GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2001 🢒 Century 🢒 Body and Accessories 🢒 Cruise Control 🢒 Cruise Control Inoperative/Malfunctioning Using J 42958 Cruise Control Tester

Diagnostic Aids

In order to avoid misdiagnosis:

    • Inspect for proper operation of the brake lamps.
    • Visually inspect all fuses relative to the cruise control system.
    • Inspect all connectors for poor terminal retention, corrosion or damage.
    • Inspect the throttle linkage/cable for mechanical binding.
    • Inspect cruise control cable adjustment.
    • EMI on the speed sensor signal circuit may cause erratic operation.

PCM Inhibit

The PCM will inhibit (not allow) cruise control if one or more of the following has occurred:

    • When Park, Reverse, Neutral, or 1st gear is indicated .
    • When certain Diagnostic Trouble Codes (DTC) are stored. Refer to the appropriate DTC(s) in the Service Manual.
    • When an over/undercharged battery condition exists.
    • With low engine RPM.
    • With high engine RPM (Fuel Cut-Off).

The Cruise Control Tester

It has been found that when this Tester is used on some vehicles with high resistance or an open in the cruise control module ground circuit, the Tester's LED(s) will light abnormally. For example, the Brake/Clutch and VSS LED(s) will light normally but the Ignition LED will be dim with the ON/OFF switch in the OFF position. However, with the ON/OFF switch in the ON position only the VSS LED will light. If you come upon the above situation, please check the ground circuit prior to going on with your diagnosis.

Step

Action

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. Connect the J 42958 Cruise Control Tester between the harness connector of the cruise control module and the cruise control module.
  2. Place the cruise control ON/OFF switch in the OFF position.
  3. Turn ON the ignition, with the engine OFF.

Is the IGNITION LED on the J 42958 illuminated?

Go to Step  3

Go to Step  20

3

Is the BRAKE/TCC LED on the J 42958 illuminated?

Go to Step  4

Go to Step  22

4

Is the BRAKE LIGHTS LED on the J 42958 OFF?

Go to Step  5

Go to Step  23

5

Press and release the brake pedal.

Did the BRAKE/TCC LED turn OFF on the J 42958 when each step was performed?

Go to Step  6

Go to Step  25

6

Place the cruise control On/Off switch in the ON position. (Leave this switch on until instructed to turn if off.)

Did the ON/OFF and the INHIBIT/ENABLE LED on the J 42958 illuminate?

Go to Step  7

Go to Step  27

7

Is the CRUISE LAMP LED on the J 42958 illuminated?

Go to Step  8

Go to Step  28

8

Press and release the Set/Coast switch.

Did the SET/COAST LED on the J 42958 illuminate when the Set/Coast switch was pressed, and turn off when the Set/Coast switch was released?

Go to Step  9

Go to Step  31

9

Press and release the Resume/Accel switch.

Did the RESUME/ACC LED on the J 42958 illuminate when the Resume/Accel switch was pressed, and turn off when the Resume/Accel switch was released?

Go to Step  10

Go to Step  32

10

Perform the following sequence:

  1. Press and release the INHIBIT OVERRIDE button on the J 42958 .
  2. Press and release the BRAKE button on the tester.
  3. Press and release the S/C button on the tester.

Did the CRUISE ENGAGE LED illuminate continually after the S/C button was pressed and released?

Go to Step  11

Go to Step  20

11
  1. Observe the throttle lever at the throttle body.
  2. Press and hold the R/A button on the J 42958 for five seconds, and then release it.

Did the throttle move to near wide open, and then return approximately to half throttle when the R/A button on the J 42958 was released?

Go to Step  12

Go to Step  36

12
  1. Observe the throttle lever at the throttle body.
  2. Press and hold the S/C button on the J 42958 for five seconds, and then release it.

Did the throttle move toward closed throttle, and then return to approximately half throttle when the S/C button on the J 42958 was released?

