluxe.


Joined: 3/18/2009
Posts: 2157

Sometimes disconnecting thr battery will clear all of the ECM's "learned" values, making the engine runs rough, or not all all for a while. The ECM needs to "relearn" all of the basic settings to keep the engine running properly....idle speed, timing, etc. Most of the time, just letting the engine idle for 30 minutes or so will correct the problem....assuming of course, that it was running properly before the battery swap.

Using the paperclip jumper method at the ALDL(assy line diagnostic link) connector will work 99% of the time. Make sure the key is OFF when inserting the jumper. Jump the A & B terminals, then turn the key on. The "Check Engine"(or "Service Engine") light will flash the engine codes IF any are present. A flash of "1...2"(one long flash followed by 2 shorter flashes) indicates no codes are stored.

If the jumper deal doesn't work, you may have an issue with the ECM, or the wiring at the ALDL connector. Before spending any cash on a scanner, or code reader, make sure there is a good ground on the "A" terminal on the connector, and 5v on the "B" terminal. If you don't have both, a scanner/code reader won't work either.

ALDL connector

 

There are many cheap code readers out there. I can't speak for any of them as far as which one is best for your purpose. It just needs to be able to work on pre OBDII systems. I have 2 Crap-On scanners, a Launch CR Pro, and an OTC Monitor II that I use on a daily basis....none of them were cheap. All you really need is something that will pull codes, and possibly show the limited data available on the L89 system. Having access the data is always helpful.

 

 

 




 



|UPDATED|11/5/2020 7:36:17 PM (AZT)|/UPDATED|


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Re: Diagnostics Scanner (3/3)
 11/6/20 11:03am
Wayne H.
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Sandown, NH - USA

Vette(s):
1985 Blue Corvette Coupe


Joined: 9/23/2020
Posts: 2

Thanks for the feedback Adam.  The car has always been garaged, but before the battery replacement not run in about 12 months.  I have noticed several connections on relays and sensors have been covered in oil from valve cover gasket leaking, so I picked up some electric contact cleaner and will get them cleaned up as well as new gaskets for the valve covers.  I will also replace the fuel filter, and I'm looking into finding an injector cleaner tool to rule them out after sitting that long.  I did drain the fuel tank and put fresh gas in it, but the old stuff was probably still in the fuel lines and rails.  Anyway, I will check the pins of the connector for ground and voltage before trying the jumper again to read the codes.  Thanks for your help. 

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