GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

1

Did you perform the Cruise Control Diagnostic System Check?

Go to Step 2

Go to Cruise Control System Check

2

  1. Turn OFF the ignition.
  2. Disconnect the cruise control module.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the ignition positive voltage circuit of the cruise control module with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 3

Go to Step 32

3

Probe the ignition positive voltage circuit of the cruise control module with a test lamp that is connected to the ground circuit of the cruise control module.

Does the test lamp illuminate?

Go to Step 4

Go to Step 33

4

  1. Turn ON the ignition, with the engine OFF.
  2. Turn OFF the cruise control.
  3. Probe the on/off, the set/coast, and the resume/accelerate circuits with a test lamp that is connected to a good ground.

Does the test lamp illuminate on any of the circuits?

Go to Step 14

Go to Step 5

5

  1. Turn ON the ignition, with the engine OFF.
  2. Turn ON the cruise control.
  3. Probe the on/off circuit with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 6

Go to Step 15

6

  1. Probe the set/coast circuit with a test lamp that is connected to a good ground.
  2. Press and hold the SET/COAST switch.

Does the test lamp illuminate?

Go to Step 7

Go to Step 17

7

  1. Probe the resume/accelerate circuit with a test lamp that is connected to a good ground.
  2. Press and hold the RESUME/ACCEL switch.

Does the test lamp illuminate?

Go to Step 8

Go to Step 18

8

Probe the brake circuit with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 9

Go to Step 19

9

Depress the brake pedal while monitoring the test lamp.

Does the test lamp illuminate?

Go to Step 20

Go to Step 10

10

Probe the cruise release circuit with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 21

Go to Step 11

11

Depress the brake pedal while monitoring the test lamp.

Does the test lamp illuminate?

Go to Step 12

Go to Step 22

12

Probe the cruise engaged output circuit with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 13

Go to Step 23

13

  1. Raise and suitably support the vehicle.
  2. Probe the VSS signal circuit with a DMM that is connected to a good ground.
  3. Set the DMM to the AC scale.
  4. Rotate one of the drive wheels.
  5. Observe the DMM.

Does the voltage displayed on the scan tool vary?

Go to Step 31

Go to Step 24

14

Test the circuit that illuminated the test lamp for a short to voltage. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 30

15

Test the on/off circuit for an open or a high resistance. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 16

16

Test the ignition positive voltage circuit for an open or high resistance between the cruise control module and the cruise control switch. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 30

17

Test the set/coast circuit for an open or a high resistance. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 30

18

Test the resume/accelerate circuit for an open or a high resistance. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 30

19

Test the brake circuit for an open or a high resistance. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 25

20

Test the brake switch circuit for a short to voltage. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 25

21

Test the cruise release circuit for a short to voltage. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 26

22

Test the brake switch circuit for an open or a high resistance. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 26

23

Test the cruise engaged output circuit for an open, a high resistance, or a short to voltage. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 29

24

Test the speed sensor circuit for an open or a high resistance. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 29

25

Inspect the brake switch for proper adjustment.

Did you find and correct the condition?

Go to Step 39

Go to Step 27

26

Inspect the brake switch for proper adjustment.

Did you find and correct the condition?

Go to Step 39

Go to Step 28

27

Inspect for poor connections at the harness connector of the brake switch. Refer to Intermittents and Poor Connections Diagnosis and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 34

28

Inspect for poor connections at the harness connector of the brake switch. Refer to Intermittents and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 35

29

Inspect for poor connections at the harness connector of the PCM. Refer to Intermittents and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 36

30

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

Did you find and correct the condition?

Go to Step 39

Go to Step 37

31

Inspect for poor connections at the harness connector of the cruise control module. Refer to Intermittents and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 38

32

Repair the ignition positive voltage circuit of the cruise control module. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 39

--

33

Repair the ground circuit of the cruise control module. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 39

--

34

Replace the brake switch. Refer to Stop Lamp Switch Replacement .

Did you complete the replacement?

Go to Step 39

--

35

Replace the brake switch. Refer to Stop Lamp Switch Replacement .

Did you complete the replacement?

Go to Step 39

--

36

Replace the PCM. Refer to VCM Replacement/Programming in Engine Controls.

Did you complete the replacement?

Go to Step 39

--

37

Replace the cruise control switch. Refer to Cruise Control Engagement Switch.

Did you complete the replacement?

Go to Step 39

--

38

Replace the cruise control module. Refer to Cruise Control Module Replacment.

Did you complete the replacement?

Go to Step 39

--

39

Operate the vehicle within the conditions for cruise control operation.

Does the cruise control system operate correctly?

System OK

Go to Step 2