1994 TD Cruise Control Issue

[dsnyder]

Hello All-

I've just replaced the Turn Signal/Multifunction Cruise Control Switch. My Cruise Control did not work. That is the reason I replaced the switch.

My cruise control now works... intermitantly. It always works the first time engaged but if I have to disengage it, most of the time it will not re-engage. I can hit resume, set, turn it off and on again... makes not difference. Once I restart the engine, it will work again but usually only one time.

The vehicle is a 1994 K2500 Suburban TD. This model has the electronic throttle so there are no cables. All cruise control regular functions are controlled through the ECM. It is almost stock... Heath chip and Heath Turbo Regulator.... Vacuum Pump has been removed.

There is no check engine light on but I have not checked for codes using the jumper switch plug. I plan to do that this weekend but thought someone might have some ideas before.

[racer55]

A failing PMD can affect cruise control.

[HeavyChevy95]

Might try and lift the brake pedal next time.
IF the brakes are worn, it can allowing the pedal to drop just enough to disengage the CC..


OT- How long am I going to have to do this image verification thing?

[john8662]

check the codes, lots of codes, even those that don't turn off the light cause the cruise to no longer function. There is a code for brake switch too.

[dsnyder]

I checked the codes and here are the two I found-

Code 41 -Brake Switch Circuit Fault
Code 49-“Service Throttle Soon” Lamp Circuit Fault

I am guessing the code 41 is the one that is relevant to my cruise not working.

I do have brake lights that light when I step on the pedal. I can change out the switch just for good measure but I'm not really understanding why the fault.

When the cruise control engages, stepping on the brakes does disengage the cruise control. Also, when on coast when stepping the the brake the engine rpm goes down so I'm guessing the ECM is reading the signal from the switch.

Any ideas?

[dsnyder]

OK- I replaced the brake light switch and cleared the code. We'll see if the code comes back and the Cruise Control stops working.

Now here is what has me nervous... That switch and the pushrod that operates the brakes seems to be held on with on silly little clip. If that clip comes off and the pushrod slips out while I'm driving I could immediately and without warning end up with no brakes.

Is there any kind of a safety strap... even like a zip tie the could act as a secondary safety to hold the pushrod on the brake pedal?

Dave