P0504-BRAKE SWITCH A/B CORRELATION
For a complete wiring diagram Refer to Section 8W
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When Monitored:
With the ignition on. VSS indicates increasing and decreasing vehicle speed. APP Sensor indicates increasing and decreasing acceleration demand.
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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 Causes
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INTERMITTENT CONDITION
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(Z914) GROUND CIRCUIT OPEN
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STOP LAMP SWITCH
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(F941) IGNITION SWITCH START/RUN CIRCUIT
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(B15) BRAKE SWITCH 1 SIGNAL CIRCUIT SHORTED TO GROUND
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(B15) BRAKE SWITCH 1 SIGNAL CIRCUIT OPEN
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(B16) BRAKE SWITCH 2 SIGNAL CIRCUIT SHORTED TO VOLTAGE
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(B16) BRAKE SWITCH 2 SIGNAL CIRCUIT OPEN
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ENGINE CONTROL MODULE
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Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.
(Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)
Diagnostic Test
1.
CHECK THE BRAKE SWITCH 2 STATUS
Turn 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?
Yes
No
2.
CHECK THE BRAKE SWITCH 1 STATUS
While 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 position
Yes
No
3.
INTERMITTENT CONDITION
WARNING:
WHEN 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.
NOTE:
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?
Yes
No
4.
(B15) BRAKE SWITCH 1 SIGNAL CIRCUIT VOLTAGE
Turn 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?
Yes
No
5.
STOP LAMP SWITCH - SIGNAL 1 CKT OPEN
While 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?
Yes
No
6.
(Z914) GROUND CIRCUIT OPEN
Turn the ignition off.
Measure the resistance between ground and the (Z914) Ground circuit.
Is the resistance below 10.0 ohms?
Yes
No
7.
ENGINE CONTROL MODULE - INTERNAL
If there are no possible causes remaining, view repair.
Repair
8.
(B15) BRAKE SWITCH 1 SIGNAL CIRCUIT SHORTED TO GROUND
Turn 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?
Yes
No
9.
(B15) BRAKE SWITCH 1 SIGNAL CIRCUIT OPEN
Measure 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?
Yes
No
10.
ENGINE CONTROL MODULE - BRAKE SWITCH 1 SIGNAL
If there are no possible causes remaining, view repair.
Repair
11.
(F941) IGNITION SWITCH START/RUN CIRCUIT OPEN
Turn 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?
Yes
No
12.
STOP LAMP SWITCH - BRAKE SWITCH 2 SIGNAL OPEN
While 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?
Yes
No
13.
(B16) BRAKE SWITCH 2 SIGNAL CIRCUIT SHORTED TO VOLTAGE
Turn 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?
Yes
No
14.
(B16) BRAKE SWITCH 2 SIGNAL CIRCUIT OPEN
Turn 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?
Yes
No