41TE NGC

P0846-2/4 PRESSURE SWITCH RATIONALITY







Theory of Operation

The Transmission control 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. The 2/4 pressure switch monitors the fluid pressure to the 2/4 clutch to confirm proper operation of the 2/4 solenoid. If the 2/4 pressure switch is identified as closed in Park or Neutral, the code will immediately be set and normal operation will be allowed for that given ignition start. If the 2/4 pressure switch is identified as closed in 1st or 3rd gear, the code will immediately be set, and the trans will shift to 2nd or 4th gear as appropriate. If the 2/4 pressure switch fails three times (in 1st or 3rd gear) during a single key start, the transmission will go into limp-in and the MIL will illuminate.

- When Monitored:
Whenever the engine is running.

- Set Condition:
The DTC is set if the 2/4 pressure switch is open or closed at the wrong time in a given gear. If the problem is identified for three successive ignition starts, the transmission will go into Limp-in mode and the MIL will turn on after 10 seconds of vehicle operation.





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

PRESSURE SWITCH STATES






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

Are there any Transmission Control Relay, TCM Power Input, or TIPM TCM Power Control circuit DTCs present also?

Yes

- Testing and Inspection 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

- P0944 Perform the appropriate diagnostic procedure.

No

- Go To 3

3. CHECK TO SEE IF P0846 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 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 possible serious or fatal injury.

3. Install the Transmission Simulator 8333A and the Electronic Transmission Adapter kit.

NOTE: Check connectors - Clean/repair as necessary.

4. Ignition on, engine not running.
5. With the Transmission Simulator, turn the Pressure Switch selector to 2/4.
6. With the scan tool, monitor the 2/4 Pressure Switch state while pressing the Pressure Switch Test button on the Transmission Simulator.

Did the 2/4 Pressure Switch state change?

Yes

- Replace the Transmission Solenoid/Pressure Switch Assembly.
- Perform the 40/41TE TRANSMISSION VERIFICATION TEST. 40/41TE Transmission Verification Test.

No

- Go To 5

5. (T47) 2/4 PRESSURE SIGNAL CIRCUIT 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.

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 PCM Pinout Box 8815 to perform diagnosis.

4. Measure the resistance of the (T47) 2/4 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 (T47) 2/4 Pressure Signal circuit for an open.
- Perform the 40/41TE TRANSMISSION VERIFICATION TEST. 40/41TE Transmission Verification Test.

No

- Go To 6

6. (T47) 2/4 PRESSURE SIGNAL CIRCUIT SHORTED TO GROUND




1. Measure the resistance between ground and the (T47) 2/4 Pressure Signal circuit.

Is the resistance below 5.0 Ohms?

Yes

- Repair the (T47) 2/4 Pressure Signal circuit for a short to ground.
- Perform the 40/41TE TRANSMISSION VERIFICATION TEST. 40/41TE Transmission Verification Test.

No

- Go To 7

7. (T47) 2/4 PRESSURE SIGNAL CIRCUIT SHORTED TO VOLTAGE




1. Ignition on, engine not running.
2. With the scan tool in the TIPM, actuate the TCM output.
3. Measure the voltage of the (T47) 2/4 Pressure Signal circuit.

Is the voltage above 0.5 of a volt?

Yes

- Repair the (T47) 2/4 Pressure Signal circuit for a short to voltage.
- Perform the 40/41TE TRANSMISSION VERIFICATION TEST. 40/41TE 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. Check for Service Information Tune-ups or Service Bulletins for any possible causes that may apply. If no problems are found, replace and program the PCM. With the scan tool, perform Quick Learn Quick Learn Procedure.
- Perform the 40/41TE TRANSMISSION VERIFICATION TEST. 40/41TE 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 40/41TE TRANSMISSION VERIFICATION TEST. 40/41TE Transmission Verification Test.

No

- Test Complete.