P0934-LINE PRESSURE SENSOR CIRCUIT LOW





For a complete wiring diagram Refer to Section 8W.

Theory of Operation


Line pressure is electronically controlled by the Transmission Control System and is measured by the Line Pressure Sensor (LPS). The desired line pressure is continuously being compared to the actual line pressure and is regulated by electronically changing the duty cycle of the Pressure Control Solenoid (PCS). (5% duty cycle = solenoid off = max line pressure, 62% duty cycle = solenoid on = min line pressure).

The Transmission Control System calculates the desired line pressure based on inputs from the transmission and engine. A calculated torque input to the transmission is used as the primary input of the desired line pressure calculation and is called Torque Based Line Pressure. In addition, the line pressure is set to a preset level 827 to 931 kPa (120 to 135 PSI) during shifts and in Park and Neutral to ensure consistent shift quality.

The monitored Line Pressure Sensor voltage should always be between 0.35 and 4.75 volts. Any monitored voltages outside these parameters indicate a Line Pressure Sensor or wiring problem and will cause either DTC P0934 or P0935 to set.


  • When Monitored:

    Continuously with the ignition on and engine running.

  • Set Condition:

    This DTC will set when the monitored Line Pressure Sensor voltage is less than or equal to 0.35 volts for 0.18 seconds.


Possible Causes
  
(F856) 5-VOLT SUPPLY CIRCUIT OPEN
  
(F856) 5-VOLT SUPPLY CIRCUIT SHORT TO GROUND
  
(T38) LINE PRESSURE SENSOR SIGNAL CIRCUIT SHORT TO GROUND
  
LINE PRESSURE SENSOR
  
POWERTRAIN CONTROL MODULE
  

Always perform the 42RLE Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)



Diagnostic Test

1.CHECK IF DTC IS CURRENT


NOTE: This counter only applies to the last DTC set.



Is the STARTS SINCE SET counter 2 or less?

Yes
  • Go To 2


No
  • Go To 6

2.CHECK THE PCM AND WIRING



CAUTION: Removal of the Starter Relay will prevent the vehicle from being started in gear.


WARNING: The Starter Relay must be removed from the PDC. Failure to do so can result in personal injury or death.


NOTE: Removal of the Starter Relay is to prevent a Transmission, NO RESPONSE, condition and disable the starter.






NOTE: All three scan tool Line Pressure readings should be steady and ± 14 kPa or 2.0 psi of the reading specified on the Transmission Simulator.



Did the Line Pressure read within ± 14 kPa or 2.0 psi in all three positions?

Yes


No
  • Go To 3

3.CHECK THE (T38) LINE PRESSURE SENSOR SIGNAL CIRCUIT FOR A SHORT TO GROUND






CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller tool #8815 to perform diagnosis.




Is the resistance below 5.0 ohms?

Yes


No
  • Go To 4

4.CHECK THE (F856) 5-VOLT SUPPLY CIRCUIT FOR AN OPEN






Is the resistance below 5.0 ohms?

Yes
  • Go To 5


No

5.CHECK THE (F856) 5-VOLT SUPPLY CIRCUIT FOR A SHORT TO GROUND






Is the resistance below 5.0 ohms?

Yes


No
  • Using the schematics as a guide, check the Powertrain Control Module (PCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace and program the PCM per the Service Information. With the scan tool, perform QUICK LEARN.
  • Perform 42RLE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)

6.INTERMITTENT WIRING AND CONNECTORS






Where there any problems found?

Yes


No
  • Test Complete.