Cruise Control System Diagnosis

Diagnosis
The following table will diagnose the cruise disable and cruise engaged circuits. Refer to Wiring Repairs when diagnosing the remaining Cruise Control System circuits.

Circuit Description
The stepper motor cruise module communicates with the Powertrain Control Module (PCM) over three circuits (cruise engaged, cruise disabled and VSS output). The cruise enable status tells the PCM if the cruise control system is enabled. The vehicle speed sensor (VSS) output is the speed signal from the vehicle speed sensor through the PCM and used by the cruise control module. The cruise disable line allows the PCM to disable cruise under the various conditions described below:
^ DTCs P0122, P0123, P0200, P0335, P0502, P0562, P0563 not set.
^ Engine is not running.
^ Transmission is in park, neutral, or reverse (automatic transmission).
^ Transmission is out of gear (manual transmission).
^ Safety fuel cut-off is active.
If the PCM detects any one of the above conditions, it will interrupt the ground at the cruise disable input circuit and disable the cruise control.

Diagnostic Aids
^ This table will not diagnose any cruise control system circuits other than those connected to the PCM. For diagnosis of the remaining circuits, refer to Wiring Repairs in Diagrams.
^ An Intermittent problem may be caused by:
^ A poor connection
^ Rubbed through wire insulation
^ A wire that is broken inside the insulation
^ The cruise control system may disable if actual speed is less than 24 km/h (15 mph) than commanded vehicle speed, i.e. towing a trailer, or climbing a steep grade.
^ Minimum vehicle speed for setting the cruise control system is 40 km/h (25 mph).

Test Description
The number(s) below refer(s) to the step number(s) on the Diagnostic Table.
1. The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the malfunction occurred. The scan tool stores this data for later reference.
2. The cruise speed set has to be above the minimum speed (25 mph/40 km/h) required for cruise operation. Drive vehicle in an area where enough room is allowed for cruising.
6. Even though the cruise module can maintain the set speed, the cruise control module may not tell the PCM that it is controlling vehicle speed. This step determines if the malfunction is an open cruise engaged circuit or a malfunctioning cruise control module.
18. Reprogram the replacement PCM and perform the Crankshaft Position system variation learning procedure. Refer to the latest Techline information for PCM programming and the CKP System Variation Learn Procedure for the Crankshaft Position system variation learning procedure.
19. If no malfunctions have been found at this point and no additional DTCs were set, refer to Diagnostic Aids for additional checks and information.