GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2004 🢒 Grand Prix 🢒 Accessories 🢒 Cruise Control 🢒 Cruise Control Inoperative/Malfunctioning

Diagnostic Aids

Caution: Refer to SIR Caution in the Preface section.

Disable the inflatable restraint steering wheel module when performing this diagnostic table. Refer to SIR Disabling and Enabling in SIR.

Perform the following in order to avoid misdiagnosis:

    • Ensure that the following cruise control switches are not stuck in the engaged position:
      • On/Off switch
      • Set/Coast switch
      • Resume/Accel switch
    • Inspect for proper operation of the stop lamps. Refer to Exterior Lighting Systems Description and Operation in Wiring Systems.
    • Rotate the steering wheel to both steering stops and activate each cruise control switch separately. With a scan tool, observe the associated Cruise Control Switch parameter in the PCM Cruise Control Data data list. This will help eliminate the possibility of a internally open or shorted inflatable restraint steering wheel module coil.
    • EMI on the speed sensor signal circuit may cause erratic cruise control operation.
    • For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

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

  1. DTCs will set in the PCM when you perform this diagnostic table.

Step

Action

Values

Yes

No

Schematic Reference: Cruise Control Schematics

Connector End View Reference: Powertrain Control Module Connector End Views in Engine Controls -- 3.8L (L26 and L32)

1

Did you perform the Cruise Control Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Cruise Control

2

Is DTC P0573 current in the PCM?

--

Go to DTC P0573 in Lighting Systems

Go to Step 3

3
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Turn the cruise control On/Off switch OFF.
  4. With the scan tool, observe the following cruise control parameters in the Cruise Control data list:
    5. • Cruise On/Off Switch
    • Cruise Resume/Accel Switch
    • Cruise Set/Coast Switch

Do any of the parameters listed above display On?

--

Go to Step 13

Go to Step 4

4
  1. With the scan tool, observe the Cruise On/Off Switch parameter.
  2. Turn the cruise On/Off switch ON.

Does the Cruise On/Off Switch parameter display On?

--

Go to Step 5

Go to Step 14

5
  1. With the scan tool, observe the Cruise Set/Coast Switch parameter.
  2. Press and hold the set/coast switch.

Does the Cruise Set/Coast Switch parameter display On?

--

Go to Step 6

Go to Step 21

6
  1. With the scan tool, observe the Cruise Resume/Accel Switch parameter.
  2. Press and hold the resume/accel switch.

Does the Cruise Resume/Accel Switch parameter display On?

--

Go to Step 7

Go to Step 21

7
  1. Turn OFF the ignition.
  2. Disconnect C3 at the body control module.
  3. Turn ON the ignition, with the engine OFF.
  4. With a DMM, measure the voltage of the cruise control cancel signal circuit.

Does the voltage measure at or greater than the specified voltage?

0.5 V

Go to Step 12

Go to Step 8

8
  1. Activate and hold the cruise control cancel switch.
  2. With a DMM, measure the voltage of the cruise control cancel signal circuit.

Does the voltage measure at the specified voltage?

B+

Go to Step 9

Go to Step 20

9
  1. Turn OFF the ignition.
  2. Connect C3 at the BCM.
  3. Disconnect the throttle actuator control (TAC) module.
  4. Turn ON the ignition, with the engine OFF.
  5. With a DMM, measure the voltage of the vehicle speed signal circuit.

Does the voltage measure greater than the specified value?

8.5 V

Go to Step 10

Go to Step 17

10

Test the vehicle speed signal circuit 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 29

Go to Step 11

11

With a DMM, measure the voltage of the stop lamp switch signal circuit.

Does the voltage measure greater than the specified value?

8.5 V

Go to Step 23

Go to Step 24

12

Test the cruise control cancel signal circuit 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 29

Go to Step 21

13
  1. Turn OFF the ignition.
  2. Disconnect the cruise switch.
  3. Turn ON the ignition, with the engine OFF.
  4. With the scan tool, observe the following cruise control parameters:
    5. • Cruise On/Off Switch
    • Cruise Resume/Accel Switch
    • Cruise Set/Coast Switch

Do any of the parameters listed above display On?

--

Go to Step 18

Go to Step 21

14
  1. Turn OFF the ignition.
  2. Disconnect the cruise switch.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the ignition 1 voltage circuit and a good ground.

Does the test lamp illuminate?

--

Go to Step 15

Go to Step 25

15

Test the ignition 1 voltage circuit for an open or for a high resistance between C201 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 29

Go to Step 16

16
  1. Turn OFF the ignition.
  2. Connect a 3 ampere fused jumper between the ignition 1 voltage circuit and the cruise control set/coast and resume/accelerate switch signal circuit.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Cruise Mode Signal parameter in the PCM Cruise Control data list.

Does the Cruise Mode Signal parameter display at or greater than the specified voltage?

4.5 V

Go to Step 21

Go to Step 19

17

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 29

Go to Step 22

18

Test the cruise control set/coast and resume/accel switch signal circuit 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 29

Go to Step 22

19

Test the cruise control set/coast and 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 29

Go to Step 22

20

Test the cruise control cancel signal circuit for a short to ground, 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 29

Go to Step 21

21

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 29

Go to Step 26

22

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 29

Go to Step 28

23

Inspect for poor connections at the harness connector of the TAC 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 29

Go to Step 27

24

Repair the open or the high resistance in the stop lamp switch signal circuit between the underhood fuse block and the TAC module. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 29

--

25

Repair the open, the short to ground, or the high resistance in the ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 29

--

26

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

Did you complete the replacement?

--

Go to Step 29

--

27

Replace the TAC module. Refer to Throttle Body Assembly Replacement in Engine Controls -- 3.8L (L26 and L32).

Did you complete the replacement?

--

Go to Step 29

--

28

Important: Program the replacement PCM.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls -- 3.8L (L26 and L32).

Did you complete the replacement?

--

Go to Step 29

--

29

  1. Enable the inflatable restraint steering wheel module. Refer to SIR Disabling and Enabling in SIR.
  2. Use the scan tool in order to clear the PCM DTCs.
  3. Operate the cruise control system in order to verify the repair.

Does the cruise control system operate properly?

--

System OK

Go to Step 2