DTC 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
| Execution | Continuous |
| Sequence | None |
| Duration | 4 seconds or more |
| DTC Type | Two drive cycles, MIL off, A/T gear position indicator blinks |
Enable Conditions
| Condition | Minimum | Maximum | |
|---|---|---|---|
| 12 volt battery voltage [BATTERY VOLTAGE] | 11 V | - | |
[ ]: 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 a loose or disconnected connector)
- 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, 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 12 volt battery.