P0868

P0868-LINE PRESSURE LOW

Special Tools:










For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

Line pressure is measured by the Line Pressure Sensor (LPS) and regulation is achieved by changing the duty cycle of the Pressure Control Solenoid (PCS) controlled by the Transmission Control System. (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 both the engine and transmission.

The Transmission Control System calculates torque input to the transmission and uses it as the primary input to the desired line pressure calculation. This is called Torque Based Line Pressure. In addition, the line pressure is set to a preset level 1034 or 1103 kPa (150 or 160 psi) during shifts to ensure consistent shift quality. The actual line pressure is continuously being compared to the desired (target) line pressure. If the actual line pressure is consistently lower than the target while driving, the line pressure low DTC P0868 will set.

- When Monitored:
Continuously while driving in a forward gear.

- Set Condition:
The PCM continuously monitors Actual Line Pressure and compares it to Desired Line Pressure. If the Actual Line Pressure is more than 15 psi below Desired Line Pressure for 3.5 seconds continuously, this DTC will set.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. CHECK FOR RELATED DTCs
1. With the scan tool, read and record all DTCs.

Is the DTC P0933 present also?

Yes

- Testing and Inspection Perform the appropriate test.

No

- Go To 2

2. CHECK THE Event Data
1. With the scan tool, read the DTC Event Data for the DTC P0868.

Does the Line Pressure reading in the DTC Event Data show zero (0) psi?

Yes

- Go To 3

No

- Go To 4

3. VERIFY PROPER LINE PRESSURE
1. With the scan tool, erase all DTCs.
2. Start the vehicle in Park and raise engine speed to 1500 rpm.
3. With the scan tool, compare the Line Pressure and Desired Line Pressure.

Does the Line Pressure reading match the Desired Line Pressure reading (± 34.5 kPa or 5 psi)?

Yes

- Disregard this DTC P0868. Testing and Inspection Follow the diagnostic procedure for any other DTCs which are present.

No

- Go To 4

4. CHECK IF THE DTC IS CURRENT
1. With the scan tool, read DTCs.

Is the status Active or is the Starts Since Set counter 2 or less for this DTC?

Yes

- Go To 5

No

- Go To 15

5. CHECK THE LINE PRESSURE SENSOR CONNECTION
1. Ignition on, engine not running.
2. With the scan tool, monitor the Line Pressure while firmly pushing the Transmission Line Pressure Sensor connector inwards towards the Transmission.

Did the Line Pressure reading on the scan tool CHANGE to about 207 kPa (30 psi) or 0.7 of a volt when the connector was pushed inward?

Yes (value was higher and changed to 207 kPa (30 psi) or 0.7 of a volt)

- Disconnect and properly reconnect the Line Pressure Sensor connector. Inspect terminals and repair as necessary.
- Perform the 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Verification Test

No (value is higher than 207 kPa (30 psi) or 0.7 of a volt and did not change or the value was already 207 kPa (30 psi) or 0.7 of a volt and did not change)

- Go To 6

6. CHECK THE PCM AND WIRING USING THE TRANSMISSION SIMULATOR
1. Turn the ignition off to the lock position.
2. Remove the Ignition Switch Feed fuse from the TIPM.

CAUTION: Removal of the Ignition Switch Feed fuse from the TIPM will prevent the vehicle from being started in gear.

WARNING: The Ignition Switch Feed fuse must be removed from the TIPM. Failure to do so can result in possible serious or fatal injury.

3. Install the Transmission Simulator.
4. With the Transmission Simulator select the "OFF" position on the "Input/Output Speed" switch.
5. Ignition on, engine not running.
6. With the scan tool, monitor the Line Pressure during the following steps.
7. Using the Transmission Simulator, set the rotary knob to each of the three line pressure positions.

NOTE: All three scan tool Line Pressure readings should be steady and ± 14 kPa (2.0 psi) or 0.1 of a volt of the reading specified on the Transmission Simulator.

Did the Line Pressure read within ± 14 kPa (2.0 psi) or 0.1 of a volt in all three positions?

Yes

- Go To 7

No

- Go To 11

7. CHECK THE LINE PRESSURE SENSOR
1. Turn the ignition off to the lock position.
2. Disconnect the Transmission Simulator and reconnect all previously disconnected connectors.
3. Install the Line Pressure Adaptor , and the Pressure Gauge , 0 to 2000 kPa (0 to 300 psi).
4. Start the engine in park.
5. Monitor the line pressure readings of both the scan tool and the pressure gauge and compare the two readings.

