B2556

DTC B2556

CIRCUIT DESCRIPTION
The I/P dimmer switch is a potentiometer. The instrument panel module (IPM) determines the control setting based on the voltage from the I/P dimmer switch. The IPM sends out a class 2 message to the dash integration module (DIM). The intensity of the of the backlighting is adjustable when ever the park lamps are on. The intensity of the vacuum florescent displays are only adjustable when it is night and the park lamps are active.

CONDITIONS FOR RUNNING THE DTC
The IPM is powered.

CONDITIONS FOR SETTING THE DTC
The I/P dimmer switch voltage is less than 0.09 volts or greater than 4.95 volts.

ACTION TAKEN WHEN THE DTC SETS
Set dimming level to 100 percent full brightness for all displays.

CONDITIONS FOR CLEARING THE DTC
The IPM does not detect a voltage that is less than or greater than the predetermined value during the diagnostic self test.

TEST DESCRIPTION

Steps 1-2:

Steps 3-4:

Steps 5-8:

Steps 9-15:

The numbers below refer to the step numbers on the diagnostic table.
3. Tests for the proper operation of the circuit in the high voltage range.
4. Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.
5. Tests for a short to ground in the 5 volt reference circuit.