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DTC B2578: ALC Headlight Relay Output Short To Battery: Testing

  1. If BFC diagnostic system check was performed, go to next step. If BFC diagnostic system check was not performed, see procedures in BFC DIAGNOSTIC SYSTEM CHECK  .
  2. Remove ALC headlight relay from underhood wiring harness junction block. Replace ALC headlight relay with a known-good relay. Using scan tool, enable ALC headlight relay. If ALC headlight relay activates, go to step 8). If ALC headlight relay does not activate, go to next step.
  3. Remove ALC headlight relay from underhood wiring harness junction block. Back out underhood wiring harness junction block Brown 68-pin connector C3, terminal C11 (Pink/White wire). Using DVOM, check voltage between underhood wiring harness junction block connector C3, terminal C11 (Pink/White wire) and ground. If reading is zero volts, go to step 5). If reading is not zero volts, go to next step.
  4. Replace underhood wiring harness junction block. Go to step 8).
  5. Disconnect BFC Gray 16-pin connector C1, terminal A1 (Pink/White wire). Using DVOM, check voltage between underhood wiring harness junction block connector C3, terminal C11 (Pink/White wire) and ground. If reading is zero volts, go to next step. If reading is not zero volts, go to step 7).
  6. Replace BFC. See REMOVAL & INSTALLATION  . Go to step 8).
  7. Repair short to battery in Pink/White wire between BFC connector C1 and underhood wiring harness junction block connector C3. Go to next step.
  8. Clear DTCs. Perform BFC DIAGNOSTIC SYSTEM CHECK  .


  1. If BFC diagnostic system check was performed, go to next step. If BFC diagnostic system check was not performed, see procedures in BFC DIAGNOSTIC SYSTEM CHECK  .
  2. Remove ALC headlight relay from underhood wiring harness junction block. Replace ALC headlight relay with a known-good relay. Using scan tool, enable ALC headlight relay. If ALC headlight relay activates, go to step 8). If ALC headlight relay does not activate, go to next step.
  3. Remove ALC headlight relay from underhood wiring harness junction block. Back out underhood wiring harness junction block Brown 68-pin connector C3, terminal C11 (Pink/White wire). Using DVOM, check voltage between underhood wiring harness junction block connector C3, terminal C11 (Pink/White wire) and ground. If reading is zero volts, go to step 5). If reading is not zero volts, go to next step.
  4. Replace underhood wiring harness junction block. Go to step 8).
  5. Disconnect BFC Gray 16-pin connector C1, terminal A1 (Pink/White wire). Using DVOM, check voltage between underhood wiring harness junction block connector C3, terminal C11 (Pink/White wire) and ground. If reading is zero volts, go to next step. If reading is not zero volts, go to step 7).
  6. Replace BFC. See REMOVAL & INSTALLATION  . Go to step 8).
  7. Repair short to battery in Pink/White wire between BFC connector C1 and underhood wiring harness junction block connector C3. Go to next step.
  8. Clear DTCs. Perform BFC DIAGNOSTIC SYSTEM CHECK  .
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