2002 Century Engine Brake Quit.

How should I trouble shoot my engine brake quitting? I figure I will check current at the clutch and brake switches first. But I don't know if switches are closed or open when the engine brake is engaged. My next step-if after I determine those switches are working-I will go into the dash and try to make sure the brake switch didn't fail. Has anybody been through this, or familiar with the circuity? Any feedback will probably help. Thanks in advance

 

2002 Century. I forgot to mention checking cruise. Engine brake quit working 3 miles from home. I didn't engage cruise after then-lots of stop lights and traffic. I will try to bump the idle shortly. In the shop now getting ready to troubleshoot.

 

Bumped the idle up to 1000 rpm. So cruise isn't the problem I am guessing.

 

No

 

I was thinking I might just replace that switch regardless. Once in a while the truck acts a little like it going to stall. I'm fairly sure it's not air/losing prime. I've got a FASS and I've replace fuel lines often enough-I think. 2.2 million miles on parts, it might be time to just replace and troubleshoot at the same time.