P171A

Advanced Diagnostics - DTC P177A: Line Pressure Solenoid Valve A Stuck OFF, or Line Pressure Switch Stuck OFF










General Description
Line pressure solenoid valve A is installed on the transmission housing. It is controlled by the ON/OFF signal from the powertrain control module (PCM) to regulate line pressure to low line pressure or normal line pressure. The line pressure switch is installed in the hydraulic pressure output circuit from line pressure solenoid valve A. When line pressure solenoid valve A outputs hydraulic pressure, the line pressure is regulated to low line pressure and the switch is turned on. When line pressure solenoid valve A does not output hydraulic pressure, the line pressure is at normal line pressure and the switch is turned off. The signal from the line pressure switch is input to the PCM. The PCM detects the hydraulic pressure supply condition from line pressure solenoid valve A to detects a malfunction in line pressure solenoid valve A. If the line pressure switch is off against the command to turn on line pressure solenoid valve A, the PCM detects a line pressure solenoid valve A stuck off or line pressure switch stuck off failure and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type, OBD Status






Enable Conditions






Malfunction Threshold
The input signal from the line pressure switch to the PCM is high when the low line pressure mode is commanded.

Driving Pattern
1. Start the engine.
2. Drive the vehicle until the transmission shifts into 6th gear.

- Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.

Diagnosis Details

Conditions for setting the DTC
When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, a Confirmed DTC and the freeze data are stored. The MIL does not come on.

Conditions for clearing the DTC
The Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command or by disconnecting the battery.