DTC Troubleshooting: P0504 (159)
  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).