P0871

P0871-OD PRESSURE SWITCH RATIONALITY

Special Tools:










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

Theory of Operation

The Transmission Control 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. If the Transmission Control System detects an invalid OD pressure switch state, normal operation will continue if no other codes are present. Transmission Control System will ignore the invalid OD pressure switch state. 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 the OD pressure switch is open or closed at the wrong time in a given gear. If the P0706 fault condition is also present, the transmission will go into Limp-in mode and the MIL will turn on.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

PRESSURE SWITCH STATES






1. CHECK IF RELATED TCM DTCS ARE PRESENT
1. With the scan tool, read DTCs

Are there any TCM Power Input DTCs present also?

Yes

- Testing and Inspection Perform the appropriate transmission 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

- Testing and Inspection Perform the appropriate transmission diagnostic procedure.

No

- Go To 3

3. CHECK IF P0871 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. CHECK THE PCM AND WIRING WITH THE TRANSMISSION SIMULATOR
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: Failure to remove the Starter Relay can cause a Transmission - No Response condition.

3. Install the Transmission Simulator 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/TRS Assembly. Transmission Solenoid And Pressure Switch Assembly - Removal.
- Perform the 62TE TRANSMISSION VERIFICATION TEST. 62TE 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 C1 harness connector.
3. Disconnect the Transmission Solenoid/TRS Assembly harness connector.
4. Measure the resistance of the (T9) OD Pressure Signal circuit between the appropriate terminal of the PCM C1 harness connector and the Transmission Solenoid/TRS Assembly harness connector.

Is the resistance above 5.0 Ohms?

Yes

- Repair the (T9) OD Pressure Signal circuit for an open.
- Perform the 62TE TRANSMISSION VERIFICATION TEST. 62TE 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 the 62TE TRANSMISSION VERIFICATION TEST. 62TE Transmission Verification Test.

No

- Go To 7

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




1. Remove the PCM/TCM relay and with a fused jumper wire, jumper the Transmission Control Output to B(+).
2. Ignition on, engine not running.
3. 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 62TE TRANSMISSION VERIFICATION TEST. 62TE 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. Service and Repair. With the scan tool, perform Quick Learn.
- Perform the 62TE TRANSMISSION VERIFICATION TEST. 62TE 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 62TE TRANSMISSION VERIFICATION TEST. 62TE Transmission Verification Test.

No

- Test Complete.