B2556

DTC B2556

CIRCUIT DESCRIPTION
When the park lamps are on and night time conditions exist, the driver may slide the IP dimmer switch back and forth to adjust the intensity of the interior back lighting. The IP dimmer switch is a rheostat that provides the dash integration module (DIM) with an input signal for the desired dimming intensity. The DIM supplies the 5 volt reference and signal return circuits to the IP dimmer switch. The IP dimmer signal circuit is a direct input to the DIM. The DIM uses a smart driver to monitor the input voltage of the IP dimmer switch, if the voltage is not within the normal operating range the DTC B2556 will set.

CONDITIONS FOR RUNNING THE DTC
This test is run every 150 milliseconds.

CONDITIONS FOR SETTING THE DTC
The interior lamp rheostat voltage is less than 0.09V or greater than 4.75V on consecutive tests.

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

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

DIAGNOSTIC AIDS
- The following may cause an intermittent:
- Bent terminal
- Backed out terminal
- Damaged terminal
- Poor terminal tension
- Chafed wire
- Broken wire inside the insulation
- When diagnosing for an intermittent short or an open, manipulate the wire harness while watching the test equipment for changes.

TEST DESCRIPTION

Steps 1-2:

Steps 3-5:

Steps 6-10:

Steps 11-16:

The numbers below refer to the step numbers on the diagnostic table.
3. Tests for an open in the rheostat. Slowly move the IP dimmer switch from low intensity to high intensity while observing the Interior DIM POT parameter with the scan tool.
4. Tests for the proper operation of the circuit in the high voltage range.
5. 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.
6. Tests for a short to ground in the 5 volt reference circuit.