P0870-OD HYDRAULIC PRESSURE TEST

For a complete wiring diagram Refer to Section 8W

Theory of Operation

The Transmission Control System tests the pressure switches when they are off. The test verifies that the switches are operational (They will close with pressure applied). The Transmission Control System verifies that the switch closes when the corresponding element is applied. If a switch fails to close, it is re-tested. If it fails the second test, the DTC will set, the MIL will illuminate and the transmission system will default to the orderly Shutdown routine.

When Monitored:
In any forward gear with engine speed above 1000 rpm shortly after a shift and every minute thereafter.
Set Condition:
After a shift into a forward gear, with engine speed above 1000 rpm, the PCM momentarily turns on element pressure to the Clutch circuits that don't have pressure to identify the correct Pressure Switch closes. If the Pressure Switch does not close 2 times, the DTC sets.

Possible Causes

LINE PRESSURE SENSOR

TRANSMISSION FLUID CONTAMINATION

RELATED DTCS PRESENT

TRANSMISSION SOLENOID/TRS ASSEMBLY

EXCESSIVE DEBRIS IN OIL PAN

POOR LINE PRESSURE SENSOR CONNECTION

TRANSMISSION CONTROL RELAY DTCS PRESENT

(F856) 5-VOLT SUPPLY CIRCUIT OPEN

TRANSMISSION CONTROL RELAY OUTPUT CIRCUIT OPEN

(F856) 5-VOLT SUPPLY CIRCUIT SHORT TO GROUND

(T9) OD PRESSURE SWITCH SENSE CIRCUIT SHORT TO OTHER CIRCUITS

TRANSMISSION SOLENOID/TRS ASSEMBLY

INTERNAL TRANSMISSION

POWERTRAIN CONTROL MODULE

Always perform the 45RFE/545RFE Pre-Diagnostic Troubleshooting Procedure before proceeding. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

Diagnostic Test

1. CHECK IF RELATED DTCS ARE PRESENT

With the scan tool, check DTCs.

Is there any Loss of Prime, TCM Power Input, Line Pressure Sensor and/or TIPM TCM Power Control Circuit DTCs present?

Yes

Refer to the Transmission category and perform the appropriate symptom. If the DTC, P0944-LOSS OF PRIME is present, perform its respective test first.

Go To 2

2. CHECK IF THE DTC P0760 IS PRESENT

With the scan tool, check DTCs.

Is the DTC P0760 also present?

Yes

Refer to the symptom list and perform diagnostics for P0760-OD SOLENOID CIRCUIT.

Go To 3

3. CHECK IF OTHER DTCS ARE PRESENT

With the scan tool, check DTCs.

Are any of the DTCs, P0733, P0734 ,P0735 and/or P0871 present also?

Yes

Go To 12

Go To 4

4. CHECK TO SEE IF DTC P0870 IS CURRENT

With the scan tool, check the STARTS SINCE SET counter for P0870.

Is the STARTS SINCE SET COUNTER 2 or less?

Yes

Go To 5

Go To 15

5. CHECK IF THE LINE PRESSURE STAYS THE SAME

Start the engine.
Warm the transmission to 82 degrees C (180 degrees F).
Firmly apply the brakes.
With the scan tool, monitor the Line Pressure during the following step.
Move the shift lever to each gear position, pausing momentarily in each position and record the line pressure reading. Allow the pressure to stabilize for at least 5 seconds in each range.

Did the line pressure remain at a steady value between 585 and 655 kPa (85 and 95 psi) in each position?

Yes

Go To 6

Go To 10

6. 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 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

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 7

7. CHECK THE LINE PRESSURE SENSOR OPERATION

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 while turning the Pressure Switch selector to each of the 3 line pressure positions on the Transmission Simulator.

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 scan tool Line Pressure readings match the specified readings on the Transmission Simulator and remain steady in all three positions?

Yes

Replace the Line Pressure Sensor per the Service Information.

Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

Go To 8

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

Turn the ignition off to the lock position.
Disconnect Transmission Simulator.
Disconnect the PCM C4 harness connector and connect Miller tool #8815.

