DTC 63

Wiring Diagram:

CIRCUIT DESCRIPTION
The valve relay provides power to the four ABS valve solenoids and two TCS Pilot Valves in the BPM valve. The valve relay is located on the BPM valve an may be replaced if it is found to be defective.

The valve relay is engaged during normal system operation. When the ignition is switched to RUN, the EBTCM commands the valve relay "ON" by grounding the valve relay actuation line on CKT 879 (EBTCM pin "27"). When this round is provided, the valve relay is energized from the voltage supply line on CKT 854 (EBTCM pin "17"). The valve relay switches and battery voltage is provided to the four valve solenoids, the pilot valves and the valve relay voltage sense line on CKT 851 (EBTCM pin "23"). The valve relay remains engaged until the Ignition is turned "OFF" or a failure is detected.

The valve relay voltage feedback (EBTCM in "32") provides suppression of voltage spikes create during operation of both front AB valve solenoids during antilock and traction control.

TEST CONDITION(S)
1. Tested continuously.

FAILURE CONDITION(S)
1. Less than 5 volts at EBTCM pin "23," valve relay sense;
OR
2. Voltage at EBTCM pin "23," valve relay sense remains high, although voltage at EBTCM pin "27," valve relay control, is low (valve relay sticks).

ACTION TAKEN
1. Code set.
2. ABS/TCS switched "OFF."
3. Red BRAKE warning lamp "ON."
4. ABS and TCS "DISABLED" messages displayed.

When the valve relay is engaged, the valve relay sense line should be at battery voltage. With the valve relay disengaged, the sense line should be at ground. If the commanded position of the valve relay and the position indicated by the sense line do not agree, Code 63 will set. Some conditions which will cause Code 63 to set are:
^ An open circuit on CKT 851 or 879.
^ A short to voltage on CKT 851 or 879.
^ A short to ground on CKT 851 or 879.
^ A defective solenoid valve relay.
^ Open circuit on CKT 854.
^ Loss of voltage to BPM valve terminals "6" and "12" during pump run.

TEST DESCRIPTION
Test numbers refer to circled numbers on the diagnostic chart.
1. Checks for availability of battery voltage to the Valve Relay through Maxi� fuse "1" and CKT 1441.
2. Checks for possible loss of voltage current when system is un er load. At Key-ON, system performs the power on Reset Test and cycles the valve relay, checking the current draw of valves.
3. Checks the Valve Relay coil for proper resistance.
4. Checks for the Valve Relay contacts being internally o en when in the relay unenergized position. Also checks for an 0 en 3 amp fuse internal to vale relay. This fuse maybe "opened" by current surges if the EBTCM does not have a very good ground.
5. Checks for the Valve Relay contacts being stuck open when in the relay-energized position.
5. Checks the integrity of the Valve Relay circuitry internal to the BPM valve.
6. Checks for an open in ground CKT 150.
7. Checks for an open in CKT 851.
8. Checks for an open between splice S105 and EBTCM terminal "23."
9. Checks for a short to ground in CKT 851.
10. Checks for a short to system voltage in CKT 851.
11. Checks for an open in CKT 854.
12. Checks for a short to ground in CKT 854.
13. Checks for a short to system voltage in CKT 854.
14. Checks for an open in CKT 879.
15. Checks for a short to ground in CKT 879.
16. Checks for a short to system voltage in CKT 879.
17. Checks wiring and connectors for intermittents.
18. Determines whether the code was set due to an intermittent condition or an EBTCM fault.
19. Checks if problem found in step 13 is due to a short to system voltage in CKT 874, 879, or 854.

DIAGNOSTIC AIDS
All tests using J 39700 Universal Breakout Box terminal "20" are using the terminal as ground. These tests, of course, assume that the ground CKT 804 at terminal "20" is good.

It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect wiring and connectors may result in misdiagnosis, causing part replacement with reappearance of the fault.