94 Bonneville cruise control

brianfrank · #1 07-03-2008, 08:18 PM

My cruise control works intermittenly. I have checked all my electrical and vacumn conections. I replaced the actuater with a used one from a wrecking yard ...no difference. the repair manual said to chech the vehicle speed sensor but mine is a sealed unit so I see no way to check it. I did not take off the brake pedal swith off because it is so hard to get to...but the eletrical connection felt good and also the vacume hose.
So i was wondering if there is a better way to diagnosis it besides just replacing parts . Is there one certain part that ussually goes bad? I plan on going on a trip next tuesday and was hoping to be able to fix it before I go. thanks ahead of time for any help Brian

HotZ28 · #2 07-04-2008, 08:47 AM

Is the speedometer working smooth and without fluctuation? If so, the VSS is not the problem! The VSS sends the speed signal to the PCM for pulse interpolation and the PCM in turn uses that information to control the cruise and speedometer output. Usually, cruise problems on the 94-95 are associated with the PCM. The PCM’s on the 94-95 models are known to be somewhat flakey. Have you checked the switch on the steering column?

brianfrank · #3 07-05-2008, 12:15 PM

My speedometer is working fine so I agree that the vss is not the problem. as for the PCM I am a little confused....the repair manual that I have said that only 96 and above have a PCM. I also can't locate one on my 94. did you mean the ECM ?
I have not checked the switch on the steering column.....how would I do that? just replace it? thanks for your help!!! Brian

HotZ28 · #4 07-05-2008, 01:07 PM

ECM was the term used for (Engine Control Module), which essentially controlled nothing more than engine functions. When the PCM (Power-train Control Module) started controlling the transmission, the ECM began it’s shift to a PCM. As early as 1992, some cars were equipped with electronic controlled transmissions and they were controlled by the ECM/PCM. 1996 was the first year that all carmakers were required to be fully OBD11 compliant. Some started the transformation early and took a few years to complete. These cars, (including your 94) used an OBD1 ECM with the OBD11 terminal, consequently, the PCM was commonly referred to as OBD1.5. These were used in many 94-95 models, until the full mandatory conversion to OBD11 in 1996. Your ECM/PCM is located under the passenger side dash. If you want to replace the multi-function switch, remove the little cover below the switch and unplug the connector. The switch lever will pull straight out (with a little persuasion)!

Jrs3800 · #5 07-05-2008, 01:47 PM

Check and make sure the Vac line to the Servo is good... If this line gets sucked flat you will have a Cruise Control Vent Solenoid Error Code... And the end result with this vac line is usually that the cruise will work for a while until the line collapses...

brianfrank · #6 07-06-2008, 12:46 AM

thanks for the lesson on ECM/PCM. I also took off my multi-function switch just to check the connection....I had no idea it was that easy to remove. I will replace it monday when the dealership opens. since it is so easy to change I thought I would try it first.
I will also double check the vacumn lines. thanks again and I will let you know how things turn out. brian

brianfrank · #7 07-07-2008, 11:05 PM

So today I went to the wrecking yard and bought another multi-function switch. Still no cruise control. It's not working at all the last couple of days. So then I went to the pontiac dealer and asked them about the EMC...they said it wouldn't effect the CC in my car. So now I was contiplating what parts to buy new and see if it helps. they had none of the parts in stock and I am leaving tommorow so I decided to wait. When I got home I took my acculater completly apart and cleaned it up , put it back together and tryed that. The cruise worked good. Tried it several times and worked great. Problem solved GREAT!! only one problem I just ran to the store and it didn't work...bummer. But I do believe it is the acculator though...when I get back from my trip I will buy a new one. Thanks again for all the help..... I learned a few things. I am new to the form thing but I think I am to mark this closed...so I will try but if i don't get it I may need more help. Brian

Jrs3800 · #8 07-08-2008, 12:47 PM

You honestly need to get a scan tool on the car to see what actuation you are getting from the stalk.. When the cruise id dead, you need to know if the PCM is seeing the request for cruise... The PCM is part of the loop but iirc the CC system has its own module( They rarely fail )

POST REPLY TO THIS THREAD