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 (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 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

Go To 9

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

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 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

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 per the Service Information. With the scan tool, perform QUICK LEARN.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

10. COMPARE THE SCAN TOOL TO THE PRESSURE GAUGE

Turn the ignition off to the lock position.
Connect the Line Pressure Adapter, Miller tool #8259 and 0-300 psi Test Gauge, Miller tool #C-3293-SP. Refer to the Service Information for proper installation procedure.

CAUTION: Apply parking brake.

Start the engine.
In the following steps, compare the scan tool Line Pressure to the Pressure Gauge readings in each gear.

CAUTION: Do not overheat transmission.

With the gear selector in park, raise the rpm to 1500, and compare line pressure readings.
Firmly apply the brakes, move the gear selector into reverse, raise the rpm to 1500, and compare the line pressure readings.
Firmly apply the brakes, move the gear selector into drive, raise the rpm to 1500, and compare the line pressure readings.

Did the scan tool Line Pressure readings match the Pressure Gauge readings +/- 10 psi?

Yes

Go To 11

Replace the Line Pressure Sensor per the Service Information.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

11. CHECK THE WIRING AND CONNECTORS

Turn the ignition off to the lock position.
Remove the Line Pressure Adapter, Miller tool #8259 and 0-300 psi Test Gauge, Miller tool #C-3293-SP.
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.
On the Transmission Simulator, turn the Pressure Switch selector switch to OD.
Ignition on, engine not running.
With the scan tool, monitor the OD Pressure Switch state while pressing and holding the Pressure Switch test button and wiggling the wire harness and connectors that pertain to the OD Pressure Switch.

Did the OD Pressure Switch state change to closed and remain closed while wiggling the wires?

Yes

Go To 12

Go To 14

12. CHECK FOR EXCESSIVE DEBRIS

Turn the ignition off to the lock position.
Remove the Transmission Simulator, Miller tool #8333.
Remove and inspect the Transmission Oil Pan per the Service Information.

Does the Transmission Oil Pan contain excessive debris or contamination?

Yes

Repair the cause of the excessive debris in the Transmission Oil Pan. Refer to the Service Information for the proper procedures.

Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

Go To 13

13. CHECK THE OD HYDRAULIC CLUTCH CIRCUIT

Remove the Valve Body and air check the OD hydraulic clutch circuit (in the case) for leakage per the Service Information.

NOTE: The OD hydraulic clutch circuit contains a small bleed orifice which connects to the Reverse hydraulic clutch circuit. A small amount of air leakage is normal.

Was there excessive air leakage noticed during the air check?

Yes

Repair as necessary. Check the OD/Rev clutch piston seals, bleed orifice assembly, reaction shaft support seal rings, and machining of the main mating faces on the pump housing, pump valve body, and reaction shaft support.

Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

Disassemble and inspect the Valve Body and repair as necessary. Inspect the OD Accumulator piston and seals. Check for an extra check ball downstream from the #6 check ball pocket and repair as necessary. If no problems are found in the Valve Body, replace the Transmission Solenoid/TRS Assembly per the Service Information.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

14. CHECK THE (T9) OD PRESSURE SWITCH SENSE CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT

Disconnect all PCM harness connectors.
Disconnect the Transmission Solenoid/TRS Assembly harness connector.

NOTE: Make sure the Transmission Solenoid/TRS Assembly harness connector is disconnected.

NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance between the (T9) OD Pressure Switch Sense circuit and all other circuits in the Transmission Solenoid/TRS Assembly harness connector.

Is the resistance below 5.0 ohms between the (T9) OD Pressure Switch Sense circuit and any other circuit(s) in the Transmission Solenoid/TRS Assembly harness connector?

Yes

Repair the (T9) OD Pressure Switch Sense circuit for a short to another circuit(s).

Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

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 per the Service Information. With the scan tool, perform QUICK LEARN.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

15. 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.
If the DTC EVENT DATA shows the DTC P0870 set while the Line Pressure was significantly below the Desired Line Pressure reading, check for causes of low line pressure (low fluid level, broken or mis-installed primary oil filter or filter seal, sticking Main Regulator Valve in the Pump Valve Body etc.). If the data shows the DTC set while the Line Pressure reading was significantly higher than the Desired Line Pressure, check the Line Pressure Sensor and related wiring.

Where there any problems found?

Yes

Repair as necessary.

Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

Test Complete.