DTC Troubleshooting: P0504 (159)
DTC P0504:
 Brake Pedal Position Switch Circuit Malfunction
NOTE: Before you troubleshoot, record all freeze data and review the general troubleshooting information.
  1. Turn the ignition switch ON (II).
  1. Check BRAKE PEDAL POSITION SWITCH B in the DATA LIST with the HDS when the brake pedal pressed.
Is ON indicated?
YES -
Go to Step 3 .
NO -
  1. Check BRAKE PEDAL POSITION SWITCH A in the DATA LIST with the HDS when the brake pedal pressed.
Is ON indicated?
YES -
Go to Step 4 .
NO -
Go to Step 7 .
  1. Release the brake pedal.
  1. Check BRAKE PEDAL POSITION SWITCH B in the DATA LIST with the HDS.
Is OFF indicated?
YES -
Go to Step 6 .
NO -
Go to Step 20 .
  1. Check BRAKE PEDAL POSITION SWITCH A in the DATA LIST with the HDS.
Is OFF indicated?
YES -
Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the brake pedal position switch and the ECM.■
NO -
  1. Check the brake lights.
Do the brake lights come on?
YES -
Go to Step 8 .
NO -
Go to Step 12 .
  1. Turn the ignition switch OFF, and wait 2 minutes.
  1. Disconnect the brake pedal position switch 4P connector.
  1. Disconnect ECM connector No. 2 (58P).
  1. Check for continuity between ECM connector No. 2 terminal No. 38 and brake pedal position switch 4P connector terminal No. 2.
Is there continuity?
YES -
Go to Step 34 .
NO -
Repair open in the wire between the brake pedal position switch and ECM connector No. 2 terminal No. 38, then go to Step 29 .
  1. Turn the ignition switch OFF.
  1. Disconnect the brake pedal position switch 4P connector.
  1. Measure voltage between brake pedal position switch 4P connector terminal No. 1 and body ground.
Is there battery voltage?
YES -
Go to Step 16 .
NO -
Go to Step 15 .
  1. Check the No. 21 HORN, STOP (15 A) fuse in the under-hood fuse/relay box.
Is the fuse OK?
YES -
Repair open in the wire between the brake pedal position switch and the No. 21 HORN, STOP (15 A) fuse, then go to Step 29 .
NO -
Repair short in the wire between the brake pedal position switch and No. 21 HORN, STOP (15 A). Also replace the No. 21 HORN, STOP (15 A), then go to Step 29 .
  1. Turn the ignition switch OFF, and wait 2 minutes.
  1. Disconnect ECM connector No. 2 (58P).
  1. Check for continuity between ECM connector No. 2 terminal No. 38 and body ground.
Is there continuity?
YES -
Repair short in the wire between the brake pedal position switch and ECM connector No. 2 terminal No. 38, then go to Step 29 .
NO -
Go to Step 19 .
Is the brake pedal position switch OK?
YES -
Go to Step 34 .
NO -
  1. Turn the ignition switch OFF.
  1. Disconnect the brake pedal position switch 4P connector.
  1. Turn the ignition switch ON (II).
  1. Measure voltage between brake pedal position switch 4P connector terminal No. 3 and body ground.
Is there battery voltage?
YES -
Go to Step 25 .
NO -
Go to Step 24 .
  1. Check the No. 3 ALTERNATOR (10 A) fuse in the under-dash fuse/relay box.
Is the fuse OK?
YES -
Repair open in the wire between the brake pedal position switch and the No. 3 ALTERNATOR (10 A) fuse, then go to Step 29 .
NO -
  • Repair short in the wire between the brake pedal position switch and No. 3 ALTERNATOR (10 A). Also replace the No. 3 ALTERNATOR (10 A), then go to Step 29 .
  • Repair short in the wire between the ECM connector No. 2 terminal No. 36 and the brake pedal position switch. Also replace the No. 3 ALTERNATOR (10 A), then go to Step 29 .
  1. Turn the ignition switch OFF, and wait 2 minutes.
  1. Disconnect ECM connector No. 2 (58P).
  1. Check for continuity between ECM connector No. 2 terminal No. 36 and brake pedal position switch 4P connector terminal No. 3.
Is there continuity?
YES -
Go to Step 28 .
NO -
Repair open in the wire between the brake pedal position switch and ECM connector No. 2 terminal No. 36, then go to Step 29 .
Is the brake pedal position switch OK?
YES -
Go to Step 34 .
NO -
  1. Turn the ignition switch OFF.
  1. Reconnect all connectors.
  1. Turn the ignition switch ON (II).
  1. Reset the ECM with the HDS.
  1. Check for Temporary DTCs or DTCs with the HDS.
Is DTC P0504 indicated?
YES -
Check for poor connections or loose terminals at the brake pedal position switch and the ECM, then go to Step 1 .
NO -
Troubleshooting is complete. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.■
  1. Reconnect all connectors.
  1. Check for Temporary DTCs or DTCs with the HDS.
Is DTC P0504 indicated?
YES -
Check for poor connections or loose terminals at the brake pedal position switch and the ECM. If the ECM was updated, substitute a known-good ECM, then recheck. If the ECM was substituted, go to Step 1 .
NO -
If the ECM was updated, troubleshooting is complete. If the ECM was substituted, replace the original ECM. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.■