Circuit Description
The instrument panel (I/P) dimmer switch is a potentiometer. The HVAC control module determines the control setting based on the voltage from the I/P dimmer switch. The HVAC control module sends out a class 2 message to the dash integration module (DIM). The intensity of the of the interior backlighting shall be adjustable when ever the park lamps are ON. The intensity of the vacuum florescent displays shall only be adjustable when it is low light conditions and the park lamps are active.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2627 Display Dimming Pulse Width Modulation (PWM) Output Circuit Low
Conditions for Running the DTC
The HVAC control module must be powered.
Conditions for Setting the DTC
The feedback voltage is less than 0.2 volts for more than 200 milliseconds.
Action Taken When the DTC Sets
The dimming level is set to full brightness for all displays.
Conditions for Clearing the DTC
The I/P dimmer switch short to ground condition must be corrected.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step tests for the proper operation of the circuit in the high voltage range.
-
This step 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 battery positive voltage.
-
This step tests for a short to ground in the 5-volt reference circuit.
-
This step tests for a short to ground in the twilight sentinel delay signal circuit of the twilight delay switch. A short to ground may set DTC B2627 and DTC B2642 depending position of the I/P dimmer switch.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Interior Lights Dimming Schematics Connector End View Reference: Computer/Integrating Systems Connector End Views in Computer/Integrating Systems or Lighting Systems Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 |
Does the scan tool indicate that the Interior Dim Pot data parameter stays within the specified range? | 0.2-4.8 V | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 |
Does the scan tool indicate that the Interior Dim Pot data parameter is greater than the specified value? | 4.8 V | Go to Step 4 | Go to Step 8 | |
Does the scan tool indicate that the Interior Dim Pot data parameter is less than the specified value? | 0.2 V | Go to Step 5 | Go to Step 9 | |
Does the scan tool indicate that the Interior Dim Pot data parameter is greater than the specified value? | 4.8 V | Go to Step 7 | Go to Step 6 | |
6 | Test the 5-volt reference circuit of the I/P dimmer switch for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 13 |
7 | Test the 5-volt reference circuit of the I/P dimmer switch for a short to voltage, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 11 |
8 | Test the I/P lamps dimmer switch signal circuit of the I/P dimmer switch for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 13 |
9 | Test the I/P lamps dimmer switch signal circuit of the I/P dimmer switch for a short to battery positive voltage, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 10 |
10 | Test the ground circuit of the I/P dimmer switch for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 13 |
Test the twilight sentinel delay signal circuit of the twilight delay switch for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 12 | |
12 | Inspect for poor connections at the harness connector of the headlamp switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 14 |
13 | Inspect for poor connections at the harness connector of the CCP. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 15 |
14 | Replace the headlamp switch. Refer to Headlamp Switch Replacement . Did you complete the replacement? | -- | Go to Step 16 | -- |
15 | Replace the CCP. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 16 | -- |
16 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
