One problem related to emission control has been reported for the 1997 GMC Sierra. The most recently reported issues are listed below.
Loose body bolts;repaired by dealer. Had evo sensor replaced at a chevy dealer since they knew about the problem that affected this new feature, electronic variable orifice was new in 1997. The truck was dangarous to drive, felt like a go-cart, all over the place. They chevy dealer also burned in a new program for mixtures and timing went they replaced both O2 sensors and cleaned the egr valve. Did I pay to replace these items due to a bad program?? I think I did. What is warrenty on emission system from the manufacturer. ???.