P0701
DTC P0701
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 Descriptor
DTC P0701
- Transmission Control System Performance
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, pressure switch 3 (PS3) monitors shift valve 3 positioning, and pressure switch 4 (PS4) monitors the position of the manual selector valve. The pressure switches communicate the positioning to the transmission control module (TCM). The position of the shift valves 1, 2, and 3 is controlled by 3 normally closed shift solenoids. When energized, SS1 directs fluid pressure to shift valve 1, SS2 directs fluid pressure to shift valve 2, and SS3 directs fluid pressure to shift valve 3, which strokes the shift valves. When the shift valve is stroked, an exhaust passage is blocked and fluid pressure to the normally open PS1, PS2, or PS3 increases. When the selector valve is in neutral or any forward position, an exhaust passage is blocked and fluid pressure to the normally closed PS4 increases.
Conditions for Running the DTC
Condition 1
* The test is enabled after engine start-up and runs as part of the transmission hydraulic initialization.
* The transmission fluid temperature is greater than -25°C (-13°F).
Condition 2
* The engine speed is less than 1000 RPM.
* The transmission turbine speed is less than 1000 RPM.
* The output speed is less than 200 RPM.
* Commanded gear is neutral, reverse or first.
* The transmission fluid temperature is greater than -25°C (-13°F).
Conditions for Setting the DTC
Condition 1:
* At start-up, all pressure switches do not indicate pressure.
* Engine speed is greater than 500 RPM for 6 seconds or 400 RPM for 15 seconds.
* The selected range is not neutral or park for 4 seconds.
Condition 2:
* Any 2 of the PS1, PS2 or PS3 switches indicate that the corresponding shift valve was stroked and a loss pressure is indicated.
* Transmission turbine speed is greater than 400 RPM.
* Transmission output speed is less than 80 RPM.
Action Taken When the DTC Sets
* DTC P0701 is a Type C DTC.
* Range is inhibited, and the driver is required to use the gear selector to re-select the range.
Conditions for Clearing the DTC
DTC P0701 is a Type C DTC.
Diagnostic Aids
* A plugged control main filter may cause the DTC to set.
* A cracked internal suction filter tube or damaged tube seal may cause the DTC to set.
* A stuck lube regulator valve may cause the DTC to set.
* Must attempt to select range in order to experience a condition.
* May have to wait several hours prior to restarting vehicle to experience the condition.
* This DTC is most likely the result of no pressure and not wiring or the pressure switch module.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics (Allison - Automatic Transmission)
Connector End View Reference
* Component Connector End Views (Connector End Views By Name)
* Inline Harness Connector End Views (Connector End Views By Number)
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 (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
Chock the wheels to prevent the vehicle from moving. Failure to chock the wheels can cause personal injury when the electrical system is repaired.
1. Perform theTransmission Fluid Level and Condition Check (Transmission Fluid Level and Condition Check) to verify correct fluid level and condition.
2. Engine running, command the transmission through the forward ranges with a scan tool. Compare the TFP Switch 1, TFP Switch 2, TFP Switch 3, and TFP Switch 4 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
Note: You must perform the Circuit/System Verification first.
1. Perform a line pressure test. Refer to Line Pressure Check (Line Pressure Check).
• If line pressure is low in all ranges, refer to Low Main Line Pressure in All Ranges (Low Main Line Pressure in All Ranges).
• If line pressure is low in a specific range or ranges, refer to Low Main Line Pressure in Specific Ranges, Normal Pressure in Other Ranges (Low Main Line Pressure in Specific Ranges, Normal Pressure in Other Ranges).
2. Remove and Replace the control main filter, refer to Automatic Transmission Fluid and Filter Replacement (Automatic Transmission Fluid and Filter Replacement).
3. Engine running, command the transmission through the forward ranges with a scan tool. Compare the TFP Switch 1, TFP Switch 2, TFP Switch 3, and TFP Switch 4 parameters in each forward range with the Pressure Switch Manifold Logic table. Refer to Pressure Switch Manifold (PSM) Logic (Pressure Switch Manifold (PSM) Logic).
4. Ignition OFF, remove the X175 harness connector at the transmission.
1. Ignition ON, engine OFF, connect a 3A fused jumper wire to the PS1 signal circuit terminal D to ground
2. PS2 signal circuit terminal F to ground
3. PS3 signal circuit terminal E to ground
4. PS4 signal circuit terminal K to ground
5. Verify with a scan tool the TFP Switch 1, TFP Switch 2, TFP Switch 3, and TFP Switch 4 parameters changed from High to Low when the signal circuit is grounded
• If not the specified value, test the affected pressure switch signal for an open/high resistance and short to ground. If circuits test normal, replace the TCM.
5. Ignition OFF, connect the X175 harness connector to the transmission.
6. Remove the transmission oil pan. Refer to Oil Pan Replacement (Allison - Automatic Transmission).
7. 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).
8. Connect a jumper wire to the base of the pressure switch module and ground.
9. Ignition ON, engine OFF, gently push on the PS1, PS2, PS3, and PS4 switches with the eraser end of a pencil. Verify with a scan tool that the TFP Switch 1, TFP Switch 2, and TFP Switch 3 parameters changed from High to Low and TFP Switch 4 parameter changed from Low to High.
• If not the specified value, test the internal wire harness circuits for an open/high resistance or short to ground. If the circuits test normal, replace the pressure switch module.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Wiring Harness Replacement (Allison - Automatic Transmission)
* Pressure Switch Manifold Replacement (Service and Repair)
* Control Module References (Control Module References) for TCM replacement, setup, and programming
Repair Verification
If another DTC is present, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code (DTC) List - Vehicle) and perform the appropriate diagnostic procedure.