P0504-BRAKE SWITCH A/B CORRELATIONFor a complete wiring diagram Refer to Section 8WWhen Monitored:With the ignition on. VSS indicates increasing and decreasing vehicle speed. APP Sensor indicates increasing and decreasing acceleration demand.Set Condition:The ECM determines that the brakes have been applied without the receiving an input from the Primary Brake Switch Signal and Secondary Brake Switches.
Possible CausesINTERMITTENT CONDITION(Z914) GROUND CIRCUIT OPENSTOP LAMP SWITCH(F941) IGNITION SWITCH START/RUN CIRCUIT(B15) BRAKE SWITCH 1 SIGNAL CIRCUIT SHORTED TO GROUND(B15) BRAKE SWITCH 1 SIGNAL CIRCUIT OPEN(B16) BRAKE SWITCH 2 SIGNAL CIRCUIT SHORTED TO VOLTAGE(B16) BRAKE SWITCH 2 SIGNAL CIRCUIT OPENENGINE CONTROL MODULE
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.(Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)Diagnostic Test1.CHECK THE BRAKE SWITCH 2 STATUSTurn the ignition on.While observing the BRAKE SWITCH 2 status on the scan tool display, press and release the brake pedal several times.Does the scan tool display BRAKE SWITCH 2: PRESSED and NOT PRESSED for the appropriate pedal position?YesGo To2NoGo To112.CHECK THE BRAKE SWITCH 1 STATUSWhile observing the BRAKE SWITCH 1 status on the scan tool display, press and release the brake pedal several times.Does the scan tool display BRAKE SWITCH 1: PRESSED and NOT PRESSED for the appropriate pedal positionYesGo To3NoGo To43.INTERMITTENT CONDITIONWHEN THE ENGINE IS OPERATING, DO NOT STAND IN A DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE PULLEYS, BELTS OR FAN. DO NOT WEAR LOOSE CLOTHING.The conditions that set the DTC are not present at this time. The following list may help in identifying the intermittent condition.With the engine running at normal operating temperature, monitor the scan tool parameters related to the DTC while wiggling the wiring harness. Look for parameter values to change and/or a
DTC to set.Review the DTC When Monitored and Set Conditions. If possible, try to duplicate the conditions under which the DTC was set.Refer to any Technical Service Bulletins (TSB) that may apply.Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or partially broken wires.Visually inspect the related wiring harness connectors. Look for broken, bent, pushed out, or corroded terminals.Were any of the above conditions present?YesRepair as necessary.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoTest Complete.4.(B15) BRAKE SWITCH 1 SIGNAL CIRCUIT VOLTAGETurn the ignition off.Disconnect the Stop Lamp Switch harness connector.Turn the ignition on.Measure the voltage between the (B15) Brake Switch 1 Signal circuit and ground.Is the voltage above 9.0 volts?YesGo To5NoGo To85. STOP LAMP SWITCH - SIGNAL 1 CKT OPENWhile monitoring the BRAKE SWITCH 1 status with the scan tool, connect a jumper wire between (Z914) Ground and the Brake Switch 1 Signal circuit.Does the scan tool display change from PRESSED to NOT PRESSED?YesAdjust or replace the Brake Lamp Switch in accordance with the Service Information.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To66.(Z914) GROUND CIRCUIT OPENTurn the ignition off.Measure the resistance between ground and the (Z914) Ground circuit.Is the resistance below 10.0 ohms?YesGo To7NoRepair the (Z914) Ground circuit for an open.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)7.ENGINE CONTROL MODULE - INTERNALIf there are no possible causes remaining, view repair.RepairReplace and program the Engine Control Module in accordance with the Service Information.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)8.(B15) BRAKE SWITCH 1 SIGNAL CIRCUIT SHORTED TO GROUNDTurn the ignition off.Disconnect the ECM harness connectors.Measure the resistance between ground and the (B15) Brake Switch 1 Signal circuit.Is the resistance above 1000 ohms?YesGo To9NoRepair the (B15) Brake Switch 1 Signal circuit for a short to ground.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)9.(B15) BRAKE SWITCH 1 SIGNAL CIRCUIT OPENMeasure the resistance of the (B15) Brake Switch 1 Signal circuit between the Stop Lamp Switch harness connector and the ECM harness connector.Is the resistance below 10.0 ohms?YesGo To10NoRepair the (B15) Brake Switch 1 Signal circuit for an open.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)10.ENGINE CONTROL MODULE - BRAKE SWITCH 1 SIGNALIf there are no possible causes remaining, view repair.RepairReplace and program the Engine Control Module in accordance with the Service Information.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)11.(F941) IGNITION SWITCH START/RUN CIRCUIT OPENTurn the ignition off.Disconnect the Stop Lamp Switch harness connector.Turn the ignition on.Using a 12-volt test light connected to ground, check the (F941) Ignition Switch Start/Run circuit.Does the test light illuminate brightly?YesGo To12NoRepair the (F941) Ignition Switch Start/Run circuit for an open.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)12.STOP LAMP SWITCH - BRAKE SWITCH 2 SIGNAL OPENWhile monitoring the BRAKE SWITCH 2 status with the scan tool, connect a jumper wire between the Brake Switch 2 Signal circuit and the (F941) Ignition Switch Start/Run circuit.Does the scan tool display change from PRESSED to NOT PRESSED?YesAdjust or replace the Brake Lamp Switch in accordance with the Service Information.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To1313.(B16) BRAKE SWITCH 2 SIGNAL CIRCUIT SHORTED TO VOLTAGETurn the ignition off.Disconnect the ECM harness connectors.Remove the ASD Relay from the TIPM.Connect a jumper wire between cavity 30 and cavity 87 of the ASD Relay connector.Turn the ignition on.Measure the voltage between the (B16) Brake Switch 2 Signal circuit and ground.Is the voltage above 1.0 volt?YesRepair the (B16) Brake Switch 2 Signal circuit for a short to voltage.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To1414.(B16) BRAKE SWITCH 2 SIGNAL CIRCUIT OPENTurn the ignition off.Measure the resistance of the (B16) Brake Switch 2 Signal circuit between the Stop Lamp Switch harness connector and the ECM harness connector.Is the resistance below 10.0 ohms?YesReplace and program the Engine Control Module in accordance with the Service Information.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoRepair the (B16) Brake Switch 2 Signal circuit for an open.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)