DTC P0842 or P0843. Cadillac SLS 2008

For 1990-2009 cars only

Makes 🢒 Cadillac 🢒 2008 🢒 SLS 🢒 DTC 🢒 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 (TFP) Switch 1 Circuit Low Voltage

DTC P0843: Transmission Fluid Pressure (TFP) Switch 1 Circuit High Voltage

The transmission fluid pressure (TFP) switch 1 is part of the control solenoid (w/body and TCM) valve assembly and is not serviced separately. The TCM supplies 12 volts to the TFP Switch 1 on the TFP Switch 1 signal circuit; the TFP Switch 1 has an internal case ground. TFP Switch 1 is normally closed, Low. When oil pressure is present at the TFP Switch 1, the switch is Open, High. The normally high clutch pressure control (PC) solenoid 2 controls the transmission fluid to the 3-5-R clutch. The TCM monitors the normally closed TFP Switch 1 signal circuit to determine the 3-5-R clutch status.

Conditions for Running the DTC

•	DTCs P0711, P0712 or P0713 are not set.

•	No DTCs P0965, P0966, P0967, P0968, P0969, P0970, or P0971.

•	No DTCs P0973, P0974, P0976, P0977, P2719, P2720, P2728, P2729, or P2730.

•	No DTC P1825 or P1915.

•	DTC P2721 is not set.

•	The Transmission Fluid Temperature (TFT) is between 20 and 150°C (68 and 302°F).

•	The engine speed is greater than or equal to 1,100 RPM.

Conditions for Setting the DTC

P0842

•	Without Start Test

•	Regular Test

-	The TCM does not turn off during the process.

-	The PC solenoid valve 2 hydraulic is 100 kPa or less for 0.45 second.

-	The pressure switch remain closed for 5.5 seconds.

P0843

•	Without Start Test

•	Regular Test

-	The TCM does not turn off during the process.

-	Engine running.

-	The PC solenoid valve 2 hydraulic is 600 kPa or greater for 1 second.

-	Keep the pressure switch OFF for 5.5 seconds.

Action Taken When the DTC Sets

•	DTCs P0842 and P0843 are Type C DTCs.

•	The TCM freezes transmission adaptive functions.

Conditions for Clearing the DTC

DTCs P0842 and P0843 are Type C DTCs.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

•	Automatic Transmission Inline 16-Way Connector End View

•	Automatic Transmission Internal Connector End Views

•	Automatic Transmission Related Connector End Views

DTC Type Reference

•	Diagnostic Trouble Code (DTC) Type Definitions

•	Diagnostic Trouble Code (DTC) List/Type

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

Circuit/System Verification

If there are any other transmission related DTCs set, diagnose those DTCs first.

Circuit/System Testing

Ensure the TFT is near the temperature displayed in the Failure Records.
Start the engine and observe the TFP Switch 1 parameter while moving the range selector lever from Park to Reverse. The TFP Switch 1 should transition from Hi in Park to Low in Reverse.

⇒	If the TFP Switch 1 parameter does not change, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

⇒	If no concerns are found, replace the control solenoid valve and TCM assembly.

Component Testing

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

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Service Fast Learn Adapts

•	Control Module References for TCM replacement, setup, and programming