GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The body control module (BCM) monitors the adaptive cruise control (ACC) gap adjustment switch signal circuit to determine the driver selected headway. The gap switch is a momentary contact switch that connects a series of resistors. Each switch state, inactive, up and down, corresponds to a specific resistance value. The BCM determines the switch selection by the voltage drop across the resistor. The BCM sets DTC B3623 when it detects a stuck gap up/down switch.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B3623 Steering Wheel Controls Adaptive Cruise Control (ACC) Gap Up/Down Signal Circuit.

DTC Symptom

DTC Symptom Descriptor

00

General Failure

Conditions for Running the DTC

Ignition is in RUN.

Conditions for Setting the DTC

Gap adjustment switch signal circuit remains in the same state for 1 minute

Action Taken When the DTC Sets

Gap +/- switch remains in the last selected position

Conditions for Clearing the MIL/DTC

    • The DTC becomes history when the fault is no longer present.
    • A History DTC clears after 100 malfunction free ignition cycles.
    • The BCM module receives a clear code command from the scan tool.

Diagnostic Aids

Refer to Testing for Intermittent Conditions and Poor Connections .

Step

Action

Values

Yes

No

Schematic Reference: Cruise Control Schematics

Connector End View Reference: Master Electrical Component List

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Attempt to adjust the Gap Switch parameters up or down.
  4. With a scan tool, observe the ACC Gap Switch parameter in the body control module (BCM) data list.

Does the scan tool display voltage values at or near the specified values for the gap switch up, down, and inactive states?

Up-3.1 V

Down-1.5 V

Inactive-0 V

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the BCM connector C2.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage between the gap adjustment switch signal circuit and a good ground.

Does the voltage measure greater than the specified value?

4 V

Go to Step 4

Go to Step 5

4

Test the gap adjustment switch signal circuit for a short to voltage. Refer to Circuit Testing and to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 9

Go to Step 6

5

Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs .

Did you find and correct the condition?

--

Go to Step 9

Go to Step 7

6

Inspect for poor connections at the harness connector of the steering wheel control switch assembly. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs .

Did you find and correct the condition?

--

Go to Step 9

Go to Step 8

7

Important: Perform the setup procedure for the replacement BCM.

Replace the BCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 9

--

8

Replace the steering wheel control switch assembly. Refer to Steering Wheel Control Switch Assembly Replacement .

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.

Does the DTC reset?

--

Go to Step 2

System OK