DTC Advanced Diagnostics: P177A
DTC P177A:Line Pressure Solenoid Valve A Or Line Pressure Switch Stuck OFF

General Description

Line pressure mode combination table
 
Normal line pressure mode
Low line pressure mode
Line pressure solenoid valve A
OFF
ON
Line pressure switch
OFF
ON
Line pressure condition
Normal
Low

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 to 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 detect 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
Execution
Continuous
Sequence
None
Duration
4 seconds or more
DTC Type
Two drive cycles, MIL off, A/T gear position indicator blinks
OBD Status
PASSED/FAILED/NOT COMPLETED (STILL TESTING)

Enable Conditions
Condition
Minimum
Maximum
Battery voltage
[BATTERY VOLTAGE]
11 V
–
No active DTCs set (prevents monitor from running)
P0122, P0123, P0222, P0223, P0716, P0717, P0718, P0721, P0722, P0723, P0746, P0747, P0751, P0752, P0756, P0757, P0761, P0762, P0776, P0777, P0796, P0797, P0842, P0843, P0847, P0848, P0872, P0873, P0877, P0878, P0962, P0963, P0966, P0967, P0970, P0971, P0973, P0974, P0976, P0977, P0979, P0980, P0989, P0990, P1658, P1659, P1683, P1684, P2101, P2118, P2122, P2123, P2127, P2128, P2135, P2138, P2176, P2714, P2720, P2721
[ ]: HDS Parameter

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

Possible Cause
NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
Line pressure solenoid valve A stuck off
Line pressure switch OPPLSW line open (includes connector loose connection or disconnection)
Line pressure switch OPPLSW line short to power
Line pressure switch stuck off
PCM internal circuit failure

Confirmation Procedure
Operating Condition
1.
Start the engine.
2.
Drive the vehicle in D until the transmission shifts into 6th gear.
Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.
With the HDS
None.

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, the A/T gear position indicator blinks and a Confirmed DTC and the freeze data are stored. The MIL does not come on.

Conditions for clearing the DTC
The A/T gear position indicator comes off by pressing the engine start/stop button to select the OFF mode. The Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command.