P1721 (CA) - Line Pressure Sensor Fault

Name of Code:
P1721 (CA) - Line Pressure Sensor Error

When Monitored:
Continuously with engine running.

Set Condition:
If the Line Pressure Sensor (LPS) voltage is below 0.2 volts or above 4.75 volts the code will be set.

Theory of Operation:
Line pressured is controlled by the TCM. It is measured by the LPS and regulation is achieved by changing the duty cycle of the Pressure Control Solenoid (PCS) (0% duty cycle = solenoid off max line pressure, 100% duty cycle = solenoid on min line pressure). This sensor is continuously checked for out of range voltage by the TCM.

Transmission Effects:
The MIL will illuminate. The Transmission system will default to open loop line pressure control resulting in a fixed PCS duty cycle. This duty cycle will change slightly depending on temperature and current gear.

Possible Causes:
- LPS signal circuit shorted to ground, shorted to voltage, or open.
- 5-volt supply circuit shorted to ground, shorted to voltage, or open.
- Open sensor ground.
- Line Pressure Sensor.