Powertrain Controls - ECM/PCM

Code 68:

Cruise Circuit:

CIRCUIT DESCRIPTION:

The PCM controlled cruise control system is designed to monitor itself to be sure that the desired cruise position and actual cruise position are equal to each other.

Code 68 sets when:

^ Actual SPS position is greater than 12% above desired SPS position of 0%.
^ The above condition is met for 1.5 seconds.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. Most VAC solenoids leak a small amount of vacuum when closed. But they should not leak enough to allow the servo to reach wide open throttle in 15.0 seconds with the vent closed.

2. When the VAC solenoid is forced "ON" the vacuum will be vented to atmosphere unless the vent valve is stuck closed.

DIAGNOSTIC AIDS:

Outside interference such as a CB antenna lead near the PCM wiring harness may cause a false SPS reading and set a false code 68. An intermittent may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation.

Check:

^ Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.