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P0848



DTC P0843, P0848, or P0873

Diagnostic Instructions

* Perform theDiagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* ReviewStrategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



DTC Descriptors
DTC P0843
- Transmission Pressure Switch 1 Circuit High

DTC P0848
- Transmission Pressure Switch 2 Circuit High

DTC P0873
- Transmission Pressure Switch 3 Circuit High




Diagnostic Fault Information






Typical Scan Tool Data






Circuit/System Description

The pressure switch manifold (PSM) is a multiple switch assembly made up of 3 normally open (N/O) pressure switches and 1 normally closed (N/C) pressure switch. Pressure switch 1 (PS1) monitors shift valve 1 positioning, pressure switch 2 (PS2) monitors shift valve 2 positioning, and pressure switch 2 (PS3) monitors shift valve 3 positioning. The pressure switches communicate the positioning to the transmission control module (TCM).


Conditions for Running the DTC


P0843
* The ignition is ON.
* Ignition voltage is greater than 9.0 V and less than 18 V.
* Engine speed is greater than 200 RPM and less than 7500 RPM for 5 seconds.
* Shift valve 1 is commanded to the ON, or stroked position.



P0848
* The ignition is ON.
* Ignition voltage is greater than 9.0 V and less than 18 V.
* Engine speed is greater than 200 RPM and less than 7500 RPM for 5 seconds.
* Shift valve 2 is commanded to the ON, or stroked position.



P0873
* The ignition is ON.
* Ignition voltage is greater than 9.0 V and less than 18 V.
* Engine speed is greater than 200 RPM and less than 7500 RPM for 5 seconds.
* Shift valve 3 is commanded to the ON, or stroked position.



Conditions for Setting the DTC

P0843

This DTC sets during steady state operation when shift solenoid 1 (SS1) is commanded ON and PS1 indicates OFF for 1 second.

P0848

This DTC sets during steady state operation when shift solenoid 2 (SS2) is commanded ON and PS1 indicates OFF for 1 second.

P0873

This DTC sets during steady state operation when shift solenoid 3 (SS3) is commanded ON and PS1 indicates OFF for 1 second.


Action Taken When the DTC Sets


P0843
* The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL).
* When in a forward range and shifting is completed, the transmission will shift to another forward range, unless the transmission is compromised by overspeeding or direction change, then the transmission will shift to NEUTRAL.
* When in a forward range and the shift is in process the transmission will return to a previous range, except for 1-2 shifts and 2-1 shifts which will be completed.
* While diagnostic response is active, when the shift selector is moved from a forward range to NEUTRAL or from a forward range to REVERSE, then the transmission will shift to NEUTRAL.
* DTC P0843 is stored in TCM history.
* The TCM freezes shift adapts.
* The TCM inhibits torque converter clutch (TCC) engagement.



P0848
* The TCM requests the ECM to illuminate the MIL.
* When in a forward range and shifting is completed, the transmission will shift to another forward range, unless the transmission is compromised by overspeeding, then the transmission will shift to NEUTRAL.
* While diagnostic response is active, when the shift selector is moved from a forward range or reverse to NEUTRAL, the transmission will shift to neutral. If the shift selector is moved to reverse, then the transmission will shift to REVERSE unless the transmission is compromised by overspeeding or a direction change.
* DTC P0848 is stored in TCM history.
* The TCM freezes shift adapts.
* The TCM inhibits TCC engagement.



P0873
* The TCM requests the ECM to illuminate the MIL.
* When in a forward range and shifting is completed, the transmission will shift to another forward range, unless the transmission is compromised by overspeeding then the transmission will shift to NEUTRAL.
* While diagnostic response is active, when the shift selector is moved from a forward range to NEUTRAL, the transmission will shift to neutral. If the shift selector is moved to reverse, then the transmission will shift to REVERSE unless the transmission is compromised by overspeeding or a direction change.
* DTC P0873 is stored in TCM history.
* The TCM freezes shift adapts.
* The TCM inhibits TCC engagement.



Conditions for Clearing the DTC

DTCs P0843, P0848, and P0873 are Type A DTCs.


Diagnostic Aids


P0843
* If DTC P0701 is set in combination with DTC P0843, diagnose P0701 prior to proceeding to DTC P0843.
* You may have to drive the vehicle in order to experience a condition.
* This DTC may indicate that SS1 is mechanically defective.
* When DTCs P0751 and P0843 are set in combination, this may indicate an open circuit condition on the pressure switch 1 circuit or the shift valve 1 is stuck in the destroked position.
* This DTC can be caused by a loss of prime.
* This DTC can be caused by a plugged control main filter.



