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 provide an overview of each diagnostic category.

DTC Descriptors

DTC P0741: Torque Converter Clutch (TCC) System - Stuck Off

DTC P0751: 1-2 Shift solenoid (SS) Valve Performance - No First or Fourth Gear

DTC P0756: 2-3 Shift Solenoid (SS) Valve Performance - No First or Second Gear

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Hydraulic Performance

1-2 SS Valve Control

P0973

P0973

P0974

P0751, P0752

2-3 SS Valve Control

P0976

P0976

P0977

P0756, P0757

TCC PWM Valve Control

P2764

P2764

P2763

P0741, P0742

Typical Scan Tool Data

Circuit

Normal

Short to Ground

Open/High Resistance

Short to Voltage

Operating Conditions: Engine running, normal operating temperature

Parameter Normal Range: Indeterminate

1-2 Sol. CKT Status

Indeterminate

Short to GND

Open

Short to Volts

2-3 Sol. CKT Status

Indeterminate

Short to GND

Open

Short to Volts

TCC Duty Cycle CKT Status

Indeterminate

Short to GND

Open

Short to Volts

Circuit/System Description

The transmission control module (TCM) controls the torque converter clutch pulse width modulation (TCC PWM) solenoid valve. The solenoid controls the hydraulic fluid for TCC apply and release. When the TCC is fully applied, the engine is coupled directly to the transmission through the TCC. The TCC used is an electronically controlled capacity clutch (ECCC). The TCM normally allows a small amount of slip to occur with the ECCC. When the TCC is engaged, TCC slip speed is maintained at approximately 20-50 RPM. The 1-2 shift solenoid (SS) valve and the 2-3 SS valve are supplied with fused ignition voltage. The ground path is controlled by the TCM. When the TCM commands the solenoid OFF, a ground path is not provided and the filtered line pressure that is fed to the solenoid is exhausted. When the TCM commands the solenoid ON, a ground path is provided and the exhaust port is blocked, stopping the exhaust of line pressure. The TCM identifies a 1-2 SS valve or a 2-3 SS valve condition by monitoring the commanded gear versus gear ratio. Refer to Shift Solenoid Valve State and Gear Ratio .

Conditions for Running the DTC

DTC P0741

    • No TP sensor DTC P0120 or P0220.
    • No ISS DTC P0716 or P0717.
    • No OSS DTC P0722 or P0723.
    • No TCC system stuck ON DTC P0742.
    • The engine speed is greater than 500 RPM for 5 seconds.
    • The transmission fluid temperature (TFT) is between 20-130°C (68-266°F).
    • The engine torque is greater than 50 N·m (37 lb ft).
    • No TCC release switch DTC P0842 or P0843.
    • The calc. throttle position is between 8-90 percent.
    • The TCC PWM solenoid valve is commanded ON.
    • The TCC duty cycle is 65 percent or greater for 5 seconds.
    • The commanded gear is 2nd, 3rd, or 4th.

DTC P0751

    • No TP sensor DTC P0120 or P0220.
    • No ISS DTC P0716 or P0717.
    • No OSS DTC P0722 or P0723.
    • No TCC system stuck ON DTC P0742.
    • The engine speed is greater than 500 RPM for 5 seconds.
    • The TFT is between 20-130°C (68-266°F).
    • The engine torque is greater than 50 N·m (37 lb ft).
    • No 1-2 SS valve electrical DTC P0973 or P0974.
    • No 2-3 SS valve electrical DTC P0976 or P0977.
    • The calc. throttle position is 8 percent or greater.
    • The transmission ISS is 150 RPM or greater.
    • The transmission OSS is 160 RPM or greater.
    • The time since the last gear change is 1.5 seconds.

DTC P0756

    • No TP sensor DTC P0120 or P0220.
    • No ISS DTC P0716 or P0717.
    • No OSS DTC P0722 or P0723.
    • No TCC system stuck ON DTC P0742.
    • The engine speed is greater than 500 RPM for 5 seconds.
    • The TFT is between 20-130°C (68-266°F).
    • The engine torque is greater than 50 N·m (37 lb ft).
    • No 1-2 SS valve electrical DTC P0973 or P0974.
    • No 2-3 SS valve electrical DTC P0976 or P0977.
    • The calc. throttle position is 8 percent or greater.
    • The transmission ISS is 150 RPM or greater.
    • The time since the last gear change is 1.5 seconds.

Conditions for Setting the DTC

DTC P0741

The TCC slip speed is 175 RPM or greater for 5 seconds, 6 times during the same ignition cycle.

DTC P0751

The following conditions both occur twice in 1 trip:

Condition 1

The TCM commands 1st gear and the gear ratio indicated 2nd gear, 1.48:1-1.65:1. for 2 seconds.

