Antilock Braking System (ABS)

DTC 41, 42, 46, 51, 52, 55 & 56 Inlet/Outlet Valve Circuit Open Or Shorted (part 1 Of 2):

DTC 41, 42, 46, 51, 52, 55 & 56 Inlet/Outlet Valve Circuit Open Or Shorted (part 2 Of 2):

Inlet/Outlet Valve Circuit Open Or Shorted:

CIRCUIT OPERATION
Inlet Valves
Voltage is applied to the normally open inlet valves whenever the main relay is energized. An inlet valve closes when the EBCM/EBTCM supplies a ground path at the inlet valve control terminal. The EBCM/EBTCM closes an inlet valve for short periods to maintain (hold) or reduce pressure at a particular wheel.

Outlet Valves
The normally closed outlet valves operate similarly to the inlet valves, except that when the EBCM/EBTCM grounds an outlet valve, the valve opens instead of closes. The EBCM/EBTCM opens an out let valve for short periods to reduce pressure at a particular wheel.

VALVE MODES
Pressure Increase
The pressure increase position is the operating valve position for normal (non-ABS) braking and traction control mode (when equipped). The EBCM/EBTCM does not energize either valve, leaving the inlet valve open and the outlet valve closed.

Pressure Hold
The pressure hold position occurs when the EBCM/EBTCM first notices an impending wheel lockup condition. This signifies and over abundance of hydraulic brake pressure at the locking wheel. The EBCM/EBTCM closes the corresponding inlet valve in an attempt to avoid any additional hydraulic pressure increase at the wheel.

Pressure Reduce
During a wheel lockup condition, the EBCM/EBTCM closes the inlet valve while pulsing open the outlet valve. This decreases hydraulic pressure at a specific wheel without decreasing overall system pressure. The reduced hydraulic pressure allows greater wheel spin, eliminating the wheel lockup condition.

TEST DESCRIPTION
This test checks for proper inlet and outlet valve operation. The wheel brake behavior must be checked to verify the valves hydraulic effectiveness. This is accomplished using a Tech 1 to actuate the valves.

FAILURE CONDITIONS
DTC 41, 42, 45, 46, 51, 52, 55, or 56 sets when the EBCM/EBTCM detects an open or short to ground in the respective inlet or outlet valve circuit.