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P0871






P0871-OD PRESSURE SWITCH RATIONALITY





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

Theory of Operation

The Transmission system uses three pressure switches to monitor the fluid pressure in the L/R, 2/4, and OD elements. The pressure switches are continuously monitored for the correct states in each gear. Normal operation will be experienced if no other codes are present. Transmission Control System will ignore the code. Limp-in condition will only occur if DTC P0871 is present with a DTC P0706.

- When Monitored:
Whenever the engine is running.

- Set Condition:
The DTC is set if one of the pressure switches are open or closed at the wrong time in a given gear. If the problem is identified for 3 successive key starts, the transmission will go into Limp-in mode and the MIL will turn on after 10 seconds of vehicle operation.





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

PRESSURE SWITCH STATES






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

Are there any TCM Power Input DTCs present?

Yes

- Perform the appropriate diagnostic procedure.

No

- Go To 2

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

Is the DTC P0944 present also?

Yes

- Perform the appropriate diagnostic procedure.

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 8

4. PCM AND WIRING
1. Turn the ignition off to the lock position.
2. Remove the Starter Relay.

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

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

NOTE: Removal of the Starter Relay is to prevent a Transmission, NO RESPONSE, condition and disable the starter.

3. Install the Transmission Simulator 8333 and the Electronic Transmission Adapter kit.
4. Ignition on, engine not running.
5. With the Transmission Simulator, turn the Pressure Switch selector to OD.
6. With the scan tool , monitor the OD Pressure Switch state while pressing the Pressure Switch Test button on the Transmission Simulator.

Did the OD Pressure Switch state change?

Yes

- Replace the Transmission Solenoid/Pressure Switch Assembly.
- Perform the 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.

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 the PCM Pinout Box 8815.

Is the resistance above 5.0 Ohms?

Yes

- Repair the (T9) OD Pressure Signal circuit for an open.
- Perform the 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. Remove the Transmission Control Relay.
2. Connect a jumper wire between the (A104) Fused B(+) circuit and (T16) Transmission Control Output circuit.
3. Ignition on, engine not running.
4. Measure the voltage of the (T9) OD Pressure Signal circuit.

Is the voltage above 0.5 of a volt?

Yes

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

8. 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 the 42RLE TRANSMISSION VERIFICATION TEST. Transmission Verification Test.

No

- Test Complete.

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