68RFE Automatic Transmission
P0869-LINE PRESSURE HIGH
For a complete wiring diagram refer to Diagrams/Electrical. Electrical Diagrams
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 higher than the highest desired line pressure ever used in the current gear, the line pressure high DTC P0869 will set.
- When Monitored:
Continuously while driving in a forward gear.
- Set Condition:
The PCM continuously monitors Actual Line Pressure. If the Actual Line Pressure reading is greater than the maximum desired line pressure ever used in the current gear, while the Pressure Control Solenoid duty cycle is at or near its maximum value (which should result in minimum line pressure) for 3.5 seconds continuously, the DTC will set.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. 68RFE Pre-Diagnostic Troubleshooting Procedure
Diagnostic Test
1. CHECK FOR RELATED DTC'S
With the scan tool, check for other Transmission DTCs.
Is the DTC P0933 or P0882 present also?
Yes
- Refer to the Transmission category and perform the appropriate symptom.
No
- Go To 2
2. CHECK IF THE DTC IS CURRENT
With the scan tool, check the STARTS SINCE SET counter for P0869.
Is the STARTS SINCE SET COUNTER 2 or less?
Yes
- Go To 3
No
- Go To 10
3. CHECK THE LINE PRESSURE SENSOR CONNECTION
Ignition on, engine not running.
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 volts when the connector was pushed inward?
Yes (value was higher and changed to 207 kPa (30 psi) or 0.7 volts)
- Disconnect and properly reconnect the Line Pressure Sensor connector. Inspect terminals and repair as necessary.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
No (value is higher than 207 kPa (30 psi) or 0.7 volts and did not change or the value was already 207 kPa (30 psi) or 0.7 volts and did not change)
- Go To 4
4. CHECK THE PCM AND WIRING
Turn the ignition off to the lock position.
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 personal injury or death.
Install the Transmission Simulator, Miller tool #8333.
With the Transmission Simulator select the "OFF" position on the "Input/Output Speed" switch.
Ignition on, engine not running.
With the scan tool, monitor the Line Pressure during the following step.
Using the Transmission Simulator, set the rotary switch to each of the 3 line pressure positions.
NOTE: All three scan tool Line Pressure readings should be steady and ±14 kPa (2.0 psi) of the reading specified on the Transmission Simulator.
Did the Line Pressure read within ±14 kPa (2.0 psi) in all three positions?
Yes
- Go To 5
No
- Go To 6
5. CHECK THE LINE PRESSURE SENSOR CALIBRATION
Turn the ignition off to the lock position.
Disconnect the Transmission Simulator, Miller tool #8333 and reconnect all previously disconnected connectors.
Install the Line Pressure Adaptor, Miller tool #8259, and Pressure Gauge, Miller tool #C-3293, 0 to 2000 kPa (0 to 300 psi).
Start the engine in park.
Monitor the Line Pressure readings on the scan tool and the pressure gauge.
Compare the Line Pressure readings between the scan tool and the pressure gauge.
Is the pressure gauge reading within 34 kPa (5 psi) of the scan tool reading?
Yes
- Repair the internal transmission and inspect the Transmission Oil Pump and replace if necessary. If no problem is found, replace the Transmission Solenoid/TRS Assembly, possible cause is a stuck Pressure Control Solenoid.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
No
- Replace the Line Pressure Sensor.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
6. CHECK THE (T118) PRESSURE CONTROL SOLENOID CONTROL CIRCUIT FOR AN OPEN
Turn the ignition off to the lock position.
Disconnect the Transmission Simulator, Miller tool #8333.
Disconnect the Powertrain Control Module C4 harness connector.
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.
Measure the resistance of the (T118) Pressure Control Solenoid Control circuit between the Solenoid/TRS Assembly harness connector and the appropriate terminal of Miller tool #8815.
Is the resistance above 5.0 ohms?
Yes
- Repair the (T118) Pressure Control Solenoid Control circuit for an open.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
No
- Go To 7
7. CHECK THE (T118) PRESSURE CONTROL SOLENOID CONTROL CIRCUIT FOR A SHORT TO GROUND
Measure the resistance between ground and the (T118) Pressure Control Solenoid Control circuit.
Is the resistance below 5.0 ohms?
Yes
- Repair the (T118) Pressure Control Solenoid Control circuit for a short to ground.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
No
- Go To 8
8. CHECK THE (F856) 5-VOLT SUPPLY CIRCUIT FOR AN OPEN
Disconnect the Powertrain Control Module C1 harness connector.
Measure the resistance of the (F856) 5-volt Supply circuit between the Line Pressure Sensor harness connector and the appropriate terminal of Miller tool #8815.
Is the resistance above 5.0 ohms?
Yes
- Repair the (F856) 5-volt Supply circuit for an open.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
No
- Go To 9
9. CHECK THE (F856) 5-VOLT SUPPLY CIRCUIT FOR A SHORT TO GROUND
Disconnect the PCM C1 harness connector.
Disconnect the Line Pressure Sensor harness connector.
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.
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 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission 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 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
10. INTERMITTENT WIRING AND CONNECTORS
The conditions necessary to set this DTC are not present at this time.
Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
Wiggle the wires while checking for shorted and open circuits.
With the scan tool, check the DTC EVENT DATA to help identify the conditions in which the DTC was set.
Where there any problems found?
Yes
- Repair as necessary.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test
No
- Test Complete.