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Home >> Cadillac >> 2007 >> Escalade EXT >> Repair and Diagnosis >> External Pages >> Different car >> Section 1344 (Lighting Systems) >> Diagnostic Information and Procedures >> Stop Lamps Malfunction >> Circuit/System Testing >> CHMSL Relay Control Circuit Test
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CHMSL Relay Control Circuit Test

WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the harness connector X5 at the BCM.
  2. Ignition ON, verify the center high mount stop lamp is not on.
    • If the center high mount stop lamp is on, test the CHMSL relay control circuit terminal 5 for a short to voltage. If the circuit tests normal replace the underhood fuse block.
  3. Install a 10A fused jumper wire between the CHMSL relay control circuit terminal 5 and B+. Verify the center high mount stop lamp is on.
    • If the center high mount stop lamp is not on or the fuse in the jumper wire opens, test the CHMSL relay control circuit for a short to ground or an open/high resistance. If the circuit tests normal replace the underhood fuse block.
  4. If all circuits test normal, replace the BCM.
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