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Discussion Starter #1
Hey,
Posting this for my wife's car. She drives a 2005 Impala with the 3.4. Just out of the blue her cruise stopped working and has not worked since. Brought the car to the dealer to get diagnosed. They told me it's the cruise control module. I went to the salvage yard and picked one up. Didn't work. So I tried two others and they didn't work. Brought the car back to the dealer and they still say it's the module. Got another salvage yard unit from another place that has better reputation. It still doesn't work. NO "cruise" light in the dash. Nothing. System is dead. Any suggestions? I was thinking it may be the set switch in the steering wheel. I also thought about taking the unit out of my 03 alero and swapping it in to see if that works because the module is the same. The brake lights all work. Nothing loose on either brake switch. Planning an out of state trip later this month and would really love to have cruise. I'm a second year tech student so I understand most technical information if anyone wants to post that.

Thanks
 

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Discussion Starter #2
Anyone? Also I checked both fuses and they are good. Gonna try swapping the module out of my Alero in it tonight and see what happens
 

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Hey Blupala, welcome to the forum. Unfortunately I don't have an answer for you.
I do remember hearing that a vacuum leak can lead to cruise control not working, but I don't remember under what circumstances. I don't think it's applicable because you're saying your light wont even go on.

I didn't want you to think that no one saw your post, we all did (probably) but since it's not a common problem no one has posted an answer.
 

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Discussion Starter #4
Thanks for the reply. I don't think it's vacuum as the cruise is electronically controlled
 

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OK, do you have any issues with the brake pedal or brake pedal switch? Are you brake lights on even when your foot isn't on the pedal?
 

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Mr. Handy
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Also check parking brake. If ur parking brake light is on on the dash I believe the cruise control will not work.
 

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Discussion Starter #7
OK, do you have any issues with the brake pedal or brake pedal switch? Are you brake lights on even when your foot isn't on the pedal?
Does not seem to be any issues with either brake switch. All the lights work when pedal is depressed. They shut off when you let off the pedal. Connectors are tight and both switches are firmly mounted.
 

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Discussion Starter #12
Found this on another website. gonna test the car out in the next day or two.

I have a 2004 Impala, so I'll assume the wiring diagrams are similar. On my diagrams, there are two white wires going to the module which is located at pins "G" and "J". There should be no voltage at pin "G" until the brake switch is applied. This switch is also used to operate the brake lights. The two wire colors on this switch are white and orange. At pin "J", this signal goes to the PCM to tell it that the cruise control module is engaged. The info on the cruise control connector is shown below:

Pin A: gray - cruise control on switch signal: 12VDC with cruise switch on
Pin B: dark blue - cruise control set/coast switch signal: 12VDC with switch pressed
Pin C: gray/black - cruise control resume/accel switch signal: 12VDC with switch pressed
Pin D: brown - cruise control release signal: 12VDC with brake pedal not pressed: 0V when pressed
Pin E: black/white - ground
Pin F: brown - ignition 3 voltage: 12VDC with ignition on
Pin G: white - stop lamp switch signal: 0V with brake pedal not pressed: 12VDC when pressed
Pin H: dark green - cruise control inhibit signal: 0V if PCM detects an inhibit condition
Pin J: white - cruise control engaged signal: voltage (unsure of value, either 12VDC or 5VDC) when signal engaged
Pin K: dark green - vehicle speed signal: 1 to 5 volts depending on speed


This view of connector is facing it after it is separated.

After posting the connector view, the lines don't quite line up, but at least it should show you the pin positions.
________________________
| | |
| F | G H J K |
| | |
| E | D C B A |
|__|___________________|
 

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Discussion Starter #14
Well found out today every input into the box is working properly. Only thing that concerns me is the wire for the cruise control inhibit from the pcm had 0v which means the pcm had shut down the cruise. This could be due to the fact that the car wasn't moving or there is another problem with the car causing the cruise to be shut down. I tried another box and it didnt work. I know the box works because I tried it in my Alero and it worked perfectly. So for some reason in the Impala the pcm is shutting the cruise down. here is what I found on this situation.

Cruise Control Inhibited
The powertrain control module (PCM) inhibits the cruise control operation when any of the following conditions exist:

* A cruise control related DTC has been set.
* The vehicle speed is less than 40.2 km/h (25 mph) .
* The vehicle is in PARK, REVERSE, NEUTRAL, or 1st gear.
* The engine RPM is too low.
* The engine RPM is too high, with fuel cut off.
* The vehicle speed is too high, with fuel cut off.
* The system voltage is not between 9 volts and 16 volts .
* The Traction Control System (TCS) is active for more than 2 seconds .
 

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Found this info searching around, maybe it will help you out.

GM troubleshooting diagram-
http://ww2.justanswer.com/uploads/molurch/2010-08-18_134116_cruise.pdf

Below are some common causes of cruise not working- Stolen from a mechanic.

Make sure that-
Brakes not applied.
Brake fluid full.
Parking brake off.
Engine temperature at least 140'
Transmission in Drive.
Cruise control switch on.
 

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Discussion Starter #17
Thanks. I got that flow chart everything checks out according to the chart. All the other stuff you listed is true. Engine was warm and no brakes applied. Was doing 60mph.
 

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Discussion Starter #19
Ran out of money so can't take car to shop. I just don't understand whys it won't work when all the inputs work. All I can think is the PCM is sending an inhibit signal to it by opening the ground
 

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No idea. Can you test the switch and button on the steering wheel for continuity?
If everything else checks out it may be something stupid. Also, where are you located?
 
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