Any Suggestions please?



Only one thing on our vintage dependable 96 Buick Century 130k that is not working, the cruise control.



It wasn't working when I bought the car about 4 years ago. Then it started working about 1 year ago for a little while.

Now it doesn't work again whatsoever. I've tried to figure out the problem a number of times.

-

The dash "cruise" light will Not come on, even though I'm driving over 35mph and switched to on position on the stock and pressed the set button.



I have the OEM service manual with schematic and connector pin terminals identification and have gone through the 2 page troubleshooting flow chart for non-operative(I'll attach pics).



I followed several times the flow chart trouble shooting tests including turning on the Buick dash "Cruise" light.

It passed till the last thing says, at the bottom of page 8A-34-6, "Check Circuit 389 for poor connection or open between cruise control module conn and Splice 213. If ok, replace cruise control module".



Circuit 389 is terminal E pin in the cruise control module connector and goes to a large connector (C100) at the driver'* side firewall pass through, then to a splice 213 inside the dash within 10 inches of the radio(is what the manual says), then at the splice, it goes both to the vehicle speed sensor and to the PCM, no other breaks.



I did remove terminal E female from the cruise control plug and inspected it has no corrosion and it holds a needle firmly in its female hole.



I did disconnect 36 pins connection 100 and inspected it for corrosion etc and cleaned it well with brake cleaner(the oem lube had turned black and very gooey and lightly sanded male pins with extra fine sand paper and then lightly coated with dielectric grease but no change.



-When the Cruise control module'* plug is disconnected, the Anti-lock brakes dash light comes on.

-I temporarily disconnected the vehicle speed sensor connector by reaching under the car through the passenger side tire to where it is on the transaxle. Disconnected, the speedometer does not work.

-I inspected the cruise control'* ribbon as best I could. It is not twisted or broke that I find.

-I plugged in my obd2 scanner and live data shows the correct vehicle speed when driving but only says the cruise control is disengaged.





I did find online seems to say a 94'96 century/cierra cruise control module is the same.



SO I obtained 2 cruise control modules from the salvage yard. Although they had a different number than mine which is #RE25140858J, yet the number on the other 2, online seems to say are the same units.

No change, the cruise control will not work. I returned the salvage yard modules for credit.

In fact I remember now, I also tried a salvage yard cruise control when I first bought the car and took that back too.



I did look a bit for splice 213-drk grn with the radio, cigarette drawer, and dash sound insulation bottom removed.

The manual says it is bundled with s201-gry, s203blk, s204-pink, s210-blk/wht/blk.

The largest bundle of wires I saw did have all the colors and more and is heavily electric taped.

I don't know if I'll be able to find the splice easily. I'm not sure I've seen a oem splice some to think of it.

I don't know that I will find a problem there. The car doesn't have any sign that of water/rust damage that could cause corrosion in the splice.



=



PERHAPS the trouble shooting flow chart is poorly designed/missing something..



Perhaps I need to find a cruise control module with the exact same part number.



I'm stumped on this. Hmmm



Thank you for any suggestions.



Jim

I didn't read all you did. Did you check the fuse? Switches? Power and ground to the module?

Yes, the 2 page service manual'* trouble shooting flow chart has you do all that with a test light.

A lot of GM in that era checked for the brake light signal before the cruise control would work. It started after the [press brake to shift out of Park] deal started up. Some check off of the brake switch and others check the center high mount brake light.

This one seems to use both the brake light switch and an upper switch just above the brake switch, just for the cruise.
The test checks those and I also unplugged them and checked with a ohm meter.

I wonder if I need a salvage yard cruise module with the exact same part number. I'll look for one when I go again. The 96 and older Centuries are becoming more rare though.

If thew switches are closed and you have good power and ground to the module and the cruise switch is good to turn it on the cruise light should illuminate. If it don't either the light is blown or the module is bad.
These flow charts were better known as TROUBLE trees because they many times led you into trouble.

This supercedes the service data you have IF it has any disagreements, its a TSB from gm
PDF attached

Thank you, this will give me more directions to investigate.

Such as my OEM service manual doesn't tell me that the gear selector could be out of adjustment causing the PCM to impede the cruise(if it thinks it'* in neutral when in drive), like yours shows.

Though, the car needs to go back to my friend'* son to drive so I might not get to check this out more for a year...

Here'* a diagram of the system.
It'* all right here. The switches MUST all be working. Also the light in the cluster MUST be good.

Thank you