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. |
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 | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Cruise Control Diagnostic System Check? | -- | Go to Step 2 | |
2 |
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:
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 |
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 |
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 |
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 |
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 |
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 |
Does the scan tool display enabled above 40 km/h (25 mph)? | -- | Go to Step 18 | Go to Diagnostic System Check - Engine Controls 3.4L or Diagnostic System Check - Engine Controls 3.8L in Engine Controls |
18 | Did the cruise control set and operate normally? | -- | Go to Diagnostic Aids | Go to Step 36 |
19 |
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 Cruise Release Switch Adjustment for service procedure. 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 for service procedure. 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) input 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 input 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 input 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/OFF input 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 input 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 output 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 input 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 input 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 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 |
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 Steering Wheel Control Switches Replacement in Entertainment or Multifunction Turn Signal Lever Replacement - On Vehicle in Steering Wheel and Column - Tilt . Did you complete the replacement? | -- | Go to Step 39 | -- |
38 |
Important: The PCM must be reprogrammed before replacement. Refer to Powertrain Control Module Programming 3.4L or Powertrain Control Module Programming 3.8L Replace the PCM. Refer to Powertrain Control Module Replacement 3.4L or DTC P0172 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 Diagnostic Aids |
