B2620

DTC B2620

CIRCUIT DESCRIPTION
The body control module (BCM) directly sends a 5-volt reference voltage to the instrument panel (I/P) dimmer switch which is then adjusted based on the I/P dimmer switch position and returned as a dimming return and dimming input to the BCM. The BCM uses this signal to directly control the desired level of instrument panel illumination lamp intensity.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC B2620 Display Dimming Pulse Width Modulation (PWM) Input Circuit

CONDITIONS FOR RUNNING THE DTC
The battery voltage must be between 9.0-16.0 volts.

CONDITIONS FOR SETTING THE DTC
- The BCM monitors a dimming return voltage of less than 4.5 volts.
- The BCM monitors a 5-volt reference voltage of greater than 5.5 volts.
- The BCM monitors dimming input voltage of equal or greater than 4.86 volts for more than 1 second.

ACTION TAKEN WHEN THE DTC SETS
The instrument panel illumination lamp dimming will not operate.

CONDITIONS FOR CLEARING THE MIL/DTC
- This DTC will clear on current status after the condition for setting the fault is corrected.
- A history DTC will clear after 100 consecutive ignition cycles without a fault present.
- History and current DTCs can be cleared using a scan tool.

TEST DESCRIPTION

Steps 1-10:

Steps 11-16:

The numbers below refer to the step numbers on the diagnostic table.
3. This step tests for the proper operation of the circuit in the low voltage range.
4. This step tests for the proper operation of the circuit in the high voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to ground.
5. This step tests for a short to voltage in the 5-volt reference circuit.
6. This step tests for a high resistance or an open in the dimming return circuit.