I've been going through the car fixing little annoying thing, the cable that keeps the glove box from dropping down, the cover for the headlight washer, and a few other things. Now I'm on to the cruise control not working. When I depress the button the red light comes on but when I press the "set" button on the wheel nada. I'm not getting any messages on my dash like "cruise control not working" or any messages related to the brake lights (which all work). From what I'm reading on here these messages show up with that switch on the brake pedal is out or if there's a vacuum issue. Without any messages I have no idea what might be causing it not to work. I don't really want to contort my 77 year old back to get under the dash to take out a perfectly fine switch. Any other way of telling why the cruise control isn't working?

 

If your car is a 2001, the cruise control is fully electronic, only early AJ26 engines were vacuum actuated. With the switch led on, pushing SET+ will mantain the speed you are doing. If not, I think that the first thing to check are the steering wheel buttons.

 

Hey Jaag,

Thank you for the quick reply. Is there any way to test the steering wheel buttons to see if they are the cause of the problem rather than the brake switch?

Joe

 

It's not easy, do the radio controls work? And the horn?

 

​​​​​​​horn is good and the radio buttons work.

 

There are two micro switches in the brake pedal switch, one for the stop lights and one for cruise control. It's possible that the cruise switch has failed. Remove the plug and check the circuits by pushing the pedal while connected to a ohm meter. As I recall, the outer pins are one circuit, inner the other.

 

classic fault for cruise and brake light not working: brake light switch

 

HI RJ & Robak,

Thanks for the info. I've read those threads, just trying to find out if there might be another reason that would be a bit easier to get to.

Joe

 

If only one of the micro switches were faulty, shouldn't the control unit generate an error?

 

With the cruise switch left on when driving you often later get a warning about brake light bulb / ABS issue which is the pointer to your pedal switch being at fault ebay has Aston OEM ones or now China has copied them for a much lesser price. Easy way is to take the switch off new plate and swap that onto the existing plate in the car (many posts on how to do the whole switch replacement job)


I can encourage my cruise to work on occasions or speed up the error on the main panel by fiddling with the cruise buttons. Eg. When driving, press bottom two steering wheel cruise padel buttons just touch (is enough) brake pedal for 1/2 sec now try and set the cruise - it might work. Or same but the. Press the resume button etc. 50/50 I get cruise to work or it encourages fault to appear. (Fault goes away after a lock of doors or stop of engine for 30ish seconds) To pass a mot I just ensure cruise button is off.

So I know I have an intermittent fault (for 5 years) just never got round to buying new switch.

 

Hi Angus,
When you refer to "warning about the brake light bulb" do you mean that one dash warning message or an OBD2 error? I've never had any messages regarding the brake light bulb on my dash screen. I'll try messing with the steering wheel buttons but I'm thinking I'm going to have to get to the brake pedal switch at some point so I might as well just order one and be done with it.
Joe

 

[img alt="Sorry. It is the dash errors. Says Check Rear Lights / Engine Failsafe Mode as per pictures if they appear here.
My example was inaccurate. I meant try when driving and cruise on pressing the Set and RES (hold) and tape the brake pedal. That sometimes resets things and I can hit Set and cruise works. This also brings up the dash errors more quickly. But the errors used to only come up once in a blue moon then they for more frequent. With Cruise off they never come up. Good luck with switch. "]https://cimg9.ibsrv.net/gimg/www.jaguarforums.com-vbulletin/1101x529/img_1130_c17679e3c7999dec8e2c652385f856d5e424441f. jpeg[/img]
Sorry. It is the dash errors. Says Check Rear Lights / Engine Failsafe Mode as per pictures if they appear here. My example was inaccurate. I meant try when driving and cruise on pressing the Set and RES (hold) and tape the brake pedal. That sometimes resets things and I can hit Set and cruise works. This also brings up the dash errors more quickly. But the errors used to only come up once in a blue moon then they for more frequent. With Cruise off they never come up. Good luck with switch.

 

Hey Angus,

No worries. I'm just ordered one of the brake switches anyway. I'll give the wheel switches a try later this afternoon but thus far I haven't been able to get it to work. It's too bad Jag didn't put a Little green light on the dash somewhere to tell you that the cruise control is actually on. The red light on the switch simply means that the switch is depressed. Oh well.

Joe

 

If the light on the switch is on, the computer thinks cruise control is on. The colour or location of that light isn't important - if it's on, then cruise is on.

Yes, you would think if those buttons work, then the cruise buttons will also work, but in fact the cruise buttons have separate wiring. (Cruise goes straight to the ECM, radio controls straight to the radio). Given the lack of any warning messages about the brake lights, or cruise, I would be checking those buttons before doing contortions to change the brake switches.

 

I've already ordered the brake pedal switch but I'll see if I can find the steering wheel button set. I'm thinking I have to pull the part of the steering wheel cover that is between the wheel and the dash to then get to the screws that hold the air bag unit on. Do you happen to know if the pig tail coming from those buttons is inside that cover? I might be able to put a continuity tester on the end of the plug to see if anything happens when I press the buttons.

Thanks for the info,
Joe

 

Just found the steering wheel buttons. Looks like both sets of buttons, cruise and radio, go into one pigtail. Guess I'll be taking the steering wheel apart.

 

You are better off testing the wiring the car side of the cassette, not the wheel side. I assume you'll have to take the knee bolster off to find the connections. Someone else will know.

 

Now it looks like Jaguar change the steering wheel connectors for the Cruise Control and Radio at some point. One type has the wiring for both units meet up at a single pigtail but it looks like at some point they changed the units so that individual plugs inside the steering wheel plug into each unit. Anyone know what year the change was made?

 

The brake switch came in today. I'm sure someone out there knows the answer to this, at rest (in the position it would be in without the pedal depressed) I get a "0" reading on the outside pair of wires. With the switch in the position it would be in with the pedal depressed I get the "0" reading on the center pair of wires. Does this sound like a working switch?

 

Yes, that's what I indicated in post #6.