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P0870






P0870-OD HYDRAULIC PRESSURE TEST





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

Theory of Operation

Pressure switches are normally off or open (no pressure applied) and read high (+12 volts). When an element is applied, the corresponding pressure switch closes to ground (0 volts) or turns on. The controller tests the OD and 2/4 pressure switches when they are off (when the corresponding friction element is not applied) by briefly applying the OD and 2/4 elements which will cause the corresponding pressure switch to close. The test verifies that the switches are operational and that the switch will close when the corresponding element is applied. If a switch fails to respond, it is re-tested. The MIL illuminates and the transmission system defaults to limp-in mode.

- 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 greater than 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.





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

1. CHECKING FOR LOSS OF PRIME DTC
1. With the scan tool, read DTCs.

Is the DTC P0944 present also?

Yes

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

No

- Go To 2

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

Are any of the DTCs P0732, P0734 and/or P0846 present also?

Yes

- Replace the Transmission Solenoid/Pressure Switch Assembly.
- Perform 42RLE TRANSMISSION VERIFICATION TEST Transmission Verification Test

No

- Go To 3

3. 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 4

No

- Go To 9

4. 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 #8333 and the Electronic Transmission Adapter kit.
4. Ignition on, engine not running.
5. With the Transmission Simulator, turn the Pressure Switch selector switch to OD.
6. With the scan tool, monitor the UD Pressure Switch state while pressing the Pressure Switch Test button on the Transmission Simulator.
7. Wiggle the wires leading to the PCM while pressing and holding the Pressure Switch Test button.

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

Yes

- Disassemble and inspect the Valve Body and repair or replace as necessary. If no problems are found in the Valve Body, replace the Transmission Solenoid/Pressure Switch Assembly.
- Perform 42RLE TRANSMISSION VERIFICATION TEST Transmission Verification Test

No

- Go To 5

5. CHECK THE (T9) OD PRESSURE SIGNAL CIRCUIT FOR AN OPEN




1. Turn the ignition off to the lock position.
2. Disconnect the PCM C4 harness connector.
3. Disconnect the Transmission Solenoid/Pressure Switch Assembly harness connector.

NOTE: Check connectors - Clean/repair as necessary.

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 (T9) OD Pressure Signal circuit between the Transmission Solenoid/Pressure Switch Assembly harness connector and the appropriate terminal of Miller tool #8815.

Is the resistance above 5.0 ohms?

Yes

- Repair the (T9) OD Pressure Signal circuit for an open.
- Perform 42RLE TRANSMISSION VERIFICATION TEST Transmission Verification Test

No

- Go To 6

6. CHECK THE (T9) OD PRESSURE SIGNAL CIRCUIT FOR A SHORT TO GROUND




1. Measure the resistance between ground and the (T9) OD Pressure Signal circuit.

Is the resistance below 5.0 ohms?

Yes

- Repair the (T9) OD Pressure Signal circuit for a short to ground.
- Perform 42RLE TRANSMISSION VERIFICATION TEST Transmission Verification Test

No

- Go To 7

7. CHECK THE (T9) OD PRESSURE SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE




1. Ignition on, engine not running.
2. With the scan tool under TIPM, actuate the Transmission.
3. Measure the voltage of the (T9) OD Pressure Signal circuit.

Is the voltage above 0.5 volts?

Yes

- Repair the (T9) OD Pressure Signal circuit for a short to voltage.
- Perform 42RLE TRANSMISSION VERIFICATION TEST Transmission Verification Test

No

- Go To 8

8. CHECK THE (T16) TRANSMISSION CONTROL OUTPUT CIRCUIT FOR AN OPEN




1. With the scan tool under TIPM, actuate the Transmission.
2. Using a 12-volt test light connected to ground, check (T16) Transmission Control Output circuit in the Transmission Solenoid/Pressure Switch Assembly harness connector.

NOTE: The test light must illuminate brightly. Compare the brightness to that of a direct connection to the battery.

Does the test light illuminate brightly?

Yes

- 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. Quick Learn Procedure
- Perform 42RLE TRANSMISSION VERIFICATION TEST Transmission Verification Test

No

- Repair the (T16) Transmission Control Relay Output circuit for an open. If the fuse is open make sure to check for a short to ground.
- Perform 42RLE TRANSMISSION VERIFICATION TEST Transmission Verification Test

9. CHECK THE WIRING AND CONNECTORS
1. The conditions necessary to set the 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.

Were there any problems found?

Yes

- Repair as necessary.
- Perform 42RLE TRANSMISSION VERIFICATION TEST Transmission Verification Test

No

- Test Complete.

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