Antilock Braking System (ABS)

Wiring Diagram:

CIRCUIT DESCRIPTION
The right rear valve solenoid in the BPM Modulator Valve may be commanded to three different positions by the EBTCM. Valve position is determined by the amount of current which is allowed to flow through the valve solenoid coil.

The valve solenoid circuits receive power through the valve relay on the BPM Modulator Valve. The valve relay is engaged at KEY-ON and remains engaged throughout the ignition cycle. Valve solenoid circuits should have battery voltage available at all times.

When the key is turned to RUN, power is supplied to the EBTCM. The EBTCM will complete an internal self-check before providing ground to the valve relay. When the valve relay is energized, battery power is supplied to the valve solenoids.

TEST CONDITION(S)
1. Tested continuously.

FAILURE CONDITION(S)
While standing or driving:
1. Valve solenoid cannot be activated.
OR
2. Valve solenoid is activated in a defective way.

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

Code 51 will set when the expected position of the right rear valve solenoid does not match the commanded position from the EBTCM. Conditions which could cause Code 51 to set are: damage to the right rear valve solenoid; and open circuit; or a short circuit to ground or battery on CKT 829.

TEST DESCRIPTION
Test numbers refer to circled numbers on the diagnostic chart.
1. Damage to CKT 851 may result in multiple valve solenoid codes setting.
2. Checks CKT 851 for opens or high resistance from EBTCM terminal "23" to "32."
3. Determines which branch of CKT 851 has an open or high resistance.
4. Checks the integrity of CKTs 829 and 851, the RR ABS Valve Solenoid circuitry internal to the BPM Modulator Valve, and the RR ABS Valve Solenoid coil.
5. Determines whether a problem found in Step 4 is due to an open in CKT 829, 851, or a faulty BPM Modulator Valve.
6. Determines whether the problem found in Step 4 is due to an open in CKT 829 or 851.
7. Checks for a short to battery in CKT 851 using EBTCM terminal "20" as ground.
8. Checks for a short to battery in CKT 829, using EBTCM terminal "20" as ground.
9. Checks for a short to ground in CKT 851 using EBTCM terminal "20" as ground.
10. Checks for a short to ground in CKT 829, using EBTCM terminal "20" as ground.
11. Checks wiring and connectors for intermittents.
12. Uses the TECH 1 to exercise the RR ABS valve solenoid and check it for proper operation.
13. Determines whether the code was set by an intermittent conditions or an EBTCM fault.

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