P0748
DTC P0748 or P0961-P0963
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 P0748
- Line Pressure Control Solenoid Valve System Performance
DTC P0961
- Line Pressure Control Solenoid Valve System Performance
DTC P0962
- Line Pressure Control Solenoid Valve Control Circuit Low Voltage
DTC P0963
- Line Pressure Control Solenoid Valve Control Circuit High Voltage
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
Line pressure control solenoid (SLT) is part of the front valve body. SLT regulates the transmission fluid line pressure in accordance with the value decided in the transmission control module (TCM) based on throttle opening signal and engine torque. Through this, it controls operating hydraulic pressure to the clutch and brakes for smooth shifting. The TCM varies the current to the normally SLT from 0.1 A for maximum line pressure, to 1.1 A for minimum line pressure. As a fail-safe function, if SLT abnormality occurs, the TCM will disable the current. In that case the line pressure is maximized.
Conditions for Running the DTC
P0748
* The ignition voltage is 10.2-15.5 V.
* The engine speed is greater than 400 RPM for 2 s.
* The transmission is not in emergency mode.
* Driving in D range.
* TCM communication is normal.
* DTCs P0962 and P0963 are not set.
P0961
* The ignition voltage is 10.2-15.5 V.
* The engine speed is greater than 400 RPM for 2 s.
* The transmission is not in emergency mode.
* Driving in D range.
* TCM communication is normal.
* The Automatic Transmission Fluid Temperature is more than 20°C (68°F)
* SLT current is more than 0.85 A.
* SLT current is not changed.
P0962
* The ignition voltage is 10.2-15.5 V.
* The engine speed is greater than 400 RPM for 2 s.
* The transmission is not in emergency mode.
* Driving in D range.
* TCM communication is normal.
* DTC P0963 is not set.
P0963
* The ignition voltage is 10.2-15.5 V.
* The engine speed is greater than 400 RPM for 2 s.
* The transmission is not in emergency mode.
* Driving in D range.
* TCM communication is normal.
* DTC P0962 is not set.
Conditions for Setting the DTC
P0748
Deviation between commanded current and feedback current.
P0961
The TCM detects the error current more than 80 mA for 2.75 ms.
P0962
The TCM detects at least 5 times less than 23 mA current consumption of the SLT control circuit for 100 ms.
P0963
The TCM detects at least 5 times more than 1.333 A current consumption of the SLT control circuit for 100 ms.
Action Taken When the DTC Sets
P0748, P0961
* DTC P0961 is a Type B DTC.
* The TCM turns OFF all solenoids.
* The TCM allows the vehicle after a stop to operate only in the second gear and "R" range.
P0962, P0963
* DTCs P0962 and P0963 are Type B DTCs.
* No self learning function.
* The TCM turns OFF all solenoids.
* The TCM allows the vehicle after a stop to operate only in the second gear and "R" range.
Conditions for Clearing the DTC
P0748, P0961
* DTC P0963 is a Type B DTC.
* The TCM detects the error current less than 50 mA for 2.75 ms.
P0962, P0963
* DTCs P0962 and P0963 are Type B DTCs.
* The current consumption of the SLT control circuit is 0.1-1.1 A for 500 ms.
Diagnostic Aids
When attempting to set solenoid electrical DTCs, ensure the TCM is warmed up and the transmission is operated in 2nd gear long enough to ensure a 3°C (5°F) increase in TCM substrate temperature. This will place the TCM under the optimal conditions to test solenoid electrical DTCs.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
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)
Description and Operation
Transmission Component and System Description (Transmission Component and System Description)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ensure the transmission fluid temperature is between 50-80°C (122-176°F).
2. Operate the vehicle in 2nd gear long enough to ensure at least a 3°C (5°F) rise in transmission fluid temperature, then operate the vehicle in Park for 5 s.
3. Observe the scan tool Line Pressure Control Solenoid Valve Current parameter, the reading should be between 0.1-1.1 A.
• If the parameter in not within specified range or if the DTC resets, go to Circuit/System Testing.
Circuit/System Testing
Command the Line Pressure Control Solenoid Valve with a scan tool. The value should change from 0.0-1.1 A.
If the value does not change, turn ignition OFF, remove the K71 Transmission Control Module. Connect a test lamp between the low reference circuit terminal 1 X2 at the K71 Transmission Control Module and the voltage supply component circuit terminal 3 X2 at the K71 Transmission Control Module. Command the Line Pressure Control Solenoid Valve with a scan tool. The test lamp has to illuminate brighter with increasing current.
If the test lamp always illuminate or always does not illuminate, replace the K71 Transmission Control Module.
Component Testing
Static Test
1. Ignition OFF, remove the K71 Transmission Control Module.
2. Test for 5-5.6 ohm at 20°C (68°F) between the low reference circuit terminal 1 X2 and the voltage supply circuit terminal 3 X2.
• If less than the specified range, test the wiring harness for internal short. If the circuit test normal, replace the Q23 Line Pressure Control Solenoid Valve.
3. Test for infinite resistance between each terminal and the low reference circuit terminal 1 X2 and also to the voltage supply circuit terminal 3 X2.
• If less than the specified range, replace the wiring harness.
4. If all circuit test normal, perform the Control Solenoid Valve Inspection (M36 and MXE) (AF40-6 - Automatic Transmission).
• If the inspection test normal, replace the valve body assembly.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Control valve body replacement-Refer to Control Valve Body Replacement (Control Valve Body Replacement) for replacement, setup and programming.
* TCM-Refer to Control Module References (Programming and Relearning) for replacement, setup and programming.
* Perform the Transmission Adaptive Functions (Transmission Adaptive Functions).
* Wiring harness-Refer to Automatic Transmission Wiring Harness Replacement (Service and Repair) for replacement.