Unable To Locate Emergency Light Relay And/Or Blunt Cut Wires - keywords lamp roof beacon snow plow

This PI is being updated to add 2007 models. Please discard PIT3190A.

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

Please be aware of 3 similar emergency lighting packages available. Use GM VISS or the vehicle's RPO label to verify which lighting system the vehicle is equipped with.

1. Roof Beacon RPO's 5G4, TRW, or VYU. If the vehicle has any one of the RPO's it will have a roof beacon package.
2. Emergency Vehicle Lighting RPO 5Y0.
3. Wrecker Lighting RPO 5X7.

1. The Roof Beacon (5G4,TRW,VYU) relay is located at the left side B-pillar behind the trim panel and the blunt cut wires run up the B-pillar into the headliner. SI Doc ID 1250300
2. The Emergency Vehicle Light (5Y0) relay is located near the UBEC plastic cover and the blunt cut wires are attached to the frame cross member behind the cab. SI Doc ID 1370241
3. Wrecker Lighting (5X7) relay is located at the right rear corner of the engine compartment see SI Doc ID 836150 for Electrical Connections. SI Doc ID 1370238

All 3 lighting systems use the same dash mounted switch.

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.