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DTC P0842 or P0843

DTC P0842 or P0843

Diagnostic Instructions


• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• Diagnostic Procedure Instructions provides an overview of each diagnostic category.


DTC Descriptors

DTC P0842

Transmission Fluid Pressure Switch 1 Circuit Low Voltage

DTC P0843

Transmission Fluid Pressure Switch 1 Circuit High Voltage

Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
Transmission Fluid Pressure Switch 1 Signal P0842 P0843 P0843 -
Transmission Fluid Pressure Switch 3 Signal P0872 P0873 P0873 -
Transmission Fluid Pressure Switch 4 Signal P0877 P0878 P0878 -
Transmission Fluid Pressure Switch 5 Signal P0989 P0990 P0990 -


Typical Scan Tool Data

Transmission Fluid Pressure Switch 1

Circuit Short to Ground Open/High Resistance Short to Voltage
Operating conditions: Engine running, normal operating temperature Parameter Normal Range: 12 volts = High, 0 volts = Low
Transmission Fluid Pressure Switch 1 Signal Low High High


Transmission Fluid Pressure Switch 3

Circuit Short to Ground Open/High Resistance Short to Voltage
Operating conditions: Engine running, normal operating temperature Parameter Normal Range: 12 volts = High, 0 volts = Low
Transmission Fluid Pressure Switch 3 Signal Low High High


Transmission Fluid Pressure Switch 4

Circuit Short to Ground Open/High Resistance Short to Voltage
Operating conditions: Engine running, normal operating temperature Parameter Normal Range: 12 volts = High, 0 volts = Low
Transmission Fluid Pressure Switch 4 Signal Low High High


Transmission Fluid Pressure Switch 5

Circuit Short to Ground Open/High Resistance Short to Voltage
Operating conditions: Engine running, normal operating temperature Parameter Normal Range: 12 volts = High, 0 volts = Low
Transmission Fluid Pressure Switch 5 Signal Low High High


Circuit/System Description

The transmission fluid pressure (TFP) switch 1 is part of the control solenoid valve assembly, which has no serviceable components. The transmission control module (TCM) supplies a signal circuit to the TFP Switch 1. The TFP Switch 1 has an internal case ground. TFP Switch 1 is normally closed or LOW. When oil pressure is present at the TFP Switch 1, the switch is open or HIGH. The normally high clutch pressure control (PC) solenoid 2 controls pressure to the 3-5 reverse clutch regulator valve. The TCM monitors the TFP switch 1 to determine the position of the 3-5 reverse clutch regulator valve. When the 3-5 reverse clutch is commanded OFF, pressure is present on the TFP switch 1. When the 3-5 reverse clutch is commanded ON, the 3-5 reverse clutch regulator valve moves and pressure to the TFP switch 1 is exhausted through the 3-5 reverse clutch regulator valve.

Conditions for Running the DTC


P0842 or P0843

• DTC P0711, P0712, P0713, P0716, P0717, P0722, P0723, P0742, P0751, P0756, P0757, P0973, P0974, P0976, P0977, P1915, or P182E is not set.

• The high side driver is enabled.

• The engine speed is 400 RPM or greater for 5.0 seconds.

• The engine speed is 550 RPM or greater.

• The ignition voltage is 8.6 volts or greater.

• The transmission fluid temperature (TFT) is -7 to +120°C (19-248°F).


Conditions for Setting the DTC

P0842

The TCM detects that the TFP switch 1 signal voltage remains LOW after the 3-5-Reverse clutch transitions from a HIGH pressure state to a LOW pressure state. The TCM counts each incident. The DTC sets when 25 counts are accumulated.

P0843

The TCM detects that the TFP switch 1 signal voltage remains HIGH after the 3-5-Reverse clutch transitions from a LOW pressure state to a HIGH pressure state. The TCM counts each incident. The DTC sets when 35 counts are accumulated.

Action Taken When the DTC Sets


• DTCs P0842 and P0843 are Type C DTCs.

• The TCM freezes transmission adaptive functions for the 3-5-Reverse clutch.


Conditions for Clearing the DTC

DTCs P0842 and P0843 are Type C DTCs.

Diagnostic Aids

A TFP switch may malfunction due to normal debris in the transmission fluid causing a TFP Switch DTC to intermittently set. This type of failure should not be immediately noticeable to a customer, as the switch outputs are used for shift adaptives and do not cause transmission symptoms unless the switch malfunctions continuously for an extended period of time.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference


• Component Connector End Views

• Inline Harness Connector End Views


Description and Operation


• Transmission General Description

• Electronic Component Description for control solenoid valve assembly


Electrical Information Reference


• Circuit Testing

• Connector Repairs

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs


DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

DT-47825-20 Adapter Harness

For equivalent regional tools, refer to Special Tools .

Circuit/System Verification


1. If there are any other transmission related DTCs set, diagnose those DTCs first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle .

2. Engine idling in Park, with parking brake applied and drive wheels chocked.

3. Monitor the Transmission Fluid Pressure Switch 1, Transmission Fluid Pressure Switch 3, Transmission Fluid Pressure Switch 4, and Transmission Fluid Pressure Switch 5 parameters with a scan tool.

4. Place the gear select lever in Park, Reverse, and Neutral range. Verify the TFP Switch parameter states are correct for each range. Refer to Transmission Fluid Pressure Switch Logic .

5. Place the gear select lever in Drive range. Command the shift transmission with a scan tool through all forward ranges. Verify the TFP Switch parameter states are correct for each range. Refer to Transmission Fluid Pressure Switch Logic .

6. After you complete the steps described above, check the diagnostic trouble code is not reset by driving the vehicle according to the conditions for running diagnostic trouble codes (DTC). You can also drive the vehicle according to the conditions you see in Freeze Frame/ Failure records. If the vehicle passes the circuit/system verification procedure, then stop. Do not perform the circuit/system test or component test as this may result in unnecessary part replacement. Refer to Testing for Intermittent Conditions and Poor Connections .


Circuit/System Testing


1.
Note

You must perform the Circuit/System Verification first.


Ignition off. Remove the Q8 control solenoid valve assembly. Refer to Control solenoid valve and transmission control module assembly, replacement .

2. Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

3. Place the Q8 control solenoid valve assembly on a clean work surface near the transmission assembly.

4. Connect the DT-47825-20 harness between the vehicle wire harness X1 20-way transmission electrical connector, and the Q8 control solenoid valve assembly electrical connector.

5. Ignition ON, verify with a scan tool that the Transmission Fluid Pressure Switch 1, Transmission Fluid Pressure Switch 3, Transmission Fluid Pressure Switch 4, and Transmission Fluid Pressure Switch 5 parameters change states when gently pushing on each TFP switch with the eraser end of a pencil.

6. If any TFP Switch parameter does not change states, replace the Q8 control solenoid valve assembly.


Repair Instructions

Note
• Perform the Resetting of the transmission's adaption after all transmission repairs.

• Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .


Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control solenoid valve assembly replacement, setup, or programming