Hello,
On my 86 trans am, the SES light comes on as its supposed to at start up, sometimes goes on while driving. The car runs well. I wanted to see what code it was throwing so i used the wire jumper trick first, no result. i then hooked up my Innova OBD1&2 scanner, which has worked perfectly on other obd 1 and 2 cars and is supposedly compatible w/ GM.
The scanner reads "no communication w/ ecu". I tried it with ignition off, on and running.
I saw on a website there was a TSB for this problem on 1986 cars, but couldnt get the details.
Is it a bad connection or a prob with the ECU?
anyone have a link that shows the full TSB?
thanks

 

ok, the TSB was for a '96 not '86
can i test the ALDL port for ground or voltage?

 

I believe you need a 4K resistor on the std cable to connect to the CCC systems.
Can't get to the diagram from where I'm at or I'd link you to it.
Do a quick search for the std cable diagram. It shows the resistor that is used for carb applications.
HTH

 

You'll have to talk to Innova on the 4K resistor issue. My Autoxray works fine on my '84, '85 and '87 carbed ECMs. Got the scanner configured for the right year/Vin? Correct cable?

Easy enough to test continuity to ground for the ALDL ground pin with a test light or meter.

 

OK, it was 1.5 K resistor but was called R4.
See here and test if your cable has it.
http://winaldl.joby.se/aldlcable.htm

 

Ill have to check w/ innova, but it does say in my manual that the supplied GM adapter is supposed to work. Ill check the ground on the plug.
Im pretty sure the prob is with the ALDL. I should get some voltage readings from other pins too, correct? Im pretty sure its the connection since the jumper wire trick didnt work either. I mostly started this thread because i thought there was a TSB for this prob.

Naf-does your autox-ray work on the efi cars of the same years w/ the same adapter as the carb?

 

Yeah. My autoxray has worked on a couple TPI and TBI cars that I've connected to, as well as later model stuff. Hasn't failed me yet. If the paper clip trick didn't work it's likely your ALDL. I've heard that the connector is prone to lose its ground but have no personal experience of this ever happening.