P0846-2C PRESSURE SWITCH RATIONALITY

For a complete wiring diagram Refer to Section 8W

Theory of Operation

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

Possible Causes

RELATED TCM POWER INPUT DTCS PRESENT

(T147) 2C PRESSURE SWITCH SENSE CIRCUIT OPEN

(T147) 2C PRESSURE SWITCH SENSE CIRCUIT SHORT TO GROUND

(T147) 2C PRESSURE SWITCH SENSE CIRCUIT SHORT TO OTHER CIRCUITS

EXCESSIVE FLUID LEAKAGE IN 2C CLUTCH CIRCUIT

NO. 5 AND/OR NO. 7 CHECK BALL CUT OR DAMAGED

EXTRA CHECK BALL DOWNSTREAM OF THE NO. 7 CHECK BALL SOCKET

LOW LINE PRESSURE

TRANSMISSION SOLENOID/TRS ASSEMBLY

POWERTRAIN CONTROL MODULE

WIRING AND CONNECTORS

Always perform the 45RFE/545RFE Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

GEAR	L/R	2C	4C	UD	OD
REVERSE	OPEN	OPEN	OPEN	OPEN	OPEN
P/N	CLOSED**	OPEN	OPEN	OPEN	OPEN
1ST	CLOSED*	OPEN	OPEN	CLOSED	OPEN
2ND	OPEN	CLOSED	OPEN	CLOSED	OPEN
2ND PRIME	OPEN	OPEN	CLOSED	CLOSED	OPEN
3RD	OPEN	OPEN	OPEN	CLOSED	CLOSED
4TH	OPEN	OPEN	CLOSED	OPEN	CLOSED
5TH	OPEN	CLOSED	OPEN	OPEN	CLOSED
*L/R is closed if output speed is below 100 rpm in Drive and Manual 2. L/R is closed in Manual 1.
**May be open when rolling in Neutral or at low oil temperatures.

Diagnostic Test

1. DETERMINE IF RELATED TCM POWER INPUT DTCS ARE PRESENT

With the scan tool, check for other transmission DTCs.

Are there any TCM Power Input DTCs present also?

Yes

Refer to the Transmission category and perform the appropriate symptom.

Go To 2

2. CHECK IF THE DTC IS CURRENT

With the scan tool, check the DTC EVENT DATA.

Does the DTC EVENT DATA show data for DTC P0846?

Yes

Go To 3

Refer to the Transmission category and perform the appropriate symptom shown in the DTC EVENT DATA.

3. CHECK FOR MULTIPLE DTCS

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

Go To 7

4. CHECK IF ALL PRESSURE SWITCHES READ CLOSED

With the scan tool, check the DTC EVENT DATA for P0846.

NOTE: Make sure to record all DTC EVENT DATA stored in the scan tool for future reference in this test procedure.

Do all the pressure switches read CLOSED in the DTC EVENT DATA for P0846?

Yes

Refer to Transmission category and perform diagnostics for P0882.

Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

Go To 5

5. CHECK IF ALL PRESSURE SWITCHES READ OPEN

In the DTC EVENT DATA recorded earlier, read the state of all pressure switches.

Do all the pressure switches read OPEN?

Yes

Go To 6

Go To 7

6. CHECK FOR LOW LINE PRESSURE

In the DTC 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 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

Replace the Transmission Solenoid/TRS Assembly per the Service Information.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

7. CHECK IF THE DTC SET IN PARK REVERSE OR NEUTRAL

With the scan tool, check the DTC EVENT DATA for P0846.

NOTE: Make sure to record all DTC EVENT DATA stored in the scan tool for future reference in this test procedure.

Does the DTC EVENT DATA show the DTC P0846 set in Park, Reverse, or Neutral?

Yes

Go To 12

Go To 8

8. CHECK IF THE 2C PRESSURE SWITCH READS CLOSED

With the scan tool, check the DTC EVENT DATA for P0846.

NOTE: Make sure to record all DTC EVENT DATA stored in the scan tool for future reference in this test procedure.

Does the DTC EVENT DATA show the 2C Pressure Switch reading CLOSED?

Yes

Go To 10

Go To 9

9. COMPARE THE LINE PRESSURE TO THE DESIRED LINE PRESSURE

Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

Go To 15

10. CHECK THE PCM AND WIRING

Turn the ignition off to the lock position.
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 can result in personal injury or death.

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

Install the Transmission Simulator, Miller tool #8333.
Ignition on, engine not running.
With the Transmission Simulator, turn the Pressure Switch selector switch to the 2C position.
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

Go To 12

11. CHECK THE TRANSMISSION SOLENOID/TRS ASSEMBLY

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.

Where there any problems found?

Yes

Repair as necessary.

Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

Replace the Transmission Solenoid/TRS Assembly per the Service Information.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

12. CHECK THE (T147) 2C PRESSURE SWITCH SENSE CIRCUIT FOR AN OPEN

Turn the ignition off to the lock position.
Disconnect the Transmission Simulator, Miller tool #8333.
Disconnect the PCM C4 harness connector.
Connect Miller tool #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 Miller tool #8815 to perform diagnosis.

Measure the resistance of the (T147) 2C Pressure Switch Sense circuit from the appropriate terminal of Miller tool #8815 to the Transmission Solenoid/TRS Assembly harness connector.

Is the resistance above 5.0 ohms?

Yes

Repair the (T147) 2C Pressure Switch Sense circuit for an open.

Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

Go To 13

13. CHECK THE (T147) 2C PRESSURE SWITCH SENSE CIRCUIT FOR A SHORT TO GROUND

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 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

Go To 14

14. CHECK THE (T147) 2C PRESSURE SWITCH SENSE CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT

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 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

Replace the Powertrain Control Module per the Service Information. With the scan tool, perform the QUICK LEARN procedure.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

15. CHECK IF THE #5 AND/OR #7 CHECK BALL IS CUT OR DAMAGED

Turn the Ignition off to the lock position.
Remove the Valve Body Assembly per the Service Information.
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.
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 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

Go To 16

16. CHECK FOR EXCESSIVE FLUID LEAKAGE WITHIN 2C CLUTCH CIRCUIT

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 for proper repair procedures.

Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

Replace the Transmission Solenoid/TRS Assembly per the Service Information.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)