ABS System Self-Diagnostics

SYSTEM INITIALIZATION
System initialization starts when the ignition switch is turned to the run position. At this point the Controller Antilock Brakes CAB performs a complete self check of all electrical components in the ABS and Traction Control systems. Momentarily the build, decay and isolation valves are cycled. If the driyer has their foot on the brake pedal, they may feel the test through brake pedal pulsations. This is a normal condition.

DYNAMIC TEST
Between 5 - 10 mph the pump/motor is momentarily turned on. If any component exhibits a fault during system initialization or dynamic check, the CAB will illuminate the Antilock warning lamp and if equipped with traction control, the Amber Traction Control Warning Lamp. At this time both systems are disabled.

DIAGNOSTIC MODE
To enter diagnostic mode, vehicle must be below 10 MPH. If vehicle speed is not below 10 MPH a no response message is displayed by the DRB scan tool. The following are characteristics of the diagnostic mode. The amber Antilock warning lamp and the red brake warning lamp flash on and off. If a hard fault, such as an Inlet or Outlet Valve fault or Main Relay Power Circuit failure fault is present, the warning lamps illuminate without blinking and no diagnostic operations are available until the fault condition is cleared. ABS and Traction control operation are disabled, during the diagnostic mode. The valves in the valve body cannot be actuated when vehicle speed is above 5 MPH. If valve actuation is attempted above 5 MPH a vehicle in motion message is displayed by the DRB scan tool.

DIAGNOSTIC TROUBLE CODE INFORMATION
Fault codes are kept in a Non-Volatile memory until either erased by the technician using the DRB scan tool or automatically after 50 ignition cycles (key cycles). The only fault that will not be erased after 50 (KEY CYCLES) is the CAB fault. A CAB fault can only be erased by the technician using the DRB scan tool. More than one fault can be stored at a time. The number of key cycles since the most recent fault was stored is also displayed. Most functions of the CAB and ABS or traction control system can be accessed by the technician for testing and diagnostic purposes by using the DRB scan tool. Faults detected by the CAB fall into one of three categories: Locked, Latching, or Non-Latching.

LOCKED FAULT
If a fault is Locked; the ABS and TRACTION CONTROL warning lights will be illuminated and will remain illuminated until the fault code has been erased from the CAB memory using the DRB scan tool.

Locked Faults
^ Valve Power Feed

LATCHED FAULT
If a fault is latched; the ABS and TRACTION CONTROL warning lights will be illuminated and will remain illuminated until the next ignition reset, even if the fault has disappeared.

Latched Faults
^ Pump Motor Circuit Not Working Properly
^ Diagnostic Compare Failure
^ Pump Motor Running Without Command
^ Valve Fault (8/10)
^ Sensor Circuit Failure (4)
^ Signal Missing (4)
^ Wheel Speed Compare (4)
^ Wheel Speed Continuity Above 25 MPH (4)
^ System Under Voltage
^ System Over Voltage

NON-LATCHING FAULT
If the fault is non-latching; the ABS and TRACTION CONTROL warning lights will only be illuminated as long as the fault condition exists. As soon as the fault condition goes away, the warning lights are turned off, although a fault code will be stored by the CAB.

Non-Latching Fault
^ Wheel Speed Continuity Below 25 MPH (4)