P0846-2/4 PRESSURE SWITCH RATIONALITYFor a complete wiring diagram Refer to Section 8W.Theory of OperationThe 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.
Possible CausesRELATED TIPM TCM POWER CONTROL CIRCUIT DTCS PRESENTLOSS OF PRIME DTC PRESENT(T47) 2/4 PRESSURE SWITCH SENSE CIRCUIT OPEN(T47) 2/4 PRESSURE SWITCH SENSE CIRCUIT SHORT TO GROUND(T47) 2/4 PRESSURE SWITCH SENSE CIRCUIT SHORT TO VOLTAGETRANSMISSION SOLENOID/PRESSURE SWITCH ASSEMBLYPOWERTRAIN CONTROL MODULE
Always perform the 42RLE Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC
- 42RLE - STANDARD PROCEDURE)
Diagnostic Test1.DETERMINING IF RELATED TIPM TCM POWER CONTROL CIRCUIT DTCS PRESENTWith the scan tool, read TIPM DTCs.Are there any TIPM TCM Power Control Circuit DTCs present also?YesRefer to the Transmission category and perform the appropriate symptom.NoGo To 22.CHECK FOR LOSS OF PRIME DTCWith the scan tool, check for other Transmission DTCs.Is the DTC P0944 present also?YesRefer to the Transmission category and perform the appropriate diagnostic procedure.NoGo To 33.CHECK TO SEE IF P0846 IS CURRENTWith the scan tool, view DTCs.Is the status Active for this DTC or is the STARTS SINCE SET counter 2 or less?YesGo To 4NoGo To 84.PCM AND WIRINGTurn the ignition off to the lock position.Remove the Ignition Switch Feed fuse from the TIPM.Removal of the Ignition Switch Feed fuse from the TIPM will prevent the vehicle from being started in gear. 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 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?YesReplace the Transmission Solenoid/Pressure Switch Assembly per the Service Information.Perform 42RLE TRANSMISSION VERIFICATION TEST (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)NoGo To 55.(T47) 2/4 PRESSURE SWITCH SENSE CIRCUIT OPENTurn the ignition off to the lock position.Disconnect the PCM C4 harness connector.Disconnect the Transmission Solenoid/Pressure Switch Assembly harness connector.Check connectors - Clean/repair as necessary.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 (T47) 2/4 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?YesRepair the (T47) 2/4 Pressure Switch Sense circuit for an open.Perform 42RLE TRANSMISSION VERIFICATION TEST (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)NoGo To 66.(T47) 2/4 PRESSURE SWITCH SENSE CIRCUIT SHORT TO GROUNDMeasure the resistance between ground and the (T47) 2/4 Pressure Switch Sense circuit.Is the resistance below 5.0 ohms?YesRepair the (T47) 2/4 Pressure Switch Sense circuit for a short to ground.Perform 42RLE TRANSMISSION VERIFICATION TEST (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)NoGo To 77.(T47) 2/4 PRESSURE SWITCH SENSE CIRCUIT SHORT TO VOLTAGEIgnition on, engine not running.With the scan tool under TIPM, actuate the Transmission.Measure the voltage of the (T47) 2/4 Pressure Switch Sense circuit.Is the voltage above 0.5 volts?YesRepair the (T47) 2/4 Pressure Switch Sense circuit for a short to voltage.Perform 42RLE TRANSMISSION VERIFICATION TEST (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)NoUsing 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. If no problems are found, replace and program the PCM per the Service Information. With the scan tool, perform QUICK LEARN.Perform 42RLE TRANSMISSION VERIFICATION TEST (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)8.INTERMITTENT WIRING AND CONNECTORSThe 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?YesRepair as necessary.Perform 42RLE TRANSMISSION VERIFICATION TEST (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)NoTest Complete.