P0878
DTC P0877 or P0878 (Gen 1 with 1.6L (LDE) or 1.8L (LUW))
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC P0877
-
Transmission Fluid Pressure Switch 4 Circuit Low Voltage
DTC P0878
-
Transmission Fluid Pressure Switch 4 Circuit High Voltage
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The transmission fluid pressure (TFP) switch 4 assembly 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 4. The TFP switch 4 has an internal case ground. TFP switch 4 is normally closed, or Low. When oil pressure is present at the TFP switch 4, the switch is open, or High. The normally low clutch pressure control (PC) solenoid 5 controls pressure to the 1-2-3-4 clutch regulator valve. The TCM monitors the TFP switch 4 to determine the position of the 1-2-3-4 clutch regulator valve. When the 1-2-3-4 clutch is commanded OFF, pressure is present on the TFP switch 4. When the 1-2-3-4 clutch is commanded ON, the 1-2-3-4 clutch regulator valve moves and pressure to the TFP switch 4 is exhausted through the 1-2-3-4 clutch regulator valve.
Conditions for Running the DTC
* DTC P0711, P0712, P0713, P0716, P0717, P0722, P0723, P0742, P0751, P0756, P0757, P0973, P0974, P0976, P0977, P182E or P1915 is not set.
* Engine speed is 400 RPM or greater for 5 seconds.
* Ignition voltage is 9.0 volts or greater.
* Transmission fluid temperature (TFT) is -7 to +110°C (19-230°F).
* High Side Driver is ON.
* Engine speed is 550 RPM or greater.
Conditions for Setting the DTC
P0877
The TCM detects that the TFP switch 4 signal voltage remains LOW after the 1-2-3-4 clutch transitions from a HIGH pressure state to a LOW pressure state. The TCM counts each incident. The DTC sets when 12 counts are accumulated.
P0878
The TCM detects that the TFP switch 4 signal voltage remains HIGH after the 1-2-3-4 clutch transitions from a LOW pressure state to a HIGH pressure state. The TCM counts each incident. The DTC sets when 12 counts are accumulated.
Action Taken When the DTC Sets
* DTCs P0877 and P0878 are Type C DTCs.
* TCM freezes transmission adaptive functions on the 1-2-3-4 clutch.
Conditions for Clearing the DTC
DTCs P0877 and P0878 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 condition should not be immediately noticeable to a customer, as the switch outputs are used for shift adaptive pressure 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 Electrical Diagrams
Connector End View Reference
* Component Connector End Views Fuel Pump and Level Sensor Assembly
* Inline Harness Connector End Views X100
Description and Operation
* Transmission General Description Transmission General Description
* Electronic Component Description Electronic Component Description for control solenoid valve assembly
* Transmission Component and System Description Transmission Component and System Description
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
Warning:
Refer to Parking Brake and Drive Wheels Warning Parking Brake and Drive Wheels Warning.
1. Engine idling in PARK with parking brake applied, and drive wheels chocked.
2. Verify the Transmission Fluid Pressure Switch 1, Transmission Fluid Pressure Switch 3, Transmission Fluid Pressure Switch 4, and Transmission Fluid Pressure Switch 5 parameters parameter states are correct for the Park, Reverse, and Neutral gear select lever positions. Refer to Transmission Fluid Pressure Switch Logic Transmission Fluid Pressure Switch Logic.
• If any parameter value is not correct for a given gear range
Refer to Circuit/System Testing below.
• If the parameter values are correct for all gear ranges
3. Verify the Transmission Fluid Pressure Switch 1, Transmission Fluid Pressure Switch 3, Transmission Fluid Pressure Switch 4, and Transmission Fluid Pressure Switch 5 parameter states are correct for each forward range with the gear select lever in Drive, using the scan tool to command all forward ranges. Refer to Transmission Fluid Pressure Switch Logic Transmission Fluid Pressure Switch Logic.
• If any parameter value is not correct for a given gear range
Refer to Circuit/System Testing below.
• If the parameter values are correct for all gear ranges
4. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, refer to Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections.
Circuit/System Testing
1. Ignition OFF, remove the Q8 control solenoid valve assembly, filter plate, channel plate and spacer plate. Refer to Control Solenoid Valve and Transmission Control Module Assembly Replacement Service and Repair.
2. Inspect the Q8 control solenoid valve assembly, filter plate, channel plate, and spacer plate for debris and blocked orifices.
• If debris or blocked orifices are observed
Clean or replace as necessary.
• If no debris or blocked orifices are observed
Replace the Q8 control solenoid valve assembly.
Repair Instructions
Note:
* Perform the Transmission Adaptive Values Learn Programming and Relearning following all transmission related repairs.
* Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection (Gen 1 with 1.4L - LCU, 1.6L - LDE or LFJ, 1.8L - LUW) Control Solenoid Valve and Transmission Control Module Assembly Inspection (Gen 1 with 1.4L - LCU, 1.6L - LDE or LFJ, 1.8L - LUControl Solenoid Valve and Transmission Control Module Assembly Inspection (Gen 2 with 1.4L - LUV) Control Solenoid Valve and Transmission Control Module Assembly Inspection (Gen 2 with 1.4L - LUV).
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
Control Module References Control Module References for control solenoid valve assembly replacement, setup, or programming.