Test 26A

Test 26-A, Repairing System Relay Output Circuit:

Test 26-A, Repairing System Relay Output Circuit (Part 3 Of 3):

System Relay Circuits Schematics:

NOTE: You must perform Test 3A, before proceeding with this test.

System Relay Output Circuit

When Its Monitored
The test is conducted after the system relay is turned on and the vehicle speed is above approximately 6 mph. The system relay output voltage is tested once each 5ms.

Set Condition
The system relay supplies the Controller Antilock Brake (CAB) solenoid drivers with B(+) power at cavity 47 when it is commanded on by the CAB. It is turned off by the CAB to shut off Antilock Brake System (ABS) functions in the event of a trouble code or a loss of B(+) to the system. The system relay is supplied B(+) through the relay box from the solenoid fuse (fuse protected). The trouble code is stored if the system relay output voltage at cavity 47 is below 9 volts or above 20 volts for 1 second while in ABS cycling or 20 seconds if not in ABS cycling.

Possible Causes:
^ CAB malfunction trouble code
^ System relay control circuit trouble code
^ 0pen relay box ground circuit
^ 0pen fused B(+) to the system relay
^ Loose or corroded connector terminals
^ System relay output circuit shorted to ground
^ System relay output circuit shorted to B(+)
^ 0pen system relay contacts
^ 0pen system relay output circuit
^ Failed relay box
^ 0pen system relay control circuit