GM Service Manual Online
For 1990-2009 cars only

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 P0877:  Transmission Fluid Pressure (TFP) Switch 4 Circuit Low Voltage

DTC P0878:  Transmission Fluid Pressure (TFP) Switch 4 Circuit High Voltage

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

TFP Switch 1 Signal

P0842

P0843

P0843

--

TFP Switch 3 Signal

P0872

P0873

P0873

--

TFP Switch 4 Signal

P0877

P0878

P0878

--

TFP Switch 5 Signal

P0989

P0990

P0990

--

Typical Scan Tool Data

TFP Switches

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Operating Conditions: Engine running, normal operating temperature

Parameter Normal Range: 12 Volts = Hi, 0 Volts = Low

TFP Switch 1

Low

Hi

Hi

TFP Switch 3

Low

Hi

Hi

TFP Switch 4

Low

Hi

Hi

TFP Switch 5

Low

Hi

Hi

Circuit/System Description

The transmission fluid pressure (TFP) switch 4 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 4 on the TFP switch 4 signal circuit; the TFP switch 4 has an internal case ground. TFP switch 4 is normally closed, Low. When oil pressure is present at the TFP switch 4, the switch is open, high. The normally low clutch pressure control (PC) solenoid 4-5 controls the transmission fluid to the 1-2-3-4 clutch. The TCM monitors the normally closed TFP switch 4 signal circuit to determine the 1-2-3-4 clutch status.

Conditions for Running the DTC

    • No TFT DTCs P0711, P0712, or P0713.
    • No pressure control solenoid electrical DTCs P0965, P0966, P0967, P0969, P0970, P0971, P2719, P2720, P2721, P2728, P2729, or P2730.
    • No shift solenoid electrical DTCs P0973, P0974, P0976, or P0977.
    • No IMS DTCs P1825 or P1915.
    • Ignition voltage is between 8.6 volts and 19.0 volts.
    • The transmission fluid temperature (TFT) is 20-150°C (68-302°F).

Conditions for Setting the DTC

P0877

The TCM detects that the TFP switch 4 signal voltage remains low, 0 volts when the 1-2-3-4 clutch is commanded ON for 5.5 seconds or greater.

P0878

The TCM detects that the TFP switch 4 signal voltage is high, 12 volts when the 1-2-3-4 clutch is commanded OFF for 5.5 seconds or greater.

Action Taken When the DTC Sets

    • DTCs P0877 and P0878 are Type C DTCs.
    • The TCM freezes transmission adaptive functions.

Conditions for Clearing the DTC

DTCs P0877 and P0878 are Type C DTCs.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

    •  Automatic Transmission Inline 20-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

  1. Ensure the TFT is near the temperature displayed in the Failure Records.
  2. Start the engine and place the transmission range selector in D6.
  3. Observe the TFP switch 4 parameter while commanding 4th gear and then commanding 5th gear with the scan tool. The TFP Switch 4 should transition from High in 4th gear to Low in 5th gear.
  4. If the TFP switch 4 parameter state does not change, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .
    If no concerns are found, replace the control solenoid (w/body and TCM) valve 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.

  1. Control solenoid (w/body and TCM) valve assembly replacement - refer to Control Module References for replacement, setup, and programming.
  2. Perform the Service Fast Learn Adapts .