After all DTCs have been displayed, BCM provides individual input and output diagnostic checks for all functions. All systems (except interior lights, tamper signal and RKE input) will indicate each change in system status (i.e., driver's door opened) with a single flash and chime bong. If the proper feedback is not received, then there is an open or short in that circuit or a faulty component.
While in diagnostics, if any button is pressed on RKE transmitter, a chime should be heard to indicate Remote Control Door Lock Receiver (RCDLR) module received a signal from transmitter and sent it on to BCM.
Interior lights are connected in parallel. If lights are all turned off, then any light is turned on, a chime will sound. To further test interior lights, tamper signal and additional outputs, change headlight switch from an inactive to an active state to allow BCM to go through cycles. See INTERIOR LIGHTS/TAMPER SIGNAL INPUT/OUTPUT DIAGNOSTIC table. Each time headlight switch is changed from an inactive to an active state, BCM goes to next cycle and chime bongs to let technician know what cycle BCM is in.

INTERIOR LIGHTS/TAMPER SIGNAL INPUT/OUTPUT DIAGNOSTIC

Cycle No.

Action

Battery Output To Courtesy Lights Deactivated

Battery Output To Courtesy Lights Activated

⁽¹⁾ If Mileage Flag Is Set, Courtesy Output Is Inactive, Then Activated For One Second

4 ⁽²⁾

Parking Lights Activated For One Second

5 ⁽²⁾

Horn Activated For 0.5 Second

6 ⁽²⁾

Shock Sensor Diagnostics Enabled & Security Warning Indicator Turned On

7 ⁽²⁾

Shock Sensor Diagnostics Disabled & Security Warning Indicator Turned Off

⁽¹⁾	Interior lights will change state when this occurs

⁽²⁾	BCM-4 only

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Input/Output Diagnostics