Originally Posted by Jeffrey
Mine died just thus past week. Is it an epidemic? My scan gage shows no codes. ?
I guess I need to be clearer when I say brake light switch.
It could be either the brake light switch, the one that turns the brake lights on or more likely the brake pressure switch on the master cylinder. The brake pressure/cruise deactivation switch is the part that has been recalled and superseded a few times for the 2003 and older Fords but they are prone to failure on all Fords, especially if the brake fluid is dirty. This is the part that deserteagle56 had replaced to fix his, they are only $20 to buy plus brake fluid and labor if needed. It is one thing that might not show a code unless it is shorted (the older Ford Cruise Control fires are caused by this switch). The brake light switch goes closed when you press the pedal. The Brake Pressure switch goes open when the pressure goes up when the brakes are applied. It is hydraulic and works with brake fluid pressure. (has the brake fluid been correctly serviced every 2-3 years?) That might not show a code because it is normal but does not work when it should, it just thinks you never pressed the brakes so its normal. What could be happening is as the fluid gets hot it no longer opens when the brakes are pushed. If the fluid is dirty it could be blocked because (at least on my van) it is located on the bottom of the master cylinder. Also your scan tool might not be able to see all of the codes either as scan tools only have to be able to read the basic codes not all of the codes that Ford can see with their tool. Depending on your scanner you might be able to see if the brake light switch opens and closes within the PCM (Powertrain Control Module) and that the brake pressure switch is working.
Someone said something about the Wrench Light being on. The Wrench Light is for the Electronic Throttle Control subsystem. (ETC) or as some call it fly by wire. If the Wrench Light comes on the system has a fault and the cruise control will not work. Many newer cars and trucks (most?) do not have throttle cables any more and the throttle is opened and closed by the PCM (in Fords case) This is also how the cruise control is controlled as well as any idle adjustments are made.(park or drive, A/C compressor on or off, cold or hot engine, things like that)
So on these newer vans the engine control modual runs the cruise they are no longer a separate cruise control unit. Here is a list of inputs that it needs to see for the cruise to work from the 2008 Ford work shop manual.
Brake/Stop light switch
Transmission output shaft speed sensor (OSS)
Digital transmission range sensor (TR)
Speed/Cruise control switches
Speed/Cruise control deactivator/brake pressure switch
Accelerator pedal position sensors
Parking brake off
There is a lot of information in the manual like this basic information part,some of these I didn't know about.
Any faults in the PCM or ETC systems the cruise will not work (safety reasons)
The Transmission selector has to be in Drive or Overdrive or the Cruise will not work
If the set speed is over ridden by the throttle/accelerator pedal for more than five minutes the cruise will shut off.
If the van speed loss is more than 10 MPH when the cruise is on it will shut off.
If it drops below 30 MPH it will shut off
If the steering wheel switch is pressed or stuck for longer than two minutes it will shut off.
If the parking brake light come on, it will stop working.
So things to check for.
Do you see the green cruise on light when the cruise switch is pressed while over 25 or so mph?
With the key on (not started) do you see the brake warning light come on without the emergency brake set? It should come on for a few seconds and them go off as a self test. If not that is the brake pressure switch going bad. Try is as soon as the cruise stops working in case temperature matters.
Are the steering wheel switches free moving and not sticky or anything.You and push them all you want when the van is off.
Does your steering wheel make any noises when turning, clock spring could be going bad.
Are there any warning lights on (brake, wrench, or check engine) when the cruise does not work?
Is it going in to drive correctly? Is the shift lever moving OK?
Does the speedometer work OK?
Is the parking brake light off? Does it stay off while driving?
If all that is good I would replace that brake pressure/cruise deactivation switch, clean and flush the brake system, fill with the proper brake fluid and I bet the cruise will work just fine. Unless you have a Check Engine or Wrench Light and that should be a code you can pull up to find what wrong.