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Home >> Chevrolet >> 2001 >> Venture Base, Van Passenger >> Repair and Diagnosis >> External Pages >> Different car >> Section 77 (Engine Controls - Self-Diagnostics - 3.0L) >> Diagnostic Tests >> DTC P0504: Brake Switch Correlation >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: It is normal for the brake switch to transition before the cruise brake switch.
  1. Turn ignition on, engine off. Using scan tool, monitor BRAKE SWITCH and CRUISE BRAKE SWITCH while fully depressing and releasing the brake pedal several times. If cruise brake switch follows brake pedal command, but brake switch doesn't, go to next step. If brake switch follows brake pedal command, but cruise brake switch doesn't, go to step  7 . If brake switch and cruise brake switch follow brake pedal command, go to step  11 .
  2. If BRAKE SWITCH always indicates RELEASED, go to next step. If BRAKE SWITCH always indicates APPLIED, go to step  6 .
  3. If any stop lamp works properly, but BRAKE SWITCH always reads RELEASED, replace ECM. If no stop lamp works properly, go to next step.
  4. Check BRAKE fuse (15-amp). Replace and retest if open. If fuse continues to open, check for a short to ground on Orange wire between underhood fuse block and brake switch. If fuse continues to open when brake pedal is applied, check for a short to ground on Light Blue wires or for a shorted stop lamp bulb. Disconnect stop lamp switch. Connect test light between brake switch connector terminal "A" (Orange wire) and ground. If test light is on, go to next step. If test light is off, repair open in Orange wire between underhood fuse block and brake switch.
  5. Connect jumper between brake switch connector terminals. Using scan tool, monitor BRAKE SWITCH. If BRAKE SWITCH indicates APPLIED, check brake switch connector. If connector is okay, check for misadjusted brake switch. See appropriate CRUISE CONTROL SYSTEMS article in ACCESSORIES & EQUIPMENT. If switch is adjusted correctly, replace brake switch. If BRAKE SWITCH does not indicate APPLIED, repair open in Light Blue wire between brake switch and exterior lamp splice.
  6. If any stop lamp works properly, check Light Blue wire for open between exterior lamp splice and ECM. If wire is okay, replace ECM. If no stop lamp works properly, check Light Blue wire for short to voltage and misadjusted stop lamp switch. See appropriate CRUISE CONTROL SYSTEMS article in ACCESSORIES & EQUIPMENT. If switch is adjusted correctly, replace brake switch.
  7. If CRUISE BRAKE SWITCH always indicates APPLIED, got to next step. If CRUISE BRAKE SWITCH always indicates RELEASED, go to step  10 .
  8. Check CRUISE fuse (2-amp). Replace and retest if open. If fuse continues to open, check for a short to ground on Pink wire and Purple wire. Disconnect cruise brake switch. Connect test light between cruise brake switch connector terminal "A" (Pink wire) and ground. If test light is on, go to next step. If test light is off, repair open in Pink wire between instrument panel fuse block and cruise brake switch.
  9. Connect jumper between cruise brake switch connector terminals. Using scan tool, monitor CRUISE BRAKE SWITCH. If CRUISE BRAKE SWITCH indicates RELEASED, check cruise brake switch connector. If connector is okay, check for misadjusted cruise brake switch. See appropriate CRUISE CONTROL SYSTEMS article in ACCESSORIES & EQUIPMENT. If switch is adjusted correctly, replace cruise brake switch. If CRUISE BRAKE SWITCH indicates APPLIED, check Purple wire between cruise brake switch and ECM for open. If wire is okay, replace ECM.
  10. Disconnect cruise brake switch. Using scan tool, monitor CRUISE BRAKE SWITCH. If CRUISE BRAKE SWITCH indicates APPLIED, check for misadjusted cruise brake switch. See appropriate CRUISE CONTROL SYSTEMS article in ACCESSORIES & EQUIPMENT. If switch is adjusted correctly, replace cruise brake switch. If CRUISE BRAKE SWITCH indicates RELEASED, repair Purple wire shorted to voltage between cruise brake switch and ECM.
  11. Using can tool, closely monitor BRAKE SWITCH and CRUISE BRAKE SWITCH while slowly depressing the brake pedal to the full applied position. If BRAKE SWITCH parameter changes first, then CRUISE BRAKE SWITCH parameter changes within 2 inches of brake pedal travel after BRAKE SWITCH parameter had changes, problem is intermittent. See DIAGNOSTIC AIDS  . If BRAKE SWITCH parameter does not change first, then CRUISE BRAKE SWITCH parameter change within 2 inches of brake pedal travel after BRAKE SWITCH parameter had changes, adjust both brake switches. See appropriate CRUISE CONTROL SYSTEMS article in ACCESSORIES & EQUIPMENT.
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