Condition 2

The TCM commands 4th gear and the gear ratio indicates 3rd gear, 0.95:1-1.05:1, for 3 seconds.

DTC P0756

The following conditions both occur twice in 1 trip:

Condition 1

The TCM commands 1st gear with the transmission OSS 160 RPM or greater, the TCC slip speed is -20 RPM or greater, and the gear ratio indicates 4th gear, 0.65:1-1.87:1, for 3 seconds.

Condition 2

The TCM commands 2nd gear and the gear ratio indicates 3rd gear, 0.95:1-1.05:1, for 3 seconds.

Action Taken When the DTC Sets

    • DTCs P0741 and P0751 are type B DTCs.
    • DTC P0756 is a type A DTC.
    • The TCM freezes transmission adaptive functions.

DTC P0741

    • The TCM forces the TCC OFF.
    • The TCM inhibits TCC engagement.
    • The TCM inhibits 4th gear if the transmission is in Hot Mode.

DTC P0751

The TCM commands maximum line pressure.

DTC P0756

    • The TCM commands maximum line pressure.
    • The TCM inhibits 1st gear.

Conditions for Clearing the DTC

    • DTCs P0741 and P0751 are type B DTCs.
    • DTC P0756 is a type A DTC.

Diagnostic Aids

If the DTC is cleared, then will not set again when the vehicle is driven, some of the following conditions may exist:

    • Fluid contamination
    • Plugged fluid circuits
    • Restricted fluid circuits

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

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions
    •  Scan Tool Output Controls

DTC Type Reference

    •  Diagnostic Trouble Code (DTC) Type Definitions
    •  Diagnostic Trouble Code (DTC) List/Type

Circuit/System Testing

  1. Perform the Transmission Fluid Check .
  2. Correct the transmission fluid level if the fluid is not at the proper level.
  3. Using the scan tool, clear the DTC. If DTC P0741 was set, operate the vehicle greater than 72 km/h (45 mph) and use the scan tool to command the TCC ON. Observe the TCC Slip Speed parameter on the scan tool. The TCC Slip Speed should be below 175 RPM.
  4. If the TCC Slip Speed is greater than 175 RPM, inspect the following components and repair or replace as necessary:
    • The cooling system for plugging
    • The cooling lines may be pinched. Refer to Transmission Fluid Cooler Flushing and Flow Test .
    • The TCC control valve for sticking
    • The TCC regulator valve for sticking
    • The pressure regulator valve
    • The TCC PWM solenoid valve stuck and O-ring seal for leaks
    • Refer to Control Valve Body Disassemble .
    • The TCC blowoff valve or spring for damage or not seating
    • Refer to Case Assembly Inspection .
    • The TCC signal orifice in the spacer plate plugged
    • The #1 check ball missing or leaking
    • The spacer plate gaskets torn or leaking
    • Refer to Control Valve Body and Spacer Plate Assemble .
    • The turbine shaft seals for leaks
    • Refer to Torque Converter Assembly Removal .
    • The torque converter clutch
    • Refer to Torque Converter Diagnosis .
  5. Using the scan tool, clear the DTC. If DTC P0751 or P0756 is set, drive the vehicle to ensure the TCM commands 1st, 2nd, 3rd, and 4th gears. The ratios should match the commanded gear for all gears. Refer to Shift Solenoid Valve State and Gear Ratio .
  6. If the gear ratios do not match the commanded gear, inspect the following and repair or replace as necessary:

    DTC P0751

    • The 1-2 shift solenoid mechanically stuck OFF
    • A stuck or binding 1-2 shift valve
    • Damaged seals on the shift solenoid valve

    DTC P0756

    • The 2-3 shift solenoid mechanically stuck OFF
    • A stuck or binding 2-3 shift valve
    • Damaged seals on the shift solenoid valve

Component Testing

  1. Perform the Shift Solenoid Leak Test .
  2. If the solenoid fails the shift solenoid leak test, replace the affected solenoid.
  3. Disconnect the wiring harness connector from the affected solenoid. Measure the resistance for the affected solenoid. The resistance should be between 19 and 31 ohms for the 1-2 SS and the 2-3 SS. The resistance should be between 10 and 15 ohms for the TCC PWM solenoid.
  4. If the resistance is not within the specified range, replace the affected solenoid.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

    •  Shift Solenoid Leak Test
    •  1-2 Shift Solenoid Valve Replacement
    •  2-3 Shift Solenoid Valve Replacement
    •  Torque Converter Clutch Pulse Width Modulation Solenoid Replacement
    •  Control Valve Body Disassemble
    •  Case Cover Removal
    •  Case Cover and Gaskets Assemble
    •  Case Cover Components Disassemble