DTC Troubleshooting: P0504 (159-1)

DTC P0504: Brake Pedal Position Switch Circuit Malfunction Turn the ignition switch ON (II). 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 | - | Check the brake pedal position switch, then go to Step 29 .
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 .
Release the brake pedal. 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 .
Check BRAKE PEDAL POSITION SWITCH A in the DATA LIST with the HDS. Is OFF indicated?
YES | - | Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the brake pedal position switch and at the ECM.■
NO | - | Check the brake pedal position switch, then go to Step 29 .
Check the brake lights. Do the brake lights come on?
YES | - | Go to Step 8 .
NO | - | Go to Step 12 .
Turn the ignition switch OFF, and wait 30 seconds. Disconnect the brake pedal position switch 4P connector. Disconnect ECM connector No. 2 (58P). 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 30 .
Turn the ignition switch OFF. Disconnect the brake pedal position switch 4P connector. |

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 .
Check No. 13 HORN, STOP (20 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 No. 13 HORN, STOP (20 A) fuse, then go to Step 30 .
NO | - | Repair short in the wire between the brake pedal position switch and No. 13 HORN, STOP (20 A). Also replace No. 13 HORN, STOP (20 A), then go to Step 30 .
Turn the ignition switch OFF, and wait 30 seconds. Disconnect ECM connector No. 2 (58P). 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 30 .
NO | - | Go to Step 19 .
Check the brake pedal position switch. Is the brake pedal position switch OK?
YES | - | Go to Step 34 .
NO | - | Adjust or replace the brake pedal position switch, then go to Step 30 .
Turn the ignition switch OFF. Disconnect the brake pedal position switch 4P connector. Turn the ignition switch ON (II). |

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 .
Check No. 18 IG ACG (15 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 No. 18 IG ACG (15 A) fuse, then go to Step 29 .
NO | - | Repair short in the wire between the brake pedal position switch and No. 18 IG ACG (15 A). Also replace No. 18 IG ACG (15 A), then go to Step 29 . Repair short in the wire between ECM connector No. 2 terminal No. 36 and the brake pedal position switch, then go to Step 29 .
Turn the ignition switch OFF, and wait 30 seconds. Disconnect ECM connector No. 2 (58P). |

Check for continuity between ECM connector No. 2 terminal No. 36 and brake pedal position switch 4P connector terminal No. 4. 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 30 .
Check the brake pedal position switch. Is the brake pedal position switch OK?
YES | - | Go to Step 34 .
NO | - | Adjust or replace the brake pedal position switch, then go to Step 30 .
Turn the ignition switch OFF. Reconnect all connectors. Turn the ignition switch ON (II). Reset the ECM with the HDS. Check for Temporary DTCs or DTCs with the HDS. Are any Temporary DTCs or DTCs indicated?
YES | - | If DTC P0504 is indicated, check for poor connections or loose terminals at the brake pedal position switch and the ECM, then go to Step 1 . If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.
NO | - | Troubleshooting is complete.■
Update the ECM if it does not have the latest software, or substitute a known-good ECM. Check for Temporary DTCs or DTCs with the HDS. Are any Temporary DTCs or DTCs indicated?
YES | - | If DTC P0504 is indicated, check for poor connections or loose terminals at the brake pedal position switch and the ECM, then go to Step 1 . If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.
NO | - | If the ECM was updated, troubleshooting is complete. If the ECM was substituted, replace the original ECM. ■