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For 1990-2009 cars only

Blown MBEC 1 or LBEC 1 Fuse - keywords circuit door electrical inoperative lamp LBEC lighting lock MBEC power seat window wire

Subject:Blown MBEC 1 or LBEC 1 Fuse

Models:2003-2006 Cadillac Escalade, Escalade ESV, Escalade EXT
2003-2006 Chevrolet Avalanche, Silverado, Suburban, Tahoe
2003-2006 GMC Sierra, Yukon, Yukon Denali, Yukon XL, Yukon XL Denali



The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:

There have been reports of either the MBEC 1 or LBEC 1 maxi fuse blown intermittently and unable to locate a short to ground.

Recommendation/Instructions:

If after normal diagnostics no shorts can be found the below items have been reported:

  1. "MBEC 1" Maxi Fuse 50 Amp (SI Document ID # 1242532).
  2. If no shorts are located on circuit 642, inspect circuits 1340 after the "Rt Door" circuit breaker 25 amp and circuit 1440 after the "Seat" circuit breaker 30 Amp (SI Document ID # 1242687).

    • Inspect circuit 1340 shorted to ground near the right I/P support bracket.
    • Inspect circuit 1340 or 1440 shorted to ground on the support bracket for the I/P relay block.
    • Inspect circuit 1440 shorted to ground under or in either front seat.
    • Inspect circuit 1440 shorted to ground near the parking brake pedal assembly. The short may only occur if the parking brake pedal is depressed.
  3. "LBEC 1" Maxi Fuse 50 AMP (SI Document ID # 1242532).
  4.  - If no shorts are located on circuit 42 inspect circuit 1240 after the "Lt Door" circuit breaker 25 amp (SI Document ID # 1242687).
     - Inspect circuit 1240 shorted to ground near the parking brake pedal assembly. The short may only occur if the parking brake pedal is depressed.

Note: Replacement of the circuit breaker is needed if a short to ground is found on circuit 3, 1240, 1340, or 1440.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.