GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2004 🢒 Isuzu MD F-Series 🢒 Accessories 🢒 Cruise Control 🢒 Cruise Control Inoperative/Malfunctioning

Diagnostic Aids

In order to avoid a misdiagnosis, inspect for the following:

    • Proper operation of the stop lamps, refer to Exterior Lighting Systems Description and Operation in Lighting Systems.
    • Proper adjustment of the stop lamps, refer to Stop Lamp Switch Adjustment in Lighting Systems.
    • For an intermittent, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
    • EMI on the speed sensor signal circuit may cause erratic cruise control operation.

Conditions for Enabling Cruise Control
    • The vehicle speed is greater than 40 km/h (25 mph).
    • The vehicle is not in PARK, REVERSE, NEUTRAL, or 1st gear.
    • The system voltage is between 12 volts and 16 volts.

Test Description

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

  1. This step checks for a short to voltage on the cruise control on switch signal circuit.

    2.

  2. This step checks for an open or for a high resistance on the cruise control on switch signal circuit between the multifunction switch and S254.

    3.

  3. This step checks for a short to ground, an open, or for a high resistance on the cruise control set/coast switch signal circuit.

    4.

  4. This step checks for a short to ground, an open, or for a high resistance on the cruise control resume/accel switch signal circuit.

    5.

  5. This step checks for a short to ground, an open, or for a high resistance on the ignition 1 voltage circuit.

    6.

  6. This step checks for open or for a high resistance on the cruise control cancel signal circuit between the brake switch relay and the ECM.

    7.

  7. This step checks for a short to voltage on the cruise control cancel signal circuit.

    8.

  8. This step checks for a short to ground, an open, or for a high resistance on the clutch pedal position switch signal circuit.

    9.

  9. This step checks for a short to voltage on the clutch pedal position switch signal circuit.

    10.

  10. This step checks for a short to ground, an open, or for a high resistance on the cruise control on switch signal circuit.

Step

Action

Yes

No

Schematic Reference: Cruise Control Schematics

Connector End View Reference: Engine Controls Connector End Views or to Manual Transmission Connector End Views in Manual Transmission - Medium Duty

1

Did you perform the Diagnostic System Check - Cruise Control?

Go to Step 2

Go to Diagnostic System Check - Cruise Control

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Turn the AUTO CRUISE on/off switch OFF.
  4. With the scan tool, observe the Cruise On/Off Switch parameter in the PCM Engine 1 Data, data list.

Does the Cruise On/Off Switch parameter display Off?

Go to Step 3

Go to Step 7

3
  1. Turn the AUTO CRUISE on/off switch ON.
  2. With the scan tool, observe the Cruise On/Off Switch parameter.

Does the Cruise On/Off Switch parameter display On?

Go to Step 4

Go to Step 22

4
  1. With the scan tool, observe the Cruise Set/Coast Switch parameter in the PCM Engine 1 Data, data list.
  2. Turn the AUTO CRUISE on/off switch ON.
  3. Press and hold the cruise control set/coast switch.

Does the Cruise Set/Coast Switch parameter display On?

Go to Step 5

Go to Step 8

5
  1. With the scan tool, observe the Cruise Resume/Accel. Switch parameter in the PCM data list.
  2. Turn the AUTO CRUISE on/off switch ON.
  3. Activate and hold the resume/accel switch.

Does the Cruise Resume/Accel. Switch parameter display On?

Go to Step 6

Go to Step 10

6

Do the stop lamps operate properly?

Go to Step 11

Go to Stop Lamps Always On or to Stop Lamps Inoperative in Lighting Systems

7

  1. Turn OFF the ignition.
  2. Disconnect the AUTO CRUISE on/off switch.
  3. Turn ON the ignition, with the engine OFF.
  4. With the scan tool, observe the Cruise On/Off Switch parameter.

Does the Cruise On/Off Switch parameter display On?

Go to Step 26

Go to Step 35

8

  1. Turn OFF the ignition.
  2. Disconnect C1 of the multifunction 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 9

Go to Step 37

9

  1. Turn OFF the ignition.
  2. Connect a 3-ampere fused jumper between the cruise control set/coast switch signal circuit and the ignition 1 voltage circuit.
  3. Turn ON the ignition, with the engine OFF.
  4. With the scan tool, observe the Cruise Set/Coast Switch parameter.

Does the Cruise Set/Coast Switch parameter display On?

Go to Step 32

Go to Step 28

10

  1. Turn OFF the ignition.
  2. Disconnect C2 of the multifunction switch.
  3. Connect a 3-ampere fused jumper between the cruise control resume/accel switch signal circuit and the ignition 1 voltage circuit.
  4. Turn ON the ignition, with the engine OFF.
  5. With the scan tool, observe the Cruise Resume/Accel. Switch parameter.

Does the Cruise Resume/Accel. Switch parameter display On?

Go to Step 32

Go to Step 29

11

With the scan tool, observe the Stoplamp Pedal Switch parameter in the PCM Engine 1 Data, data list.

