Codes

I have an 89 Blazer Full size. The codes were 37, 38 and 12 Dose any one know what they are. The service eng light comes on priodicly but not constanly. Please help thanks

I'm not finding anything for codes 37,38 in gas motors...are you sure those are the right codes or is this a diesel?

I'm not finding anything for codes 37,38 in gas motors...are you sure those are the right codes or is this a diesel?
Thanks GM I found what I was looking for. Bought an old Manual from a friend. Now if I could just read through the grease to find the torq specs for the heads I'll be in good shape.