Diagnostic System Check - Cruise Control

Cruise Control On-Board Diagnostic (OBD) System Check:

Cruise Control On-Board Diagnostic (OBD) System Check (Part 1 Of 4):

Cruise Control On-Board Diagnostic (OBD) System Check (Part 2 Of 4):

Cruise Control On-Board Diagnostic (OBD) System Check (Part 3 Of 4):

Cruise Control On-Board Diagnostic (OBD) System Check (Part 4 Of 4):

SYSTEM DESCRIPTION
The cruise control OBD system check is an organized approach to identifying a problem created by an electronic cruise control system malfunction. It must be the starting point for any cruise control electrical repairs because it directs the service technician to the next logical step. Understanding the diagnostic table and using it correctly will reduce diagnostic time and prevent the unnecessary replacement of functioning components.

When the cruise control switch is moved into the SET/COAST position and the cruise on-off button is pressed, the cruise control module enters a self-diagnostic check mode.

During self-diagnostic check mode, the cruise control module checks for the following:
^ By moving cruise control switch to SET/COAST switch position, the cruise control module indicates the cruise control switch circuitry is in good condition by flashing the CRUISE indicator lamp two times every second.
^ By moving cruise control switch to the RES/ACC switch position, the cruise control module indicates the cruise control switch circuitry is in good condition by flashing the CRUISE indicator lamp three times every second.
^ With the vehicle's drive wheels raised, the cruise control module turns ON the CRUISE indicator lamp when it senses the wheels turning. However, whenever one of the cancel switches is closed (cruise control switch to CANCEL, manual selector lever in Park or Neutral, clutch pedal pressed, or brake pedal pressed), the cruise control module turns OFF the CRUISE indicator lamp for the duration of such switch closed. The cruise control module turns the CRUISE indicator lamp ON again as soon as such cancel switch opens.

When the Data Link Connector (DLC) terminal Tc is grounded (using a jumper between DLC terminals Tc and E1), the cruise control module will flash rapidly the CRUISE indicator (no DTCs stored in memory) or display any DTCs that are stored by flashing a numbered sequence. If more than one DTC is stored, they will be flashed sequentially from the lowest to the highest number.

TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic table.
3. This action commands the cruise control module to enter diagnostic mode.
4. Checks the cruise control switch in RES/ACC position.
5. Checks either CPP interrupt switch or the PNP switch.
6. Checks the stoplamp switch.
7. Checks the cruise control switch in CANCEL position.
9. Checks the PNP switch.
10. Checks the CPP interrupt switch.
11. Checks the VSS input circuit.
12. Checks the idle position switch of the TP sensor.
13. Checks for poor ground to the TP sensor.
14. Checks for an open in the idle switch signal circuit.
16. Checks for DTCs stored in cruise control module memory.
17. Checks for a faulty cruise control module causing to turn ON the CRUISE indicator lamp at all times.
18. Checks for a faulty cruise control module.
19. Checks for a short to ground in the idle switch signal circuit.
20. Checks for an open in the idle switch signal circuit.
24. Checks for an open in the diagnostic request signal circuit.
26. Checks the ability of the cruise control module to delay OD upshift when holding set speed under vehicle load.

DIAGNOSTIC AIDS
Check for the following:
^ Open ECU-IG Fuse.
^ Open ECU-B Fuse.
^ Open STOP Fuse.
^ Clean, tight G204.
^ Faulty cruise control module.
When the throttle is closed, the idle switch closes inside the Throttle Position (TP) sensor. The cruise control module uses the idle switch for accurate cruise control, thus maintaining set speed rapidly. If the idle switch is faulty (always open or closed), the engine's fuel injection system could be affected as well. Refer to Driveability and Emissions for a possible DTC P0120 set in the PCM memory.

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Inspect the harness connector for backed out terminals, improper mating, broken lock, improperly formed or damaged terminals and for poor terminal-to-wire connection before component replacement.

VEHICLES EQUIPPED WITH 4-SPEED AUTOMATIC TRANSAXLE:
When driving uphill with cruise control engaged, the transaxle may downshift from OD to 3rd gear, as deemed necessary by the Powertrain Control Module (PCM). When downshift occurs, the PCM signals the cruise control module of such action taking place by sending current through BRN/WHT wire.

In order to reduce "gear hunting," thus providing smoother driving, the cruise control module sends a signal (grounds RED wire) to the PCM to delay an upshift from 3rd gear to OD until the vehicle has reached the end of the slope.