93 GMC Jimmy service engine light

Someone can. Just about anyone with a scan tool can probably tell you what caused it. No one else can, just from what you've provided.

Some common causes from that vintage would include the 02 sensor. I'm not sure if 93's looked at the gas tank pressure or not. You might want to make sure the gas cap is on properly and completely.

Your best bet is to get the codes read.

93 is not OBDII compliant. Only cars late 95 to present are. However it does store codes and they can be flashed out or read with a scan tool for that vintage car...

93 is old enough to read the codes with a paperclip and look it up on the internet, no need to pay for a scantool.

Need a bit more info before any "ideas". Trouble codes can be retrieved by using a paperclip to connect the two top right pins in the ALDL connector under the dash. Just bend the clip out into a straight piece of wire, then bend it into a U shape and put the ends into the two connectors at A and B. Now turn the key ON (DON'T try to start the engine, just ON)

for apicture of the connector and the two terminals to connect Now count the flashes of the SEL.

It will read out the codes in sets of three. So Flash pause Flash,Flash long pause Flash pause Flash,Flash long pause Flash pause Flash,Flash Actually is a code 12 It will flash the code 12 three times to show it is in diagnostic mode, then current trouble codes will flash in order from low to high.

Get those codes and you can look them up online at

Don't jump to the conclusion that the parts referenced are actually bad some items will set codes when it is another part causing the problem. For instance a code 32 says EGR circuit. Could be a bad EGR valve or plugged passages in the intake or head. OR it could just be a piece of carbon sticking the EGR open and causing a very rough idle and hard starting. (VERY common problem with the 4.3)

Follow the diagnostic tree or post back here and someone will be glad to help.

Steve W.