I have the same problem that Jason K. has. I have had the throttle body cleaned, the air filter changed, the spark plugs and wires changed, the 8 fuel injectors replaced, the fuel injector wiring harness/connectors changed. I have also had something else cleaned but cannot remember the name of it. The diagnostic tool my brother-in-law has still show #7 injector is misfiring. High mileage, over 199,000. Also, now the braking system light has come on. Brother-in-law trying to figure out what is wrong. We both checked the fluid and it is full. He checked some other things and said he couldn’t find any problem. He said he would research and get back with me. He is still researching. Any guidance would be appreciated.
Swap the coil that fires number 7 cylinder with another coil. If the misfire moves to the cylinder that you swapped coils with, you have a bad coil. Would be what I would try first for the misfire.
I’m not sure on the brakes. If the brake system isn’t losing fluid, make sure the emergency brake pedal isn’t engaged slightly. Also you might make sure the switch on the emergency brake pedal that activates the light on the dash is functioning. I assume there is a fluid level sensor on the master cylinder that triggers the brake light on the dash also. Could be a problem with it assuming the fluid level is ok.
Brake system: This era Chevy’s/GMC trucks are notorious for the ABS / Brake system light being on.
There are a few things to check:
There is a ground connection under the truck on the frame right just about under the drivers seat. Climb under there, and you should see it. Take it off, clean the frame and wire, and reattach.
Then, there is another ground underneath the battery tray. Remove the battery, remove the battery tray, and clean that metal and ground wire and reattach.
This may fix it, but what it more likely is that the ABS module is failing. again, common for this vintage of truck. a code reader that can read ABS codes can get you the codes specifically for this system and help point you in the right direction- but the above grounds are a great place to start.