my 89 c4 vette is having problems.. and the service engine light comes on and off very frequently.. so i have a friend who is good with corvettes who tried to figure out the problem.. he has an obd1 scan tool that he tried to hook up to the ecm but the problem is even after he hooks it up the scan tool says "waiting for connection" which basicially means that the scan tool is not able to communicate with the ecm.. my buddy tested the serial connection for continuity and he says it is fine.. so he told me he thinks the computer is shot.. what do you guys think is the problem.. if the computer was shot wouldnt the car not work at all?
i am hoping that maybe it is something small that can be fixed.. because i know if he could get this scan tool to work that he would be able to adjust all my parameters and get the engine running good again..
any help or input is much appreciated.. it is killing me that the vette is not running well..
yea i checked that thread out.. so basicially you do think my ecm is shot then?
Your symptoms seem almost exactly like his. Before shelling ot the $$ for an ECM...see if youcan borrow one from a friend...any Corvette or F body ECM from 86-89 will work. Just remember to put your MEMCAL in the ECM when you swap it...especially if using one from an F body.
I have a '165' ecm in my car. This ecm was used from 86-89. I converted from the '870' ecm.
Put a paper clip between pins A+B and turn the ignition switch on but do not start the car. The engine light will flash once, then twice (which means code 12). It will do this 3 times then it will flash any stored codes then end with three code 12's.
Post the stored codes and we can tell you what they mean.
I don't know what your scan tool needs to work. The 165 ecm needs a 10k ohm resistor to send data to scanning software (Winaldl, Tunerpro, Datamaster). Check with the maker of the tool.
To pull the codes, you don't need a scanning tool other than a paper clip.
Do all codes disapeare after disconnecting the car-battery or are there old codes in under to pic up with more sophisticated tools ?
Thanks ! Hebbe / Glad finding this thread ! Been wondering about how to pic up the codes for a long time.
my 89 c4 vette is having problems.. and the service engine light comes on and off very frequently.. so i have a friend who is good with corvettes who tried to figure out the problem.. he has an obd1 scan tool that he tried to hook up to the ecm but the problem is even after he hooks it up the scan tool says "waiting for connection" which basicially means that the scan tool is not able to communicate with the ecm.. my buddy tested the serial connection for continuity and he says it is fine.. so he told me he thinks the computer is shot.. what do you guys think is the problem.. if the computer was shot wouldnt the car not work at all?
i am hoping that maybe it is something small that can be fixed.. because i know if he could get this scan tool to work that he would be able to adjust all my parameters and get the engine running good again..
any help or input is much appreciated.. it is killing me that the vette is not running well..
I just went thru this same thing with my 89 with auto. It was a bad ECM. The Chevy dealer charged $150 for the ECM plus labor. I had no codes either and the exhaust smelled like it was running really rich when the SES was on.
Should be around $100 from NAPA etc. I would not buy anything electrical off EBAY, or anywhere else where I could not return it and/or get at least a 1 year warranty; which is what I believe you get from NAPA for an ECM.
Electrical items that you buy and you install are gauaranteed until yoiu walk out the door. This is the policy of almost every parts dealer. Electrical items atre guaranteed when they atre installed by a repair shop. This policy is usually posted in all the parts houses that I have ever been to.
Electrical items that you buy and you install are gauaranteed until yoiu walk out the door. This is the policy of almost every parts dealer. Electrical items atre guaranteed when they atre installed by a repair shop. This policy is usually posted in all the parts houses that I have ever been to.
mrmuzic
Not the Carquest I patron. As long as I have the receipt they honor the warranty implied on the receipt. My ECM had a 1 yr warranty.
Corvette Store
Scan tool won't communicate with ECM
about how to pic up the codes for a long time. 
