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P0846






P0846-2C PRESSURE SWITCH RATIONALITY





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

Theory of Operation

The Transmission system uses five pressure switches to monitor the fluid pressure in the L/R, 2C, 4C, UD, and OD clutch circuits. The pressure switches are continuously monitored for the correct states in each gear as shown.

- When Monitored:
Continuously with the ignition on, engine running, with the transmission in gear.

- Set Condition:
The DTC is set if the 2C Pressure Switch reads open or closed at the wrong time in a given gear.





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






1. DETERMINING IF RELATED RELAY DTCS ARE PRESENT
1. With the scan tool, check for other transmission DTCs.

Are there any TCM Power Input DTCs present?

Yes

- Testing and Inspection Perform the appropriate diagnostic procedure.

No

- Go To 2

2. DTC DATA SHOW CURRENT DTC
1. With the scan tool, check the Event Data.

Does the Event Data show data for DTC P0846?

Yes

- Go To 3

No

- Testing and Inspection Perform the appropriate test shown in the Event Data.

3. MULTIPLE DTCS PRESENT
1. With the scan tool, check for other transmission DTCs.

Are there two or more related pressure switch rationality DTCs present in addition to P0846?

Yes

- Go To 4

No

- Go To 7

4. RELATED DTC PRESENT
1. With the scan tool, check the Event Data for P0846.

NOTE: Make sure to record all Event Data stored in the scan tool for future reference in this test procedure.

Do all the pressure switches read CLOSED in the Event Data for P0846?

Yes

- P0882 Perform diagnostics for P0882.

No

- Go To 5

5. Event Data READ OPEN
1. In the Event Data recorded earlier, read the state of all pressure switches.

Do all the pressure switches read OPEN?

Yes

- Go To 6

No

- Go To 7

6. LOW LINE PRESSURE
1. In the Event Data recorded earlier, compare the Line Pressure and the Desired Line Pressure.

Is the Line Pressure less than 40 psi, and significantly below the Desired Line Pressure?

Yes

- Repair as necessary to correct low line pressure. Check fluid level and adjust as necessary. If fluid level is OK, check the Primary Oil Filter seal for a split, crack, or improperly installed. If the filter and seal are OK, check the Main Regulator Valve in the Oil Pump. Refer to the Service Information for the above procedures.
- Perform the 545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test.

No

- Replace the Transmission Solenoid/TRS Assembly.
- Perform the 545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

7. EVENT DATA READS DTC SET IN PARK REVERSE OR NEUTRAL
1. With the scan tool, check the Event Data for P0846.

NOTE: Make sure to record all Event Data stored in the scan tool for future reference in this test procedure.

Does the Event Data show the DTC P0846 set in Park, Neutral, or Reverse?

Yes

- Go To 12

No

- Go To 8

8. EVENT DATA READS 2C PRESSURE SWITCH READING CLOSED
1. With the scan tool, check the Event Data for P0846.

NOTE: Make sure to record all Event Data stored in the scan tool for future reference in this test procedure.

Does the Event Data show the 2C Pressure Switch reading CLOSED?

Yes

- Go To 10

No

- Go To 9

9. PRIMARY OIL FILTER SEAL
1. In the Event Data recorded earlier, compare the Line Pressure and the Desired Line Pressure.

Is the Line Pressure less than 40 psi, and significantly below the Desired Line Pressure?

Yes

- Repair as necessary to correct low line pressure. Check fluid level and adjust as necessary. If fluid level is OK, check the Primary Oil Filter seal for a split, crack, or improperly installed. If the filter and seal are OK, check the Main Regulator Valve in the Oil Pump. Refer to the Service Information for the above procedures.
- Perform the 545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Go To 15

10. 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: Failure to remove the Starter Relay can cause a Transmission - No Response condition.

3. Install the Transmission Simulator 8333.
4. Ignition on, engine not running.
5. With the Transmission Simulator, turn the Pressure Switch selector switch to the 2C position.
6. With the scan tool, monitor the 2C Pressure Switch while pressing the Pressure Switch test button on the Transmission Simulator.

Did the state of the 2C Pressure Switch change while pressing the Pressure Switch Test button?

Yes

- Go To 11

No

- Go To 12

11. TRANSMISSION SOLENOID/TRS ASSEMBLY
1. Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
2. Wiggle the wires while checking for shorted and open circuits.

Where there any problems found?

Yes

- Repair as necessary.
- Perform the 545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Replace the Transmission Solenoid/TRS Assembly.
- Perform the 545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

12. (T147) 2C PRESSURE SWITCH SENSE CIRCUIT OPEN




1. Turn the ignition off to the lock position.
2. Disconnect the Transmission Simulator 8333.
3. Disconnect the PCM C4 harness connector.
4. Connect the PCM Pinout Box 8815 to the PCM C4 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.

5. Measure the resistance of the (T147) 2C Pressure Switch Sense circuit between the Transmission Solenoid/TRS Assembly harness connector and the appropriate terminal of the PCM Pinout Box 8815.

Is the resistance above 5.0 Ohms?

Yes

- Repair the (T147) 2C Pressure Switch Sense circuit for an open.
- Perform he the 545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Go To 13

13. (T147) 2C PRESSURE SWITCH SENSE CIRCUIT SHORTED TO GROUND




1. Measure the resistance between ground and the (T147) 2C Pressure Switch Sense circuit.

Is the resistance below 5.0 Ohms?

Yes

- Repair the (T147) 2C Pressure Switch Sense circuit for a short to ground.
- Perform the 545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Go To 14

14. (T147) 2C PRESSURE SWITCH SENSE CIRCUIT SHORTED TO ANOTHER CIRCUIT




1. Measure the resistance between the (T147) 2C Pressure Switch Sense circuit and all the other circuits in the Transmission Solenoid/TRS Assembly harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Repair the (T147) 2C Pressure Switch Sense circuit for a short to another circuit(s).
- Perform the 545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Replace the Powertrain Control Module. With the scan tool, perform the Quick Learn procedure. Quick Learn Procedure
- Perform the 545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

15. #5 AND/OR #7 CHECK BALL CUT OR DAMAGED
1. Turn the Ignition off to the lock position.
2. Remove the Valve Body Assembly.
3. Inspect the #5 and #7 check balls for any cuts or damage. Check for an extra check ball in the passage downstream from the #7 check ball pocket.
4. Inspect the 2C accumulator piston and seals and also the 2C tower seal on top of the valve body. Refer to the Service Information.

Where there any problems found?

Yes

- Repair as necessary. Check for excessive clutch debris in the transmission oil pan. If excessive clutch debris is present, repair 2C clutch as necessary. Refer to the Service Information for proper repair procedures.
- Perform the 545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Go To 16

16. EXCESSIVE FLUID LEAKAGE WITH 2C CLUTCH CIRCUIT
1. Air check the 2C Clutch hydraulic circuit. Refer to the Service Information.

NOTE: This hydraulic clutch circuit contains a small bleed orifice. Small leakage is considered normal.

Was there excessive air leakage in the 2C Clutch hydraulic circuit?

Yes

- Repair as necessary. Refer to the Service Information.
- Perform the 545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Replace the Transmission Solenoid/TRS Assembly.
- Perform the 545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

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