Is the line pressure gauge reading within 34 kPa (5 psi) of the scan tool reading?

Yes

- Go To 8

No

- Replace the Line Pressure Sensor.
- Perform the 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Verification Test

8. CHECK FOR PROPER LINE PRESSURE
1. With the vehicle still in Park, raise the engine speed to 1500 rpm.
2. Compare line pressure readings of both the scan tool and the pressure gauge to the Desired Line Pressure reading on the scan tool.

Is the Line Pressure gauge and scan tool reading within 34 kPa (5 psi) of the Desired Line Pressure scan tool reading?

Yes

- Go To 15

No

- Go To 9

9. CHECK THE DEFAULT LINE PRESSURE
1. Turn the ignition off to the lock position.
2. Disconnect the Transmission Solenoid/TRS Assembly harness connector.

NOTE: Disconnection of the Transmission Solenoid/TRS Assembly harness connector may set several DTCs in the following steps. Disregard and erase any DTCs that set due to the disconnection.

3. Start the engine.
4. With the vehicle still in Park, raise the engine speed to 1500 rpm while monitoring the line pressure on the pressure gauge and record your findings.

Was the gauge reading greater than 130 psi?

Yes

- Go To 14

No

- Go To 10

10. CHECK FOR A PLUGGED TRANSMISSION OIL FILTER
1. Turn the ignition off to the lock position.
2. Remove and inspect the Transmission Oil Pan for excessive debris.
3. Remove and inspect the Primary Oil Filter.

NOTE: Make sure the Primary Transmission Oil Filter and/or O-ring is not cracked or split.

Does the Oil Pan contain excessive debris and/or is the Primary Oil Filter cracked or plugged?

Yes

- Repair the plugged, cracked, or split Primary Transmission Oil Filter and/or O-ring. If the Primary Transmission Oil Filter is plugged refer to the Service Information for the proper Hydraulic repair procedure.
- Perform the 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Verification Test

No

- Repair internal transmission and inspect the Transmission Oil Pump and replace if necessary. If no problem is found, replace the Solenoid/TRS Assembly.
- Perform the 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Verification Test

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




1. Disconnect the Transmission Simulator.
2. Reconnect all previously disconnected connectors except the Line Pressure Sensor harness connector.
3. Ignition on, engine not running.
4. Measure the voltage of the (F856) 5-volt Supply circuit in the Line Pressure Sensor harness connector.

Is the voltage above 5.5 volts?

Yes

- Repair the (F856) 5-volt Supply circuit for a short to voltage.
- Perform the 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Verification Test

No

- Go To 12

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




1. Turn the ignition off to the lock position.
2. Disconnect the PCM C2 harness connector.
3. Measure the resistance of the (F856) 5-volt Supply circuit between the Line Pressure Sensor harness connector and the appropriate terminal of the PCM C2 harness connector.

Is the resistance above 5.0 Ohms?

Yes

- Repair the (F856) 5-volt Supply circuit for an open.
- Perform the 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Verification Test

No

- Go To 13

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




1. Measure the resistance between ground and the (F856) 5-volt Supply circuit.

Is the resistance below 5.0 Ohms?

Yes

- Repair the (F856) 5-volt Supply circuit for a short to ground.
- Perform the 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Verification Test

No

- Go To 14

14. CHECK THE (T118) PRESSURE CONTROL SOLENOID CONTROL CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT




1. Turn the ignition off to the lock position.
2. Disconnect the Transmission Solenoid/TRS Assembly harness connector.
3. Disconnect all PCM harness connectors.
4. Measure the resistance between the (T118) Pressure Control Solenoid Control circuit and all other circuits in the Transmission Solenoid/TRS Assembly harness connector.

Is the resistance below 5.0 Ohms between the (T118) Pressure Control Solenoid Control circuit and any other circuit(s) in the Transmission Solenoid/TRS Assembly harness connector?

Yes

- Repair the (T118) Pressure Control Solenoid Control circuit for a short to another circuit(s).
- Perform the 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Verification Test

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 the PCM. With the scan tool, perform Quick Learn.
- Perform the 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Verification Test

15. CHECK THE WIRING AND CONNECTORS
1. The conditions necessary to set this DTC are not present at this time.
2. Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
3. Wiggle the wires while checking for shorted and open circuits.
4. With the scan tool, check the Event Data to help identify the conditions in which the DTC was set.

Where there any problems found?

Yes

- Repair as necessary.
- Perform the 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Verification Test

No

- Test Complete.