P0848
* If DTC P0701 is set in combination with DTC P0848, diagnose P0701 prior to proceeding to DTC P0848.
* You may have to drive the vehicle in order to experience a condition.
* This DTC may indicate that SS2 is mechanically defective.
* When DTCs P0756 and P0848 are set in combination, this may indicate an open circuit condition on the pressure switch 2 circuit or the shift valve 2 is stuck in the destroked position.
* This DTC can be caused by a loss of prime.
* This DTC can be caused by a plugged control main filter.



P0873
* If DTC P0701 is set in combination with DTC P0873, diagnose P0701 prior to proceeding to DTC P0873.
* You may have to drive the vehicle in order to experience a condition.
* This DTC may indicate that SS3 is mechanically defective.
* When DTCs P0761 and P0873 are set in combination, this may indicate an open circuit condition on the pressure switch 3 circuit or the shift valve 3 is stuck in the destroked position.
* This DTC can be caused by a loss of prime.
* This DTC can be caused by a plugged control main filter.



Reference Information
Schematic Reference

Automatic Transmission Controls Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

* Transmission General Description (Transmission General Description)
* Transmission Component and System Description (Transmission Component and System Description)
* Electronic Component Description (Electronic Component Description)

Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information


Circuit/System Verification

1. If DTC P0701 is set, diagnose first. Refer to DTC P0701 (P0701) .
2. Engine running, command the transmission through the forward ranges with a scan tool. Compare the TFP Switch 1, TFP Switch 2, and TFP Switch 3 parameters in each forward range with the Pressure Switch Manifold Logic table. Refer to Pressure Switch Manifold (PSM) Logic (Pressure Switch Manifold (PSM) Logic) .
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.



Circuit/System Testing

1. Inspect the transmission fluid level. Refer to Transmission Fluid Check (Transmission Fluid Check) .
2. Ignition OFF, disconnect the X175 harness connector at the transmission.
3. Ignition ON, engine OFF, connect a 3A fused jumper wire to the PS1 signal circuit terminal D to ground, PS2 signal circuit terminal F to ground, and PS3 signal circuit terminal E to ground. Verify with a scan tool the TFP Switch 1, TFP Switch 2, and TFP Switch 3 parameters changed from High to Low when the signal circuit is grounded.

• If not the specified value, test the affected pressure switch signal circuit for an open/high resistance. If circuits test normal, replace the TCM.

4. Ignition OFF, connect the X175 harness connector to the transmission.
5. Remove the pressure switch module from the valve body. Leave the internal wire harness connected to the pressure switch manifold. Refer to Pressure Switch Manifold Replacement (Service and Repair) .
6. Connect a jumper wire to the base of the pressure switch module and ground.
7. Ignition ON, engine OFF, gently push on the PS1, PS2, and PS3 switches. Verify with a scan tool that TFP Switch 1, TFP Switch 2, and TFP Switch 3 parameters changed from High to Low.

• If not the specified value, test the internal wire harness circuits for an open/high resistance. If the circuits test normal, replace the pressure switch module.

8. If all circuits test normal, refer to refer toControl Valve Body Assembly Disassemble (Overhaul) andControl Valve Body Cleaning and Inspection (Overhaul) .

• If valve body inspection is normal, replace the shift solenoid indicated by the DTC, refer toControl Valve Solenoid Replacement (SS1, SS2, SS3, TCC, and MAIN MOD) (Control Valve Solenoid Replacement (SS1, SS2, SS3, TCC, and MAIN MOD))Control Valve Solenoid Replacement (PCS1 and PCS2) (Control Valve Solenoid Replacement (PCS1 and PCS2)) .




Component Testing


Static Testing


Note

You must perform the Circuit/System Testing first.

1. Ignition OFF, remove the PSM from the valve body. Refer to Pressure Switch Manifold Replacement (Service and Repair) .
2. Test for resistance between the PS1 circuit terminal X and the metal base of the PSM. Resistance should be greater than 10 K ohms. If not, replace the PSM.



Repair Instructions

Perform theDiagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Pressure Switch Manifold Replacement (Service and Repair)
* Control Valve Solenoid Replacement (SS1, SS2, SS3, TCC, and MAIN MOD) (Control Valve Solenoid Replacement (SS1, SS2, SS3, TCC, and MAIN MOD))Control Valve Solenoid Replacement (PCS1 and PCS2) (Control Valve Solenoid Replacement (PCS1 and PCS2))
* Control Module References (Programming and Relearning) for TCM replacement, setup, and programming



Repair Verification

If another DTC is present, refer toDiagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code Descriptions) and perform the appropriate diagnostic procedure.

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