I live in one of those areas that requires emission testing. Today my 1994 IDI failed because the "check engine" light won't light. Exhaust opacity is low and the truck seems to run fine. I actually don't remember having seen a "check engine" light on this truck ever light up, but Colorado failed it because of NO light. I pulled the instrument cluster to check the bulb but no power at the bulb. Before I get in over my head, can somebody steer me in a diagnostic direction? I assume checking the ECM would be in the works, but I'm not even sure what it actually does in this truck given that it has a ZF-5 manual. Thanks in advance for the help.