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Intermittent Cruise Control

New 11/19/2004


Hi! I've "lurked" for a while and I have searched all that I can find elsewhere before this, my first post. My red '99 (welded - FPS) was t-boned by a red-light runner and totaled last month at 78k. I have just replaced it with a black '99 with 49k (does anybody recognize a black '99 Texas car, last 4 on the VIN is 1773, as a cam weld before I pull the covers?). The dead one and the black one both exhibit the same problem:

After switching the cruise control ON, pressing SET/ACCEL (at any valid speed) usually results in a brief flash of the CRUISE light and no engagement - though occasionally it will engage and perform faultlessly! Does anyone have a sequence of tests I can use to determine the root cause of the problem? I have checked for standard OBD-II codes and there are none.

BTW, in anticipation of being flamed for audaciously acknowledging that I use cruise control in my SHO, I find it to be the easiest way to avoid speeding tickets after closing my pub in the early hours of the morning - without the cruise control there is just too much temptation to clog on...!

I use the cruise all the time when by myself. Hard to use it with list members.
The system is electronic and has a lengthy IIRC diagnostic tree.
I worked on a 1995 ford Aerostar just before I left the shop floor that had the same problem, that truck was the cruise module down by in the foot well.

Paul can post the Diag by system chart if there is one.

Just a guess, but what if the brake switch was stuck on? Do your
brake lights reliably function normally? I have had the brakes get
stuck on, and had the switch on the brake pedal once that they
wouldn't work at all. That is what disengages the cruise.

Next time it does this, hit resume and see if it does it again (or by
luck it may engage and remain that way)... Reason I say that is
because if the cruise module (electronics) gets turned off resume
won't do anything as the system would need to be turned on and set,
however if the electronics remain "alive" and the brake signal is what
tripped it back off then you would see it try to engage again when you
hit resume.

There is probably a more formal procedure but I am trying to eliminate
the brake switch input to the cruise module. If it does seem to
possibly be the brake switch, the next question is if the
Multi-Function Switch is in the loop with that input to the cruise
control in the GEM or not.

Hope that helps,

Scott "I love my cruise even at 100" Krietemeyer


Inspection and Verification (Start Testing Here)

  1. Verify the customer's concern by operating speed control system to duplicate the condition.
  2. Inspect to determine if one of the following mechanical or electrical concerns apply: VISUAL INSPECTION CHART Mechanical Inspect and verify that:


  1. If inspection reveals obvious concern(s) that can be readily identified, repair as required.
  2. Perform the Self-Test Diagnostics. See: Extracting and Clearing Codes (Self-Test Diagnostics)

Extracting and Clearing Codes (Self-Test Diagnostics)


  1. Enter Self-Test Diagnostics by depressing the speed control OFF switch while turning the ignition key ON, ensuring engine does not start and is not running. The speed control indicator on the instrument panel will flash once to indicate that speed control module entered the diagnostic mode. Five additional flashes at this point indicate a defective speed control servo. Release the OFF switch.
  2. Press the remaining switches in this sequence: ON, RESUME, COAST, and SET/ACCEL. IF THE "ON" SWITCH IS NOT DEPRESSED WITHIN 5 SECONDS AFTER ENTERING THE DIAGNOSTICS MODE, THE MODULE TIMES OUT AND THE PROCEDURE MUST BE STARTED OVER. The speed control indicator lamp will flash as each switch is depressed. Press each switch in the sequence immediately after the indicator light goes out for the previous switch.
  3. A lamp flash with the last button (SET/ACCEL) indicates that the STATIC test passed. If the lamp does not flash with the last button and there are no additional flashes of the lamp, the switch is defective. If the lamp does not flash with the last button, and additional flashes occur, follow the chart below for trouble codes:
  1. Immediately after the static test has passed, the speed control servo will then perform a dynamic test automatically by actuating the throttle lever from 1 mm to 10 mm of travel from the idle position. During the dynamic throttle pull, observe throttle movement to witness any binding or sticking of actuator cable, proper connection of actuator cable to throttle lever, and ensure throttle returns back to idle position. If improper connection and/or binding or sticking of actuator is observed, go to Symptom Chart. See: Symptom Chart
  2. Return ignition switch to the OFF position and proceed to Symptom Chart. See: Symptom Chart




My Thanks to the usual suspect.


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