GM Service Manual Online
For 1990-2009 cars only

Diagnostic Aids

In order to avoid a misdiagnosis, inspect for proper operation of the brake lamps. Refer to Exterior Lighting Systems Description and Operation in Lighting Systems.

For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Electromagnetic Interference on the vehicle speed sensor signal circuit may cause erratic cruise control operation.

Conditions for Enabling Cruise Control

    • The vehicle speed is greater than 40 km/h (25 mph).
    • The vehicle is not in PARK, REVERSE, NEUTRAL, or 1st gear.
    • The system voltage is within 9.2 volts and 16 volts.
    • The park brake is released.
    • The forward looking sensor (FLS) radar is radiating and has identified a stationary or moving object.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step tests the cruise control switch supply voltage circuit for an open, for a short to ground, or for a high resistance.

Step

Action

Values

Yes

No

Schematic Reference : Cruise Control Schematics

Connector End View Reference: Cruise Control Connector End Views or Engine Control Module Connector End Views in Engine Controls - 4.6L

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Turn the cruise control On/Off switch ON.
  4. With the scan tool, observe the Cruise Control Switch parameter in the body control module (BCM) data list.

Does the Cruise Control Switch parameter display On?

--

Go to Step 3

Go to Step 5

3

  1. Press and hold the cruise control set/decrease button.
  2. With the scan tool, observe the Cruise Control Switch parameter in the BCM data list.

Does the Cruise Control Switch parameter display Set?

--

Go to Step 4

Go to Step 9

4

  1. Press and hold the resume/increase switch.
  2. With the scan tool, observe the Cruise Control Switch parameter in the BCM data list.

Does the Cruise Control Switch parameter Display Resume?

--

Go to Diagnostic Aids

Go to Step 9

5

  1. Turn OFF the ignition.
  2. Disconnect the cruise control switch.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the cruise control switch supply voltage circuit and a good ground.

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 11

6

  1. Turn OFF the ignition.
  2. Connect the cruise control switch.
  3. Disconnect C7.
  4. Turn ON the ignition, with the engine OFF.
  5. Turn the cruise control switch ON.
  6. Measure the voltage at the cruise control switch signal circuit.

Does the voltage measure at or near the specified value?

B+

Go to Step 7

Go to Step 8

7

Test the cruise control switch signal circuit for an open or for a short to ground between C7 and the BCM. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 10

8

Test the cruise control switch signal circuit for an open or for a short to ground between C7 and the cruise control switch. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 9

9

Inspect for poor connections at the harness connector of the cruise control switch. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 12

10

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

Did you find and correct the condition?

--

Go to Step 14

Go to Step 13

11

Repair the open, the high resistance or the short to ground in the cruise control switch supply voltage circuit. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 14

--

12

Replace the cruise control switch. Refer to Turn Signal Multifunction Switch Replacement in Steering Wheel and Column.

Did you complete the replacement?

--

Go to Step 14

--

13

Replace the BCM. Refer to Body Control Module Replacement in Computer/Integrating Systems.

Did you complete the replacement?

--

Go to Step 14

--

14

Operate the vehicle within the conditions for cruise control operation.

Does the cruise control system operate properly?

--

System OK

Go to Step 2