Go to Step  13

Go to Step  36

13
  1. Press and release (tap) the R/A button the J 42958 three times.
  2. Press and release the BRAKE button on the J 42958 .

Did the CRUISE ENGAGE LED on the J 42958 turn off and the throttle return to the closed position?

Go to Step  14

Go to Step  36

14
  1. Raise and support vehicle. Refer to Lifting and Jacking the Vehicle in General Information for service procedure.
  2. Block one of the drive wheels.
  3. Turn ON the ignition, with the engine OFF.
  4. Place the transaxle/transmission selector in Drive.
  5. Observe the VSS LED on J 42958 while rotating the drive wheel that is not blocked, by hand.
  6. Place the transaxle/transmission selector in park.

Did the VSS LED flash while the one drive wheel was rotated?

Go to Step  15

Go to Step  29

15

Does the connector harness of the cruise control module have a wire connected to terminal H?

Go to Step  16

Go to Step  19

16
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Select Powertrain Special Functions and then Output Controls for Cruise Inhibit.

While observing the INHIBIT ENABLE LED of the J 42958 , use the scan tool in order to enable the cruise control.

Did the INHIBIT ENABLE LED on the J 42958 dim when the scan tool was used to enable cruise control?

Go to Step  17

Go to Step  33

17
  1. Turn OFF the ignition.
  2. Disconnect the J 42958 and reconnect the vehicle harness to the cruise control module.
  3. Road test the vehicle over 40 km/h (25 mph).
  4. Operate the cruise control.
  5. Use the scan tool in order to view the cruise inhibit status.

Does the scan tool display enabled above 40 km/h (25 mph)?

Go to Step  18

Go to DTC P1585

18

Did the cruise control set and operate normally?

Go to Diagnostic Aids

Go to Step  36

19
  1. Reconnect all components.
  2. Road test vehicle and operate cruise control.

Does cruise control operate normally?

Go to Diagnostic Aids

Go to Step  36

20

Test for an open, high resistance or short to ground in the ignition voltage circuit of the cruise control module. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step  39

Go to Step  21

21

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

Did you find and correct the condition?

Go to Step  39

Go to Step  36

22

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  39

Go to Step  24

23

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  39

Go to Step  26

24

Repair the open or the short to ground in the cruise release, cancel signal circuit of the cruise control module. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step  39

Go to Step  34

25

Repair the short to voltage in the cruise release, cancel switch signal circuit of the cruise control module. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step  39

Go to Step  34

26

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

Did you find and correct the condition?

Go to Step  39

Go to Step  35

27

Repair the open or the short to ground in the cruise control ON switch signal circuit of the cruise control module. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step  39

Go to Step  37

28

Disconnect the J 42958 from the cruise control module, but leave the vehicle harness connected to the J 42958 .

Did the CRUISE LAMP LED remain OFF when the cruise control module was disconnected?

Go to Step  30

Go to Step  36

29

Test for an open or short to ground or short to B+ in the vehicle speed signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step  39

Go to Step  38

30

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

Did you find and correct the condition?

Go to Step  39

Go to Step  38

31

Test for an open or short to ground in the Set/Coast signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step  39

Go to Step  37

32

Test for an open or short to voltage in the Resume/Accel signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step  39

Go to Step  37

33

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

Did you find and correct the condition?

Go to Step  39

Go to Step  38

34

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

Did you complete the replacement?

Go to Step  39

--

35

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

Did you complete the replacement?

Go to Step  39

--

36

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

Did you complete the replacement?

Go to Step  39

--

37

Replace the cruise control switch. Refer to Multifunction, Turn Signal, and Hazard Switch Replacement - On Vehicle .

Did you complete the replacement?

Go to Step  39

--

38

Important: The PCM must be reprogrammed before replacement.

Replace the PCM.

Refer to Powertrain Control Module Replacement 3.1L or Powertrain Control Module Replacement 3.8L in Engine Controls.

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