Cruise Control System Operation

The cruise control system is an integration of the cruise control module and PCM. Cruise control inputs from the cruise brake, cruise clutch (manual only), cruise on/off, cruise resume/accel, cruise set/coast and stop lamp switch go directly to the cruise control module. Vehicle speed is sent to the cruise control module from the PCM. The PCM creates a square wave vehicle speed signal by pulse width modulating circuit 817 to ground. The cruise control module monitors the voltage on circuit 817, which it pulls up to 5 volts through resistance. The lower the vehicle speed, the longer the pulse width modulated on-time (lower the voltage on circuit 817). The following list is the criteria that the cruise control module must detect before it will control vehicle speed:

• Must have an ignition voltage supply and ground.
• Must have ignition voltage at the cruise on/off switch input.
• Must have ignition voltage at the cruise brake switch input.
• Must have zero volts at the stop lamp switch input.
• Must have detected a set/coast switch transition from zero volts to ignition voltage and back to zero volts within 1.4 seconds when all conditions to enable cruise have been met.
• Must have zero volts at the cruise enable input when vehicle speed is over 32 km/h (20 mph) (PCM is allowing cruise to enable). The cruise control module must also see ignition voltage on the line when vehicle speed is under 32 km/h (20 mph). If the cruise control module does not detect this, it will NOT allow cruise for the entire ignition cycle.
• Must have a valid vehicle speed signal from the PCM at or over 39 km/h (24 mph).

In order for the cruise control module to allow cruise operation, it must also have an enable input from the PCM. When conditions have been met to allow cruise operation, the PCM will supply a ground to circuit 83, which will signal the cruise control module that the PCM has detected all of the correct enable criteria to allow cruise. This enable command can be viewed on the scan tool as CRUISE ENABLE. The cruise control module will not allow cruise operation until it sees zero volts on the cruise enable circuit. The following list is the criteria for the PCM to allow the cruise control module to control vehicle speed:

• Vehicle speed must be at or over 32 km/h (20 mph).
• Engine speed must be below the high RPM cutoff.
• Transaxle must be in a cruise gear (D4, D3 or D2 auto only).
• Clutch pedal must be fully released. Ignition voltage must be present at the brake/clutch switch input (manual only).
• The PCM must see one valid cruise clutch switch transition from ignition voltage to zero volts and back to ignition voltage once in the ignition cycle (manual only).
• The PCM must see one valid stop lamp switch transition from zero volts to battery voltage and back to zero volts once in the ignition cycle (auto only).
• Vehicle acceleration or deceleration rate must be within acceptable limits.
• Traction control must NOT be active.
• No PCM DTCs that would affect cruise operation can be set:
  • Engine coolant temperature circuit.
  • Engine coolant overtemperature.
  • PCM internal hardware.
  • Stop lamp switch circuit.
  • System voltage.
  • Transaxle range switch circuit.

Once the cruise control module receives correct voltage levels at the various inputs, it will engage cruise control and supply a ground to the cruise engage circuit 396. This lets the PCM know that the cruise control module is taking control of vehicle speed. CRUISE ENGAGED on scan tool will display YES when the cruise control module is taking control of vehicle speed.