GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2008 🢒 Lucerne 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC P0741, P0751, or P0756

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 provides 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

Typical Scan Tool Data

1-2 and 2-3 Shift Solenoid Valve

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

Torque Converter Clutch (TCC) Solenoid

The torque converter clutch pulse width modulated (TCC PWM) solenoid is a normally closed solenoid used to control the apply and release of the converter clutch. When the vehicle operating conditions are appropriate to apply the TCC, the transmission control module (TCM) immediately increases the duty cycle to approximately 42 percent. The TCM then ramps the duty cycle to approximately 90 percent to achieve full TCC apply pressure. When the TCC is fully applied, the engine is coupled directly to the transmission through the TCC. The TCM normally allows a small amount of slip to occur. When the TCC is engaged, TCC slip speed is maintained at approximately 20-50 RPM.

The 1-2 Shift and 2-3 Shift Solenoids

The 1-2 shift solenoid (SS) valve and the 2-3 SS valves control transmission fluid pressure acting on the shift valves to position the valves for the appropriate gear. The 1-2 SS and the 2-3 SS valves are normally-open exhaust valves located on the control valve body. A fused circuit supplies ignition voltage to the 1-2 SS valve and the 2-3 SS valve. The TCM commands the solenoid ON or OFF by switching the ground path. The TCM identifies a 1-2 SS valve or a 2-3 SS valve condition by monitoring the commanded gear versus gear ratio.

Conditions for Running the DTC

P0741

    • DTCs P0120, P0121, P0122, P0123, P0220, P0221, P0222, P0223, P0225, P0226, P0227, P0228, P0716, P0717, P0722, P0723, P0742, P0842, P0843, P1120, P1121, P1122, P1125, P1280, P1281, P1282, P1283, P1285, P1286, P1287, or P1288 are not set.
    • The ignition voltage is between 8 and 18 volts.
    • The engine speed is between 500 and 6,500 RPM for 5 seconds.
    • The transmission fluid temperature (TFT) is between 20-130°C (68-266°F).
    • The engine torque is between 50-1,492 N·m (37-1,100 lb ft).
    • The throttle position is between 2-90 percent.
    • The TCC duty cycle is 65 percent or greater for 2 seconds.
    • The commanded gear is 3rd or 4th.

P0751 and P0756

    • DTCs P0120, P0121, P0122, P0123, P0220, P0221, P0222, P0223, P0225, P0226, P0227, P0228, P0716, P0717, P0722, P0723, P0742, P0842, P0843, P0973, P0974, P0976, P0977, P1120, P1121, P1122, P1125, P1280, P1281, P1282, P1283, P1285, P1286, P1287, or P1288 are not set.
    • The ignition voltage is between 8 and 18 volts.
    • The engine speed is between 500 and 6,500 RPM for 5 seconds.
    • The transmission fluid temperature (TFT) is between 20-130°C (68-266°F).
    • The engine torque is between 50-1,492 N·m (37-1,100 lb ft).
    • The calc. throttle position is 8 percent or greater.
    • The transmission input speed sensor (ISS) is between 150-6,500 RPM.
    • The transmission output speed sensor (OSS) is 64 RPM or greater.
    • The time since the last gear change is 1 second.

Conditions for Setting the DTC

P0741

The TCC slip speed is 125 RPM or greater for 4 seconds, twice during the same ignition cycle.

P0751

The following conditions occur twice in 1 trip:

Condition 1

The TCM commands 1st gear and the gear ratio indicated 2nd gear, 1.54:1-1.71:1, for 2 seconds.

Condition 2

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

P0756

The following conditions occur twice in 1 trip:

Condition 1

The TCM commands 1st gear with the engine torque between 50-1,492 N·m (37-1,100 lb ft) and the gear ratio indicates 2nd gear, 1.54:1-1.71:1, for 2 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.

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

Component Connector End Views

Electrical Information Reference

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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References

Circuit/System Testing
  1. Perform the Transmission Fluid Check.
    2. ⇒Correct the transmission fluid level if the fluid is not at the proper level.
  2. 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 125 RPM.
    3. ⇒If the TCC Slip Speed is greater than 125 RPM, inspect the following components and repair or replace as necessary:
    • The cooling system for plugging
    • The cooling lines may be pinched
    • 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
    • The TCC blowoff valve or spring for damage or not seating
    • The TCC signal orifice in the spacer plate plugged
    • The #1 check ball missing or leaking
    • The spacer plate gaskets torn or leaking
    • The turbine shaft seals for leaks
    • The torque converter clutch
  3. 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.
    4. ⇒If the gear ratios do not match the commanded gear, inspect the following and repair or replace as necessary:

    P0751

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

    P0756

    • The 2-3 shift solenoid mechanically stuck
    • 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.
  2. 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 solenoid.
    3. ⇒If the resistance is not within the specified range, replace the affected solenoid.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.