P0846
P0846 - 2/4 Pressure Switch Rationality
For a complete wiring diagram, refer to.
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. 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 P or N, the code will immediately be set and normal operation will be allowed for that given key start. If the problem is identified for 3 successive ignition cycles, the transmission will go into limp-in mode.
• When Monitored: Whenever the engine is running.
• Set Condition: The DTC is set if one of the pressure switches are open or closed at the wrong time in a given gear. If the problem is identified for 3 successive key 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. Refer to => Non-DTC Based Diagnostics. Pre-Diagnostic Troubleshooting Procedure
Pressure Switch States
Test Step 1 - Determine if Related TCM DTCs are Present
• With the scan tool, read DTCs
Are there any TCM Power Input DTCs present also?
Yes
• Refer to the transmission category and perform the appropriate diagnostic procedures.
No
• Go to Test Step 2.
Test Step 2 - Check for Loss of Prime DTC
• With the scan tool, read DTCs.
Is the DTC P0944 present also?
Yes
• Refer to the transmission category and perform the appropriate diagnostic procedures.
No
• Go to Test Step 3.
Test Step 3 - Determine if P0846 is Current
• With the scan tool, read DTCs.
Is the status active for this DTC or is the starts since set counter 2 or less?
Yes
• Go to Test Step 4.
No
• Go to Test Step 8.
Test Step 4 - PCM and Wiring
The starter solenoid relay must be removed from the TIPM. Failure to do so can result in possible serious or fatal injury.
Removal of the starter solenoid relay from the TIPM will prevent the vehicle from being started in gear.
• Turn the ignition OFF to the lock position.
• Remove the starter solenoid relay from the TIPM.
• Install the transmission simulator, Miller tool #8333 and the electronic transmission adapter kit.
• Check connectors - Clean/repair as necessary.
• Ignition ON, engine not running.
• With the transmission simulator, turn the pressure switch selector to 2/4.
• 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/TRS assembly.
• Perform the Transmission Verification Test. Refer to => Non-DTC Based Diagnostics. Transmission Verification Test
No
• Go to Test Step 5.
Test Step 5 - 2/4 Pressure Signal Circuit Open
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 Special Tool #8815 to perform diagnosis.
• Turn the ignition OFF to the lock position.
• Disconnect the PCM C4 harness connector.
• Disconnect the transmission solenoid/TRS assembly harness connector.
• Measure the resistance of the 2/4 pressure signal circuit from the appropriate terminal of Miller tool #8815 and the transmission solenoid/TRS assembly harness connector.
Is the resistance more than 5.0 ohms?
Yes
• Repair the 2/4 pressure signal circuit for an open.
• Perform the Transmission Verification Test. Refer to => Non-DTC Based Diagnostics. Transmission Verification Test
No
• Go to Test Step 6.
Test Step 6 - 2/4 Pressure Signal Circuit Short to Ground
• Measure the resistance between ground and the 2/4 pressure signal circuit.
Is the resistance less than 5.0 ohms?
Yes
• Repair the 2/4 pressure signal circuit for a short to ground.
• Perform the Transmission Verification Test. Refer to => Non-DTC Based Diagnostics. Transmission Verification Test
No
• Go to Test Step 7.
Test Step 7 - 2/4 Pressure Signal Circuit Short to Voltage
• Ignition ON, engine not running.
• With the scan tool in the TIPM, actuate the TCM output.
• Measure the voltage of the 2/4 pressure signal circuit.
Is the voltage more than 0.5 volts?
Yes
• Repair the 2/4 pressure signal circuit for a short to voltage.
• Perform the Transmission Verification Test. Refer to => Non-DTC Based Diagnostics. Transmission Verification Test
No
• Replace and program the powertrain control module. With the scan tool perform Quick Learn.
• Perform the Transmission Verification Test. Refer to => Non-DTC Based Diagnostics. Transmission Verification Test
Test Step 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
• Repair as necessary.
• Perform the Transmission Verification Test. Refer to => Non-DTC Based Diagnostics. Transmission Verification Test
No
• Test Complete.