Diagnostic Aids

Code 63 indicates that the Cruise Control was engaged at a certain set speed and the vehicle speed was more than 20 miles per hour above or below this set speed. Whenever the condition which set Code 63 is present, the Cruise Control will disengage.

1. Code 63 may result from operator error or a system malfunction. To diagnose a system malfunction, proceed as follows:
   • A. The engine must be running.
   • B. Turn the engine off and within 2 seconds, turn the ignition on.
   • C. Turn the Cruise Instrument Panel switch to the on position.
   • D. Enter diagnostics and the output cycling tests series 9.6.
   • E. Check the cruise control vacuum and power solenoids to determine if they cycle (click) on and off. If the vacuum and power valves are OK, check for binding linkage. If the linkage is not binding, check for vacuum leaks or blockages. If there are no vacuum problems, then the DFI system is OK.
2. If the vacuum valve does not cycle, disconnect the vacuum valve connector and connect a test light between the harness connector pins while performing the output cycling tests. If there is no light, check circuit 919 or 403 for an open. If the wiring is OK, check for a shorted cruise control vacuum valve. This valve may contain a diode. The properties of a diode are such that current will pass through it in one direction only. Since the polarity of the meter may influence readings when measuring the resistance across the valve (harness disconnected), first measure the resistance in one direction and then reverse the leads of the meter to measure the resistance in the other direction. If both readings are less than 20 ohms, the diode or solenoid is shorted within the valve causing damage to the ECM. Replace both the ECM and the cruise control vacuum valve. If either reading is greater than 20 ohms, the valve is operating normally. Check for a faulty ECM connector or a faulty ECM. If there is a steady light, check circuit 403 for a short to ground. If the circuit is OK, check for a faulty ECM connector or faulty ECM.
3. 3) If the light is on for 3 seconds and off for 3 seconds then the ECM and wiring harness are OK, replace the vacuum valve solenoid. If the power valve does not cycle, disconnect the power valve connector and connect a test light between the harness connector pins while performing the output cycling tests. If there is no light, check circuit 402 for a short to ground. If circuit 402 is shorted damage may have resulted to the ECM. Repair short and check for a damaged ECM beginning at step 1). If circuits 402 and 153 are OK, check for a shorted cruise power valve. This valve may contain a diode. The properties of a diode are such that current will pass through it in one direction only. Since the polarity of the meter may influence readings when measuring the resistance across the valve, (harness disconnected), first measure the resistance in one direction and then reverse the leads of the meter to measure the resistance in the other direction. If both readings are less than 20 ohms, the diode or solenoid is shorted within the valve causing damage to the ECM. Replace both the ECM and the cruise power valve. If either reading is greater than 20 ohms, the valve is operating normally. Check for a faulty ECM connector or a faulty ECM. If there is a steady light, check circuit 402 for a short to voltage. If circuit 402 is OK, check for a faulty ECM connector or faulty ECM. If the light flashes continuously, the ECM and the harness are working properly, replace the power valve solenoid.