How can I check the codes on a '90 GMC Sierra?

rms-man · October 13, 2005

The SES light comes on at times and it looks like an OBD I setup under the column. Is there a sequence to follow using a jumper wire or something to get the codes out of it? Also, is there a breakdown list for these codes?

Thanks,

Joshua

rms-man · October 20, 2005

Okay, I used a paper clip and jumped the terminals. After the code 12 it gave me a code 32. Can you tell me what this code means? Thanks.

Joshua

GM-Tech · October 13, 2005

The SES light comes on at times and it looks like an OBD I setup under the column. Is there a sequence to follow using a jumper wire or something to get the codes out of it? Also, is there a breakdown list for these codes?

Key on, jump between terminals A & B. Without looking at it, I can't tell you which is A & B, but as I recall, they're the only two right next to each other at one end of the connector. You can use a paper clip or whatever will fit.

The light will begin to blink. It'll go BLINK (pause) BLINK BLINK. That's a code 12. It'll blink that code 3 times. A 12 is just the computer saying, I'm alive and capable of displaying codes.

After the 12, "real" codes will display in the same manner in. When the last real code has displayed three times, it will start on 12 again and you know your done.

There's probably a list of codes somewhere. You can post 'em here and I can tell you what they mean.

Jerther · October 20, 2005

Code 32:

Exaust Gas Recirculation Failure (EGR)

Check the vacuum source and all the vacuum lines. Check the system electrical connectors at the ECM and EGR Valve. Replace ECM or EGR Valve as necessary.

Took from my Haynes repair manual.