B663

Code B663:

Cruise Control Circuits:

DESCRIPTION
Code B663 will set and disengage the cruise control if the actual speed is 20 MPH higher or lower than the set speed. This code is used as a type of safety valve to the cruise control system, and can be set under normal conditions if the operator accelerates using the gas pedal and goes 20 MPH over the cruise set speed.

TEST DESCRIPTION
The numbers below refer to circled numbers on the diagnostic chart:
1. Body Control Module (BCM) data value BD7O displays commanded servo position. The commanded range is approximately 4% to 94%. If the servo will not go to full stroke, the vacuum supply, servo, or vacuum brake release circuit is leaking.
2. This step checks to see if the vacuum leak is due to brake release valve and circuit or servo and source vacuum.
3. This step checks to see if vacuum leak is due to vacuum source or servo.
4. This step checks to see if fault is due to intermittent or slow vacuum leak.
5. This step checks to see if fault is servo or brake vacuum release circuit.

NOTE ON INTERMITTENTS
If Code B663 is setting intermittently make sure owner is not "overrunning" the cruise control set speed by more than 20 MPH. Check vacuum source and brake release vacuum lines for proper connections or slow leaks.