Cruise Control Issues

NickM

Member
Ok so I bought an 03 P5 about 2 weeks ago and I love the car it rocks. But there are a few issues I'd like to fix. One of which is the cruise control... Its not working. The guy I bought it from told me it worked but on my way home i plugged my cheap phone charger in and blew a fuse under the dash. Not sure if that had anything to do with the cruise control but this is where it started. Shortly after this happened I attempted to use the cruise control and got nothing. I got home and replaced the blown fuse but still nothing. I checked all fuses and everything checks out. Although when I turn the main power on by pressing the button in, I can hear an audible click coming from under the dash on the passenger side which tells me its prob a relay or the module is engaging or at least trying.... I dont have any lights on the dash and I haven't done too much further inspection of the system. I got the shop manual and read the section about inspection of the system but it uses a few terms im unfamiliar with such as "DTC" and some others. If anyone has some insight or a link to something helpful on this I would greatly appreciate it. Oh and I drive an auto if that helps. Thanks in advance for all your help!
 
FYI, when I turn on the main power for the cruise, I get that same relay noise on the passenger side, and my cruise works. So thats a good sign.

When you say no lights on the dash, are there none there at all, or just none for the cruise control?

Have you checked all of the other fuses in the box?
 
DTC stands for "Diagnostic Trouble Code" or something similar. It's basically the codes that you pull using a scan tool if your check engine light is on.
 
my cruise control is kinda sketchy. about a year and a half ago I was using it on a road trip and it just stopped working. I turned it off then back on and it worked fine. ever since then it works when it wants to. I never got it checked out because I dont use it that often, but I just wanted to let you know that you're not the only one that is having problems with theirs.
 
There's been threads in past about sketchy cruise module action. Mine has to be turned on/set/turned off 3 times on avg before it'll actually take over. Of course I hardly ever use it so isn't really an issue. It's been that way pretty much since car was new. It still always works after that 3 set process so just never have done anything about it. Actually broke down & drove the car instead of the truck last week & used cc early in a.m. on the way to work, same process but once it's engaged it works correctly.
 
New car to you so i will ask...

Are you sure you are engaging properly?

Speed > 30MPH?
Main switch pushed 'in' (no indication)
'Set' pressed and released (now you should get a 'cruise' light)

No foot resting on the brake pedal?
Brake lights functioning properly (on and off?)

Good luck! I hope this was helpful...
 
FYI, when I turn on the main power for the cruise, I get that same relay noise on the passenger side, and my cruise works. So thats a good sign.

Thank you this is useful information.

When you say no lights on the dash, are there none there at all, or just none for the cruise control?

No warning lights at all including no lights for CC, by this I was just saying that there dont seem to be any other issues with the vehicle that may interferre with the CC working properly and I dont get any indication that the CC is trying to work besides the sound from under the dash.

Have you checked all of the other fuses in the box?

I have checked as many fuses as i have found and the only blown one is a 20 amp that killed the power to my DC jack.
 
New car to you so i will ask...

Are you sure you are engaging properly?

Speed > 30MPH?
Main switch pushed 'in' (no indication)
'Set' pressed and released (now you should get a 'cruise' light)

I follow this exact procedure but i still do not get an indicator light for the CC light when i press 'Set' or 'Resume'

No foot resting on the brake pedal?
Brake lights functioning properly (on and off?)

I keep my feet clear, and the brake lights function properly, although i havent inspected the switch down there to see if its adjusted properly.... are there multiple switches on the brake pedal or do the brake lights and CC use the same switch?
 
Thank You all for your help and insight!!!! If anyone else has any info that may help I would greatly appreciate it!
 
Huh.

The brake switch operates the lights and sends a signal to the ECU telling it to cancel CC. So if the brakes are good - the switch is good.

When you initial key on and get all the dash lights - does the CC light come on?

It may be the lightbulb (it may close the circuit to operate)...
 
Huh.

The brake switch operates the lights and sends a signal to the ECU telling it to cancel CC. So if the brakes are good - the switch is good.

When you initial key on and get all the dash lights - does the CC light come on?

It may be the lightbulb (it may close the circuit to operate)...

hmm not sure Ill have to check this.... Im assuming that yours does when you start it?
 
I don't think mine shows when key first on. only when armed with pwr button on steering wheel then set is pushed. green light on top of instrument cluster saying cruise.
 
I don't think mine shows when key first on. only when armed with pwr button on steering wheel then set is pushed. green light on top of instrument cluster saying cruise.

Ok cause I checked mine this weekend and mine definately did not com on when i first turned the ignition on.
 
I'll give it a shot...
When I got my P5 3 years ago, I hated the different heights of the brake/gas pedals. I didn't like the fact that if I slid my right foot to the left from the gas pedal that I would hit the side of the brake pedal. So I got under the steering column and adjusted the brake pedal. I moved the brake pedal further back towards the height of the gas pedal. I lost my cruise control without knowing it right away. My brakes and brake lights worked properly. For some reason (I forget why) I fiddled with the brake switch a few months later. My cruise control came back. I can't recall exactly WHY, but if I remember correctly, the height of the brake pedal is related to the point that the brake lights engage and the cruise control shuts off. My advice is to adjust the brake pedal by bringing it a few degrees upward. I believe you'll need 2 wrenches.... I'll try to look for the page that helped me adjust mine...
 
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