Speed Control Diagnostic Tips
Servo Pin-Out Test TipsNOTE
MEASURING THE RESISTANCE OF A SERVO WILL INDICATE THAT A SERVO IS BAD IF READINGS ARE OUTSIDE THE RANGES SPECIFIED BELOW. HOWEVER, A SERVO CAN HAVE RESISTANCE READINGS WITHIN THE SPECIFIED RANGES AND STILL BE FAULTY.
The following readings are the expected values for a good servo.
Resistance between Pins: 1 and 2, 1 and 3, and 1 and 4 should measure between 1 and 5 ohms and should be similar in value between pin sets. These are the three phases of the motor. Resistance between Pins 5 and 6, should measure between 20 and 30 ohms. This is the winding of the clutch. These readings should not change with polarity.
DST Testing Tips (TPS PID)
Pinpoint Test: The Speed Control Does Not Disengage When The Brakes Are Applied
With the vehicle speed above 30 MPH (48 Km/h) engage the speed control. Then check to see if the TPS PID returns to base voltage when the brakes are applied. If it does return to base voltage, then the speed control system is working. Need to advise customer that tapping the brakes deactivates speed control and that the brakes must be applied to make the vehicle slow down.
NOTE
CHECK FOR CALIBRATION SERVICE MESSAGES RELATING TO DASHPOT OR IDLE SPEED CONTROL UPDATES.
Deactivator Switch Inspection Tips
A faulty deactivator switch can result in intermittent or inoperative speed control. There are two types of deactivator switches; a brake line pressure switch, which is integrated into the brake master cylinder, and a pedal travel switch, which is connected to the brake pedal arm.
Proper switch function should be confirmed. Inoperative switches of both types should be inspected for connector corrosion or pin push-out. Pedal travel switches should also be inspected for proper mechanical adjustment relative to brake pedal travel.
Intermittent Speed Control Operation Tips
Intermittent or irregular speed control operation may be traced to poor pin contact between the PCM pins and the mating wiring harness connector terminals. Indication of this condition is that the speed control indicator lamp on the instrument panel will illuminate but the servo will not actuate the throttle. This can be tested by using a test lamp at the servo connector while running the self test. Pins 2, 3, and 4 to B+ the lamp should flicker slightly at the end of the test for 4 seconds. This indicates the phases of the motor firing in sequence. Pin 5 top B+ the lamp should glow solid at the end of the test for 4 seconds. This represents the speed control clutch circuit operation. Pins 1, and 6 to ground should glow brightly when the ignition is on.