GM Service Manual Online
For 1990-2009 cars only

Diagnostic Aids

To avoid misdiagnosis, inspect for the following:

    • Proper adjustment of the cruise control cable. Refer to Cruise Control Cable Adjustment .
    • Proper operation of brake lamps. Refer to Exterior Lighting Systems Description and Operation in Lighting Systems.
    • Proper operation of the clutch system, if equipped with a manual transmission. Refer to Hydraulic Clutch Description in Clutch.
    • The throttle linkage is not binding.
    • The vehicle speed is greater than 40 km/h (25 mph).
    • The system voltage is within 9-16 volts.

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

Step

Action

Values

Yes

No

Schematic Reference: Cruise Control Schematics

1

Did you perform the Cruise Control Diagnostic System Check?

--

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. Connect a test lamp between the ignition 3 voltage circuit and a good ground.

Does the test lamp illuminate?

--

Go to Step 3

Go to Step 5

3

Connect a test lamp between the ignition 3 voltage circuit and the ground circuit of the cruise control module.

Does the test lamp illuminate?

--

Go to Step 4

Go to Step 31

4

  1. Turn the cruise control On/Off switch OFF.
  2. Individually connect a test lamp between a good ground and each of the following circuits:
  3. • The cruise control on switch signal circuit
    • The cruise control set/coast switch signal circuit
    • The cruise control resume/accel switch signal circuit

Does the test lamp illuminate for any of the signal circuits listed above?

--

Go to Step 16

Go to Step 6

5

  1. Turn the cruise control On/Off switch OFF.
  2. Individually connect a test lamp between battery voltage and each of the following circuits:
  3. • The cruise control on switch signal circuit
    • The cruise control set/coast switch signal circuit
    • The cruise control resume/accel switch signal circuit

Does the test lamp illuminate for any of the signal circuits listed above?

--

Go to Step 17

Go to Step 29

6

  1. Turn the cruise control On/Off switch ON.
  2. Connect a test lamp between the cruise control ON switch signal circuit and a good ground.

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 18

7

  1. Connect a test lamp between the cruise control set/coast switch signal circuit and a good ground.
  2. With the cruise control On/Off switch ON, press and hold the set/coast switch.

Does the test lamp illuminate?

--

Go to Step 8

Go to Step 20

8

  1. Connect a test lamp between the cruise control resume/accelerate switch signal circuit and a good ground.
  2. With the cruise control On/Off switch ON, press and hold the resume/accel switch.

Does the test lamp illuminate?

--

Go to Step 9

Go to Step 21

9

  1. Connect a test lamp between the CHMSL supply voltage/stop lamp supply voltage circuit and a good ground.
  2. Depress the brake pedal.

Does the test lamp illuminate?

--

Go to Step 10

Go to Step 32

10

Is the vehicle equipped with a manual transmission?

--

Go to Step 12

Go to Step 11

11

Connect a test lamp between the TCC brake switch/cruise control release signal circuit and a good ground. Refer to Circuit Testing in Wiring Systems.

Does the test lamp illuminate?

--

Go to Step 13

Go to Step 30

12

Connect a test lamp between the clutch start switch signal circuit and a good ground. Refer to Circuit Testing in Wiring Systems.

Does the test lamp illuminate?

--

Go to Step 13

Go to Step 23

13

Connect a DMM between the cruise control engaged signal circuit and a good ground. Refer to Circuit Testing in Wiring Systems.

Does the DMM display near the specified voltage?

B+

Go to Step 14

Go to Step 22

14

Connect a DMM between the vehicle speed signal circuit and a good ground. Refer to Circuit Testing in Wiring Systems.

Does the DMM display near the specified voltage?

B+

Go to Diagnostic Aids

Go to Step 15

15

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

Did you find and correct the condition?

--

Go to Step 37

Go to Step 28

16

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

Did you find and correct the condition?

--

Go to Step 37

Go to Step 27

17

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

Did you find and correct the condition?

--

Go to Step 37

Go to Step 27

18

Test the cruise control on/off switch signal circuit for an open, for a short to ground, or for a high resistance. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 37

Go to Step 19

19

Test the ignition 3 voltage circuit for an open or for a high resistance between SP 200 and the multifunction switch. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 37

Go to Step 27

20

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

Did you find and correct the condition?

--

Go to Step 37

Go to Step 27

21

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

Did you find and correct the condition?

--

Go to Step 37

Go to Step 27

22

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

Did you find and correct the condition?

--

Go to Step 37

Go to Step 26

23

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

Did you find and correct the condition?

--

Go to Step 37

Go to Step 24

24

Test the TCC brake switch/cruise control release signal circuit for an open or for a high resistance between the stop lamp switch and the clutch start switch. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 37

Go to Step 25

25

Inspect for poor connections at the harness connector of the clutch start 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 37

Go to Step 34

26

Inspect for poor connections at the harness connector of the PCM. 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 37

Go to Step 33

27

Inspect for poor connections at the harness connector of the multifunction 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 37

Go to Step 35

28

Inspect for poor connections at the harness connector of the cruise control module. 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 37

Go to Step 36

29

Repair the open, the high resistance, or the short to ground in the ignition 3 voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 37

--

30

Repair the open or the high resistance in the TCC brake switch/cruise control release signal circuit between S 138 and the cruise control module. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 37

--

31

Repair the open or the high resistance in the ground circuit of the cruise control module. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 37

--

32

Repair the open or the high resistance in the CHMSL supply voltage/stop lamp supply voltage circuit between the underhood fuse block and the cruise control module. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 37

--

33

Important: Program the replacement PCM.

Replace the PCM. Refer to the appropriate procedure:

    •  Powertrain Control Module Replacement in Engine Controls - 2.2L.
    •  Powertrain Control Module Replacement in Engine Controls - 4.3L.

Did you complete the replacement?

--

Go to Step 37

--

34

Replace the clutch start switch. Refer to Clutch Pedal Engine Start Switch Replacement in Clutch.

Did you complete the replacement?

--

Go to Step 37

--

35

Replace the multifunction switch. Refer to Multifunction, Turn Signal, and Hazard Switch Replacement - On Vehicle in Steering Wheel and Column - Standard or to Multifunction, Turn Signal, and Hazard Switch Replacement - On Vehicle in Steering Wheel and Column - Tilt.

Did you complete the replacement?

--

Go to Step 37

--

36

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

Did you complete the replacement?

--

Go to Step 37

--

37

Operate the vehicle within the conditions for cruise control operation.

Does the cruise control system operate correctly?

--

System OK

Go to Step 2