Looking for wiring diagram for Cruise Control System. Fuse good. Left steering wheel switch lights up. In drive, at hwy speed, brake lights not on. Worked fine until 2 months ago. CC will no longer engage. OBDII codes only emission stuff, no codes for Brake/ABS. I'm a Retired USAF Aircraft Electro-Environmental Craftsman, so just need the schematic to troubleshoot further. Any help appreciated.

Do all three of the brake lights work when you press the brake pedal?

Yes. All Brake lights work.

https://charm.li/Buick/2004/LeSabre%...trol%20Module/

FWIW the servos on these have problems.

Pin A: 12 Volts w/CC Sw On. 0 Volt Off..
Pin B: 12 Volts w/Set-Coast Sw depressed, 0 not.
​Pin C: 12 Volts w/Resume-Accel depressed, 0 not.
Pin D: 12 Volts when brake depressed, regardless. of TC on/off. 0 w/TC on/off. 0 if brake off.
Pin E: Ground is good. 0.1 Ohm to frame.
Pin F: 12 Volts Ignition on. 0 off.
Pin G: 12 Volts if Brake pressed, 0 not.
Pin H: 0 Volts just idling. Cant really read this at speed. This is the Inhibit circuit. Also note, this caused a ENG OBD II code as the plug was off the CC Module. It reset after plug put back on.
Pin J: 12 Volt if CC set on, 0 off.
Pin K: 0 Volt at Idle. This is VehicleVehicleSensor. Another can't read while driving. However speedometer/odometer work. Code reader snapshots while driving show VSS is working.

CC module throttle cable good and connected to 'tape ribbon' of the module.

All other OBD II Codes were emissions related, and cleared. Got a Evap leak somewhere 🤪. At this point I'm thinking the CC module is shot...

Thoughts??

Load test the B+ and ground of the module. If good I suspect the module is you problem.

After all electrical checks panned out good, got a module off Ebay from a Oklahoma Salvage Yard. Arrived today, installed in 5 minutes. Took it out for a test drive..working like a champion again.

Schematic of CC System.

Cool!

Thanks for letting us know how it turned out!