DTC 48

Fig. 141 Code 48: Left Front TCS Pilot Valve Fault (Part 1 Of 2).:

Fig. 141 Code 48: Left Front TCS Pilot Valve Fault (Part 2 Of 2).:

DTC 48: Left Front TCS Pilot Valve Fault:

CIRCUIT DESCRIPTION
The left front TCS pilot valve in the BPM Valve may be commanded to close, isolating the master cylinder.

The pilot valve circuits receive power through the valve relay on the BPM Valve. The valve relay is engaged at KEY-ON and remains engaged throughout the ignition cycle. Pilot valve 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 pilot valves.

TEST CONDITION(S)
1. Tested continuously.

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

ACTION TAKEN:
1. Code set.
2. ABS/TCS switched "OFF."
3. "ANTILOCK" indicator "ON."
4. "TRACTION DISABLED" message displayed.

Code 48 will set when the expected position of the right front TCS pilot valve does not match the commanded position from the EBTCM. Conditions which could cause Code 48 to set are: damage to the right front TCS pilot valve; an open circuit; or a short circuit to ground or battery on CKT 1657.

TEST DESCRIPTION
Test numbers refer to circled numbers on the diagnostic chart.
1. Damage to CKT 886 may result in multiple valve solenoid codes setting.
2. Checks CKT 886 for opens or high resistance from EBTCM/EBCM terminal "23" to "32".
3. Determines which branch of CKT 886 has an open or high resistance.
4. Checks the integrity of CKTs 1657 and 886, the TCS Pilot Valve circuitry internal to the BPM Valve, and the TCS Pilot Valve Solenoid coil.
5. Determines whether a problem found in Step 4 is due to an open in CKTs 886, 1657 or a faulty BPM Modulator Valve.
6. Determines whether the problem found in Step 4 is due to an open in CKT 886 or 1657.
7. Checks for a short to battery in CKT 886 using EBTCM/EBCM terminal "20" as ground.
8. Checks for a short to battery in CKT 1657, using EBTCM terminal "20" as ground.
9. Checks for a short to ground in CKT 886 using EBTCM terminal "20" as ground.
10. Checks for a short to ground in CKT 1657, using EBTCM terminal "20" as ground.
11. Checks for connector or wiring problems which could cause intermittents.
12. Uses the TECH 1 to exercise the TCS pilot 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 ground. These tests, of course, assume that the ground CKT 1250 terminal "20" is good.

If Codes 44 and 48 are both set, the fault is likely to be an open or short in CKT 886.