P0869

P0869-LINE PRESSURE HIGH







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 827 or 931 kPa (120 or 135 psi) during shifts and in Park and Neutral to ensure consistent shift quality. The desired line pressure is continuously being compared to the actual 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 highest 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), the DTC will set.





Always perform the 42RLE Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview

1. CHECK FOR RELATED DTCS
1. With the scan tool, read DTCs.

Are there any line pressure sensor or transmission relay output DTCs present also?

Yes

- Refer to DTC Based Diagnostics and perform the appropriate diagnostic procedure.

No

- Go To 2

2. 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 3

No

- Go To 9

3. CHECK THE PCM AND WIRING USING THE TRANSMISSION SIMULATOR
1. Turn the ignition off to the lock position.
2. Remove the Starter Solenoid Relay from the TIPM.

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

WARNING: The Starter Solenoid Relay must be removed from the TIPM. Failure to do so can result in possible serious or fatal injury.

3. Install the Transmission Simulator, Miller tool #8333A and the Electronic Transmission Adapter kit.
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 step.
7. 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 or 2.0 psi (0.2 volts) of the reading specified on the Transmission Simulator.

Did the Line Pressure read within ± 14 kPa or 2.0 psi (0.2 volts) in all three positions?

Yes

- Go To 4

No

- Go To 5

4. CHECK THE LINE PRESSURE SENSOR CALIBRATION
1. Turn the ignition off to the lock position.
2. Disconnect the Transmission Simulator, Miller tool #8333A and the Electronic Transmission Adapter kit and reconnect all previously disconnected connectors.
3. Install the Line Pressure Gauge, Miller tool #C-3293, 0 to 2000 kPa or 0 to 300 psi in the L/R pressure port.
4. Start the engine in Park.
5. Monitor the Line Pressure readings on the scan tool and the pressure gauge.
6. Compare the Line Pressure readings between the scan tool and the pressure gauge.

Is the pressure gauge reading within 34 kPa or 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 Pressure Control Solenoid.
- Perform 42RLE TRANSMISSION VERIFICATION TEST 42RLE Transmission Verification Test

No

- Replace the Line Pressure Sensor.
- Perform 42RLE TRANSMISSION VERIFICATION TEST 42RLE Transmission Verification Test

5. CHECK THE (T118) LP VFS CONTROL CIRCUIT FOR AN OPEN




1. Turn the ignition off to the lock position.
2. Disconnect the Transmission Simulator, Miller tool #8333A.
3. 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 the PCM Pinout Box 8815 to perform diagnosis.

4. Measure the resistance of the (T118) LP VFS Control circuit between the Line Pressure Sensor/Variable Force Solenoid Assembly harness connector and the appropriate terminal of Miller tool #8815.

Is the resistance above 5.0 ohms?

Yes

- Repair the (T118) LP VFS Control circuit for an open.
- Perform 42RLE TRANSMISSION VERIFICATION TEST 42RLE Transmission Verification Test

No

- Go To 6

6. CHECK THE (T118) LP VFS CONTROL CIRCUIT FOR A SHORT TO GROUND




1. Measure the resistance between ground and the (T118) LP VFS Control circuit.

Is the resistance below 5.0 ohms?

Yes

- Repair the (T118) LP VFS Control circuit for a short to ground.
- Perform 42RLE TRANSMISSION VERIFICATION TEST 42RLE Transmission Verification Test

No

- Go To 7

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




1. Disconnect the PCM C1 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 the PCM Pinout Box 8815 to perform diagnosis.

2. Measure the resistance of the (F856) 5-volt Supply circuit between the Line Pressure Sensor/Variable Force Solenoid Assembly 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 42RLE TRANSMISSION VERIFICATION TEST 42RLE Transmission Verification Test

No

- Go To 8

8. 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 42RLE TRANSMISSION VERIFICATION TEST 42RLE 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 and program the PCM. With the scan tool, perform Quick Learn.
- Perform 42RLE TRANSMISSION VERIFICATION TEST 42RLE Transmission Verification Test

9. 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 42RLE TRANSMISSION VERIFICATION TEST 42RLE Transmission Verification Test

No

- Test Complete.