GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2006 🢒 Grand Prix 🢒 Accessories 🢒 Navigation Systems 🢒 DTC B3621

Circuit Description

The head-up display (HUD) detects that the HUD Information Down signal circuit is low for greater than 60 seconds. The HUD monitors the switch signal circuits in order to perform various functions. The HUD switch contains 3 active low momentary switches, and a variable resistor. The HUD detects a switch activation when the signal circuit is active.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B3621 Head Up Display (HUD) Information Down Switch Circuit

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

The HUD detects that the HUD Info Down signal circuit is low for greater than 60 seconds.

Action Taken When the DTC Sets

The HUD ignores the malfunctioning switch circuit.

Conditions for Clearing the DTC
    • The current DTC clears when fault is no longer present but all history codes remain.
    • The HUD receives a clear code command from the scan tool.

Step

Action

Yes

No

Schematic Reference: Head Up Display Schematics

1

Did you review the operation and perform the necessary inspections?

Go to Step 2

Go to Symptoms - Instrument Panel, Gages and Console

2
  1. Turn ON the ignition, with the engine ON.
  2. Adjust the head-up display (HUD) UP, then DOWN.

Does the HUD display adjust properly?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3
  1. Turn OFF the ignition.
  2. Disconnect the HUD.
  3. Connect a test lamp between the DOWN control circuit and ground. Refer to Circuit Testing in Wiring Systems.
  4. Move the HUD up/down switch to the DOWN position.

Does the test lamp illuminate?

Go to Step 7

Go to Step 4

4

Test the HUD DOWN control circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 9

Go to Step 5

5

Inspect for poor connections at the harness connector of the HUD 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 9

Go to Step 6

6

Replace the HUD switch. Refer to Head Up Display Switch Replacement .

Did you complete the replacement?

Go to Step 9

--

7

Inspect for poor connections at the harness connector of the HUD. 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 9

Go to Step 8

8

Replace the HUD. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 9

--

9
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

System OK

Go to Step 2