P0871-OD PRESSURE SWITCH RATIONALITY





For a complete wiring diagram Refer to Section 8W.

Theory of Operation


The Transmission system uses three pressure switches to monitor the fluid pressure in the LR, 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.



Possible Causes
RELATED TIPM TCM POWER INPUT DTCS PRESENT
LOSS OF PRIME DTC PRESENT
(T9) OD PRESSURE SWITCH SENSE CIRCUIT OPEN
(T9) OD PRESSURE SWITCH SENSE CIRCUIT SHORT TO GROUND
(T9) OD PRESSURE SWITCH SENSE CIRCUIT SHORT TO VOLTAGE
TRANSMISSION SOLENOID/PRESSURE SWITCH ASSEMBLY
POWERTRAIN CONTROL MODULE


Always perform the 42RLE Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)


PRESSURE SWITCH STATES

GEAR
L/R
2/4
OD
R
OPEN
OPEN
OPEN
P/N
CLOSED
OPEN
OPEN
1st
CLOSED
OPEN
OPEN
2nd
OPEN
CLOSED
OPEN
D
OPEN
OPEN
CLOSED
OD
OPEN
CLOSED
CLOSED



Diagnostic Test

1. CHECK FOR TIPM TCM POWER INPUT DTCS

With the scan tool under TIPM, check for TCM Power Input DTCs.

Are there any TIPM TCM Power Input DTCs present?

Yes


No

2. CHECK FOR LOSS OF PRIME DTC

With the scan tool, check for other Transmission DTCs.

Is the DTC P0944 present also?

Yes


No

3. CHECK TO SEE IF P0841 IS CURRENT

With the scan tool, view DTCs.

Is the status Active for this DTC or is the STARTS SINCE SET counter 2 or less?

Yes


No

4. PCM AND WIRING

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 and the Electronic Transmission Adapter kit.
Ignition on, engine not running.
With the Transmission Simulator, turn the Pressure Switch selector to OD.
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


No

5. (T9) OD PRESSURE SWITCH SENSE CIRCUIT OPEN



Turn the ignition off to the lock position.
Disconnect the PCM C4 harness connector.
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 Miller Tool #8815 to perform diagnosis.


Measure the resistance of the (T9) OD Pressure Switch Sense 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


No

6. (T9) OD PRESSURE SWITCH SENSE CIRCUIT SHORT TO GROUND



Measure the resistance between ground and the (T9) OD Pressure Switch Sense circuit.

Is the resistance below 5.0 ohms?

Yes


No

7. (T9) OD PRESSURE SWITCH SENSE CIRCUIT SHORT TO VOLTAGE



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

Is the voltage above 0.5 volts?

Yes


No

8. INTERMITTENT WIRING AND CONNECTORS

The conditions necessary to set the 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.

Were there any problems found?

Yes


No