Diagnostic Routine P
Diagnostic Routine P
Diagnostic Overview
P0748, P0960, P0961, P0962, P0963
Refer to Wiring Diagram Set 30 for schematic and connector information Electrical Diagrams.
Normal Operation and Fault Conditions
The TCM (Transmission Control Module) controls the hydraulic line pressure by varying the amount of current applied to the LPC (Line Pressure Control) solenoid. When no current is applied to the LPC (Line Pressure Control) solenoid, the LPC (Line Pressure Control) solenoid is fully opened, resulting in the maximum amount of hydraulic pressure to the Main Pressure Regulator Valve. When maximum current is applied, the LPC (Line Pressure Control) solenoid is fully closed, resulting in minimum pressure to the Main Pressure Regulator Valve.
When the LPC (Line Pressure Control) solenoid or LPC (Line Pressure Control) solenoid circuits are faulted, the following symptoms may be present:
- Failure Mode Effect Management action opens the transmission solenoid power control, removing power from all solenoids (get PARK, REVERSE, NEUTRAL and 5th gear as the only forward gear with TCC (Torque Converter Clutch) open/un-applied) which provides maximum line pressure.
- Harsh engagements.
- Poor launch performance (due to 5th gear drive away).
- No TCC (Torque Converter Clutch) apply.
- No shifts.
DTC Fault Trigger Conditions
Visual Inspection and Diagnostic Pre-checks
- Inspect for damaged wiring harness
- Inspect for loose or damaged connectors
Pinpoint Test
NOTE: If the scan tool is unable to communicate with the TCM (Transmission Control Module), REFER to Diagnostic Routine AB: The Transmission Control Module (TCM) Does Not Respond To The Scan Tool Diagnostic Routine AB.
1. INSPECT FOR CORROSION OR TERMINAL DAMAGE
1. Ignition OFF.
2. Disconnect 6F35 Transmission C1520A.
3. Disconnect the TCM (Transmission Control Module).
4. Use a mirror to inspect both ends of each connector for damage or pushed out pins, corrosion, loose wires and missing or damaged seals.
Are both connectors free of any damage, corrosion, pushed-out terminals, loose wires, or missing or damaged seals?
2. CHECK THE LPC (Line Pressure Control) SOLENOID CIRCUIT FOR AN OPEN
1. Measure:
Is the resistance less than 5 ohms?
3. CHECK THE LPC (Line Pressure Control) SOLENOID CIRCUIT FOR A SHORT TO GROUND
1. Measure:
2. Repeat the measurement while wiggling the wiring harness and connectors.
Is the resistance greater than 10,000 ohms?
4. CHECK THE LPC (Line Pressure Control) SOLENOID CIRCUIT FOR A SHORT TO POWER
1. Ignition ON.
2. Measure:
Is any voltage present?
5. CHECK THE RESISTANCE OF THE LPC (Line Pressure Control) SOLENOID FIELD CIRCUIT
1. Ignition OFF.
2. Measure and record:
3. Compare the recorded resistance value to the chart below.
Temperature to Resistance - LPC (Line Pressure Control) Solenoid
Is the resistance within specifications?
6. CHECK THE SOLENOID BODY LEADFRAME FOR AN OPEN
1. Remove the solenoid body leadframe. REFER to Solenoid Body Leadframe .
2. Measure:
Is the resistance less than 5 ohms?
7. CHECK THE TCM (Transmission Control Module) FOR CORRECT OPERATION
1. Prior to reconnecting any previously disconnected connector:
- inspect connector(s) (including any inline connectors) for pushed-out, loose or spread terminals and loose or frayed wire connections at terminals.
- inspect wire harness for any damaged, pinched, cut or pierced wires.
2. Connect the 6F35 Transmission C1520A.
3. Connect the TCM (Transmission Control Module).
4. Ignition ON.
5. Using a scan tool, perform TCM (Transmission Control Module) self-test to retrieve DTCs (Diagnostic Trouble Codes).
Is the concern still present?
