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P0504-BRAKE SWITCH SIGNAL CIRCUITS PLAUSIBILITY WITH REDUNDANT For a complete wiring diagram Refer to Section 8W • When Monitored: • Set Condition: Possible Causes INTERMITTENT CONDITION SECONDARY BRAKE SWITCH - SECONDARY SWITCH CKT OPEN (A103) FUSED B+ CIRCUIT OPEN (B16) SECONDARY BRAKE SWITCH SENSE CIRCUIT SHORTED TO GROUND PRIMARY BRAKE SWITCH - PRIMARY SWITCH CKT OPEN (B16) SECONDARY BRAKE SWITCH SENSE CIRCUIT OPEN GROUND CIRCUIT OPEN (L950) PRIMARY BRAKE SWITCH OUTPUT CIRCUIT SHORTED TO VOLTAGE (L950) PRIMARY BRAKE SWITCH OUTPUT CIRCUIT OPEN ENGINE CONTROL MODULE - SECONDARY SWITCH SIGNAL ENGINE CONTROL MODULE - INTERNAL ENGINE CONTROL MODULE - PRIMARY BRAKE SIGNAL Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - Diagnostic Test 1. CHECK THE PRIMARY BRAKE SWITCH STATUS Turn the ignition on. While observing the PRIMARY BRAKE SWITCH status on the scan tool display, press and release the brake pedal Does the scan tool display PRIMARY BRAKE SWITCH: PRESSED and RELEASED for the appropriate Yes >> Go To 2 No >> Go To 11 2. CHECK THE SECONDARY BRAKE SWITCH STATUS While observing the SECONDARY BRAKE SWITCH status on the scan tool display, press and release the brake Does the scan tool display SECONDARY BRAKE SWITCH: PRESSED and RELEASED for the appropri- Yes >> Go To 3 No >> Go To 4 9 - 1448 ENGINE ELECTRICAL DIAGNOSTICS - DIESEL LX |