GM Service Manual Online
For 1990-2009 cars only

Diagnostic Aids

Important: Perform the following in order to avoid misdiagnosis.

    • Inspect for proper operation of brake lamps.
    • Inspect throttle linkage for mechanical binding which could cause the system to malfunction.
    • Inspect cruise control cable adjustment, should have minimum slack.
    • When testing vehicles equipped with steering wheel controls, the steering wheel must be rotated to each stop position while testing the cruise control switch signal circuits. This will assure the integrity of the SIR coil.
    • EMI on the speed sensor signal circuit may cause erratic cruise control operation.

Conditions for Enabling Cruise Control

    • When vehicle speed is more than 40 km/h (25 mph)
    • When PARK, REVERSE, NEUTRAL, or 1st gear is not indicated
    • When an over/undercharged battery condition does not exist
    • With normal engine RPM
    • Without high engine RPM fuel cut-off

Step

Action

Value(s)

Yes

No

Schematic Reference: Cruise Control Schematics

1

Did you perform the Diagnostic System Check - Cruise Control?

--

Go to Step 2

Go to Diagnostic System Check - Cruise Control

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 40

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 41

4

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

Does the test lamp illuminate on any of the signal circuits?

--

Go to Step 18

Go to Step 5

5

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

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 19

6

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

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 21

7

  1. Probe the cruise control resume/accelerate switch signal 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 22

8

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

Does the test lamp illuminate?

--

Go to Step 9

Go to Step 23

9

Press the brake pedal while monitoring the test lamp.

Does the test lamp go out?

--

Go to Step 10

Go to Step 24

10

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

Does the test lamp illuminate?

--

Go to Step 25

Go to Step 11

11

Press the brake pedal while monitoring the test lamp.

Does the test lamp illuminate?

--

Go to Step 12

Go to Step 26

12

Probe the cruise control inhibit signal circuit with a test lamp that is connected to B+.

Does the test lamp illuminate?

--

Go to Step 29

Go to Step 13

13

Turn the ignition OFF , reconnect the cruise control module, disconnect the PCM.

Turn the ignition ON, Probe the cruise control inhibit circuit with a DDM to a good ground.

Does it measure near the specified value?

B+

Go to Step 14

Go to Step 30

14

Turn the ignition OFF, reconnect the PCM , Turn the ignition ON and probe the cruise control engaged signal circuit with a DMM that is connected to a good ground.

Does the voltage measure near the specified value?

B+

Go to Step 15

Go to Step 31

15

  1. Turn OFF the ignition.
  2. Disconnect the appropriate BCM harness connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the cruise control cancel signal circuit with a test lamp connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 16

Go to Step 27

16

Press the cruise control cancel switch while monitoring the test lamp.

Does the test lamp illuminate?

--

Go to Step 28

Go to Step 17

17

Check the speedometer for proper operation.

Does the speedometer operate properly?

--

Go to Step 32

Go to Symptoms - Instrument Panel, Gages and Console in Instrument Panel, Gages, and Console

18

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

Did you find and correct the condition?

--

Go to Step 47

Go to Step 38

19

Test the cruise control on switch signal circuit for an open or a high resistance and the set/coast and resume/accel signal circuits 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 47

Go to Step 20

20

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

Did you find and correct the condition?

--

Go to Step 47

Go to Step 38

21

Test the cruise control set/coast signal circuit for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 47

Go to Step 38

22

Test the cruise control resume/accelerate signal circuit for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 47

Go to Step 38

23

Test the cruise control release switch signal circuit for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 47

Go to Step 33

24

Test the cruise control release switch signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 47

Go to Step 33

25

Test the stop lamp switch signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 47

Go to Step 34

26

Test the stop lamp switch signal circuit for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 47

Go to Step 34

27

Test the cruise control cancel 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 47

Go to Step 38

28

Test the cruise control cancel circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 47

Go to Step 38

29

Test the cruise inhibit signal circuit 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 47

Go to Step 37

30

Test the cruise inhibit signal circuit for an open, a high resistance, or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 47

Go to Step 37

31

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

Did you find and correct the condition?

--

Go to Step 47

Go to Step 37

32

Test the speed sensor circuit for an open or a high resistance between the PCM and cruise control module. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 47

Go to Step 39

33

Inspect the cruise control release switch for proper adjustment. Refer to Stop Lamp Switch Adjustment in Hydraulic Brakes.

Did you find and correct the condition?

--

Go to Step 47

Go to Step 35

34

Inspect the stop lamp switch for proper adjustment. Refer to Stop Lamp Switch Adjustment in Hydraulic Brakes.

Did you find and correct the condition?

--

Go to Step 47

Go to Step 36

35

Inspect for poor connections at the harness connector of the cruise control release 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 47

Go to Step 42

36

Inspect for poor connections at the harness connector of the stop lamp 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 47

Go to Step 43

37

Inspect for poor connections at the harness connector of the PCM. 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 47

Go to Step 44

38

Inspect for poor connections at the harness connector of the cruise control 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 47

Go to Step 45

39

Inspect for poor connections at the harness connector of the cruise control module. 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 47

Go to Step 46

40

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 47

--

41

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

Did you complete the repair?

--

Go to Step 47

--

42

Replace the cruise control release switch. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes.

Did you complete the replacement?

--

Go to Step 47

--

43

Replace the stop lamp switch. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes.

Did you complete the replacement?

--

Go to Step 47

--

44

Important: The PCM must be programed before replacement.

Replace the PCM. Refer to Powertrain Control Module Replacement 2.2L or Powertrain Control Module Replacement in Engine Controls-3.4L.

Did you complete the replacement?

--

Go to Step 47

--

45

Replace the cruise control switch. Refer to Steering Wheel Controls Replacement in Steering Wheel and Column.

Did you complete the replacement?

--

Go to Step 47

--

46

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

Did you complete the replacement?

--

Go to Step 47

--

47

Operate the vehicle within the conditions for cruise control operation.

Does the cruise control system operate correctly?

--

System OK

Go to Step 2