Hello everyone!
I have a couple symptoms and I was wondering if anyone had any idea what is causing it.
My 2003 F-150 XLT 4X4 Extendedcab has been gradually getting worse with these symptoms.

1. Cruise control won't engage or cuts out fairly regularly.
2. Auto Door Locks don't lock the doors immediatly after moving, but sometimes 5-20 minutes into a drive.

I suspect it is a speed sensor. Which one however?

Thanks

 

had similar problems with my truck replaced my GEM due to possible water damage (did this yesterday)

 

GEM doesn't have anything to do with the cruise control on any F150.

Both the speed control and the autolock feature relies on the VSS (Vehicle Speed Sensor) signal. On the 03, this is a "derived" signal rather than one that is directly from a sensor. The OSS on the transmission output shaft is fed into the PCM and the PCM feeds out the result to the various modules as the VSS signal. If you had a sensor problem, it would show up in other operational systems.

I'd be suspicious of an intermittent ground signal from the brake pedal switch circuit, especially if you're experiencing any anomalies with either 4X4 operation or unusual ABS functions.

If you have an overhead console and you're noticing any anomalies with its displayed data, then I'd focus instead on the VSS signal distribution circuit which goes through the CJB.

 

Thanks for this information.

This is the Brake Light Switch you are indicating below correct?

Not the Brake Presure Switch on the Master Cylinder?

 

Yes.

The brake position switch is dual function. One set of contacts is for the stop lamp circuit, the other, separate set of contacts is a signalling circuit for various subsystems that need to know when the pedal is pressed.

 

Replaced the Brake Position switch and it resolved both issues.
Door locked immediatly engage
Cruise control engages immediately and does not disengage.
Thank you for all the help!

 

my cruise control, speedometer and odometer seem to work most the time, failures happen intermediately after a lot of water has entered the cab and a result of rain and windshield leaks. But could the brake position switch be the reason my transfer case motor is not engaging.

 

Most of the time I have heard GEM is the issue here, although the VSS can be the cause of this as well as I believe the VSS will affect all three.

 

swapped gem's, have extra fuse box just in case, kinda interested in what projectSHO89 thinks

 

The GEM has no part in cruise control.
The servo 'controller' is mounted on the servo.
The servo pulls the throttle by cable.
The servo controller is signaled through a mutilead control cable plugged into to the controller, by the steering wheel switches, the brake pedal switch and the brake pressure switch and a speed input signal depending on the year.
To do a diagnostic of the system operate the off switch, turn on the ignition and observe the dash lamp flash telling you you have entered diagnostics.
Operate the on switch and watch for the flash.
Go to the coast, set and resume and look for the flash each time.
If no flash there are failures and flash code may or may not be seen.
The last action will operate the servo and move the throttle.
There are 3 fuses involved.
Again the GEM has no part to play in these actions.
Good luck.

 

I think that since you have a 97 and this thread was about an 03 (the systems are slightly different), you should have started a new thread instead of hijacking this one.

If you have water infiltration into the GEM and CJB, fix the leak and repair any damage.

The 97 doesn't support the self test that BG posted. That's why it's important to properly identify your vehicle in your posting or subject line.

 

yes it's a 97, and i have a related thread with no valid responses. I've seem knowledgeable information from you but I'm unable to PM you directly.

 

I thought there was a switch on the brake pedal arm itself for the tail lamps?

 

That's where the switch I described is located.

 

so if the electronic 4x4 system not controlled by the gem, i know the physical components and the soleniods are good because if i turn the transfercase with pliers it engages and works.