Jim Hannon

I have a 1986 Corvette and when I try to pull codes useing a paper clip the service engine soon light does nothing, it just stays on. I can hear the electric fan come on but no flashing. How can I tell if the OBD1 is working? If its not working is there any way to fix the problem? When I bought the car it had been rebuilt is there any wiring diagrams on the OBD1 plug so that I can be sure that it's wired correctly?

John A. Marker

You should be inserting the paperclip into the A & B terminals. These are at the top of the plug (as you look at it sitting in the seat) the last two on the right side

Jim Hannon

That is what I did and nothing happend just the electric fan came on the service engine soon light does nothing it just stays on. Should I be using a 10Kohm Resistor or a paperclip?

Benny42

Paper clip.

Jim Hannon

I tried the paper clip as I've done on other cars but the "ses" light comes on and will not blink even to indicate a 12 code. The fan starts like it is going to go through cycle but then the fan stays running but no code displayed.

coupeguy2001

sell it

vette079

Is the light on when you turn the ignition on, engine off (without a jumper)?
If yes, turn off ign, disconnect connector B at ECM, if ses light is on when turning on the ign, you may have a short to ground in circuit 419, wich in my 91 is a brown/white wire from terminal B1 from the ECM to the ses light.
If ses light is off, jumper terminals A-B on aldl, and connect a test light between ECM connector terminal B3 and B+.
If now the test light is on, check memcal for proper installation, if OK, replace ECM using original memcal.
Recheck code 12.
If test light off, check for open in aldl diagnostic terminals A-B, repair as neccesary.

Remember, this is from my 91 FSM, so wire colors or circuit numbers might not be the same.

When I hooked up my autoxray to my 91 the first time, nothing happened.
I found out that (one of) the small terminals in the ALDL connector were pushed backwards in the ALDL connector, this you can also see as an "open".
Check the terminals in the ALDL, and if possible, like I did, try to hold the wire and terminal at the back of the ALDL when you push in a jumper wire.
If you didn´t buy the car new, you don´t know how many people/times have been using the ALDL, with obvious results.

Steel Blue 91

Since "A" is the ground, I'd first try to ground "B" to another ground source. Run a length of wire from B to the negative post on the battery. If it works, then there might be a problem in the ground on the ALDL lke vette079 said. If not, check the terminal at the B location.

tblt44

Sound like you are going into diagnostic mode.
Are you sure you on the right terminals