Does the Stoplamp Pedal Switch parameter display Applied?

Go to Step 12

Go to Step 14

12

  1. Turn OFF the ignition.
  2. Remove the brake switch relay.
  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 13

Go to Step 36

13

  1. Turn OFF the ignition.
  2. Connect a 3-ampere fused jumper between the cruise control cancel signal circuit and the ignition 1 voltage circuit.
  3. Turn ON the ignition, with the engine OFF.
  4. With the scan tool, observe the Stoplamp Switch parameter.

Does the Stoplamp Pedal Switch parameter display Released?

Go to Step 38

Go to Step 24

14
  1. With the scan tool, observe the Stoplamp Pedal Switch parameter in the PCM Engine 1 Data, data list.
  2. Depress the brake pedal.

Does the Stoplamp Pedal Switch parameter display Applied?

Go to Step 16

Go to Step 15

15

  1. Turn OFF the ignition.
  2. Remove the brake switch relay.
  3. Turn ON the ignition, with the engine OFF.
  4. With the scan tool, observe the Stoplamp Switch parameter.

Does the Stoplamp Pedal Switch parameter display Applied?

Go to Step 38

Go to Step 25

16

Is the vehicle equipped with a manual transmission?

Go to Step 17

Go to Diagnostic Aids

17

With the scan tool, observe the Clutch Pedal Switch parameter in the PCM Engine 1 Data, data list.

Does the Clutch Pedal Switch parameter display Released?

Go to Step 19

Go to Step 18

18
  1. Turn OFF the ignition.
  2. Disconnect the clutch pedal position (CPP) 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 20

Go to Step 36

19
  1. With the scan tool, observe the Clutch Pedal Switch parameter in the PCM Engine 1 Data, data list.
  2. Depress the clutch pedal.

Does the Clutch Pedal Switch parameter display Applied?

Go to Diagnostic Aids

Go to Step 21

20

  1. Turn OFF the ignition.
  2. Connect a 3-ampere fused jumper between the ignition 1 voltage circuit and the clutch pedal position switch signal circuit.
  3. Turn ON the ignition, with the engine OFF.
  4. With the scan tool, observe the Clutch Pedal Switch parameter in the PCM Engine 1 Data, data list.

Does the Clutch Pedal Switch parameter display Released?

Go to Step 33

Go to Step 31

21

  1. Turn OFF the ignition.
  2. Disconnect the clutch pedal position (CPP) switch.
  3. Turn ON the ignition, with the engine OFF.
  4. With the scan tool, observe the Clutch Pedal Switch parameter in the PCM Engine 1 Data, data list.

Does the Clutch Pedal Switch parameter display Released?

Go to Step 30

Go to Step 33

22
  1. Turn OFF the ignition.
  2. Disconnect the AUTO CRUISE on/off 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 23

Go to Step 36

23

  1. Turn OFF the ignition.
  2. Connect a 3-ampere fused jumper between the ignition 1 voltage circuit and the cruise control on signal circuit.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Cruise On/Off Switch parameter in the PCM Engine 1 Data, data list.

Does the Cruise On/Off Switch parameter display On?

Go to Step 35

Go to Step 27

24

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

Did you find and correct the condition?

Go to Step 43

Go to Step 34

25

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 43

Go to Step 34

26

Test the cruise control on 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 43

Go to Step 34

27

Test the cruise control on switch 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 43

Go to Step 34

28

Test the cruise control set/coast switch 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 43

Go to Step 34

29

Test the cruise control resume/accel switch 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 43

Go to Step 34

30

Test the clutch pedal position 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 43

Go to Step 34

31

Test the clutch pedal position switch 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 43

Go to Step 34

32

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 43

Go to Step 41

33

Inspect for poor connections at the harness connector of the CPP 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 43

Go to Step 40

34

Inspect for poor connections at the harness connector of the ECM. 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 43

Go to Step 42

35

Inspect for poor connections at the harness connector of the AUTO CRUISE on/off 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 43

Go to Step 39

36

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

Did you complete the repair?

Go to Step 43

--

37

Repair the open or the high resistance in the cruise control on signal circuit between the multifunction switch and S254. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 43

--

38

Replace the brake switch relay.

Did you complete the replacement?

Go to Step 43

--

39

Replace the AUTO CRUISE on/off switch. Refer to Cruise Control Switch Replacement .

Did you complete the replacement?

Go to Step 43

--

40

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

Did you complete the replacement?

Go to Step 43

--

41

Replace the multifunction switch. Refer to Turn Signal Multifunction Switch Replacement in Steering Wheel and Column.

Did you complete the replacement?

Go to Step 43

--

42

Important: Program the replacement ECM.

Replace the ECM. Refer to Engine Control Module Replacement/Restore Fuel Rate Data in Engine Controls - 7.8 L.

Did you complete the replacement?

Go to Step 43

--

43

Operate the vehicle within the conditions for cruise control operation.

Does the cruise control system operate properly?

System OK

Go to Step 2