Chevrolet Trax: DTC P0751 OR P0752

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

NOTE: The DTCs listed below set due to a transmission hydraulic/mechanical condition. Perform the Circuit/System Verification and Circuit/System Testing to identify the cause.

DTC P0751

Shift Solenoid Valve 1 Performance - Stuck Off - Transmission Hydraulic/Mechanical Performance

DTC P0752

Shift Solenoid Valve 1 Performance - Stuck On - Transmission Hydraulic/Mechanical Performance

Circuit/System Description

Shift solenoid valve 1 is part of the control solenoid valve assembly, which has no serviceable components. The solenoid valve operates by the transmission control module (TCM) turning the low side driver ON or OFF.

When the shift solenoid valve 1 is commanded OFF, the plunger forces the metering ball against the actuator feed limit seat, blocking the flow and any existing pressure is exhausted through the exhaust port. When the shift solenoid valve 1 is commanded ON, the internal plunger moves, allowing the metering valve to move away from the actuator feed limit seat and against the exhaust seat, creating signal fluid pressure. The signal fluid pressure acts against the clutch select valve 2 to overcome the valve spring force, moving the valve to the apply position. Fluid pressure from the R1/4-5-6 regulator valve flows through clutch select valve 2 and is directed to either the low and reverse clutch or the 4-5-6 clutch, depending on the position of clutch select valve 2.

Conditions for Running the DTC

• DTC P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0716, P0717, P0722, P0723, or P182E is not set.
• Transmission fluid temperature is -6.6ºC (20ºF) or greater.
• Engine speed is between 400-7,500 RPM for 5 s.
• Output shaft speed is 100 RPM or greater, or the throttle position is 0.5% or greater.
• Ignition voltage is 9-32 V.
• Shift is complete.
• Engine torque signal is valid.
• Throttle position signal is valid.
• High-Side driver is enabled.
• DTC runs continuously when above conditions are met.

Conditions for Setting the DTC

P0751

• Commanded gear is 1st.
• TCM detects gear ratio 1.37-1.52.
• Gearbox slip is 400 RPM or greater for 2 s.
• Conditions listed above have to occur 8 times.

P0752

• Commanded gear is 3rd.
• Transmission has achieved 1st or 2nd.
• Gear slip is 400 RPM or greater for 1.5 s.
• TCM commands 4th gear if above conditions exist and detects a gear ratio of 4.35-4.81 for 1.5 s.
• Conditions listed above have to occur 5 times.

Action Taken When the DTC Sets

P0751

• P0751 is a type B DTC.
• TCM inhibits 1st gear.
• TCM inhibits Neutral idle.

P0752

• P0752 is a type A DTC.
• TCM limits the transmission to 2nd range and reverse.
• TCM inhibits Tap Up/Down function.
• TCM inhibits manual shifting of forward gears.
• TCM inhibits auto grade braking.
• TCM disables neutral idle.
• TCM freezes adapts.
• TCM commands maximum line pressure.
• TCM commands 2nd gear if transmission is in a forward range and the output speed is less than 1350 RPM, or neutral if the output speed is 1350 RPM or greater.

Conditions for Clearing the DTC

• P0751 is a type B DTC.
• P0752 is a type A DTC.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics (Encore, MH8 or MHB) , Automatic Transmission Controls Schematics (Trax, MH8 or MHB)

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - ENCORE WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - TRAX

• Inline Harness Connector End Views (Encore) , Inline Harness Connector End Views (Trax)

Description and Operation

• Drive Range, First Gear Engine Braking (Gen 2/Hybrid)
• Drive Range, Third Gear (Gen 2/Hybrid)
• Electronic Component Description
• Transmission Component and System Description
• Transmission General Description

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (LUV) , Powertrain Diagnostic Trouble Code (DTC) Type Definitions (2H0)

Scan Tool Reference

Control Module References for scan tool information

Special Tools

DT-48616 Solenoid Assembly Test Kit & Adapter Harness

For equivalent regional tools, refer to Special Tools

Circuit/System Verification

NOTE: If other DTCs are set, diagnose those DTCs first.

1. Ignition ON, engine OFF.
2. Verify no other TCM DTCs are set using a scan tool.

If another DTC is set

Refer to Diagnostic Trouble Code (DTC) List - Vehicle .

If no other DTCs are set

3. Engine idling at the normal operating temperature, transmission in Park, with parking brake applied and drive wheels chocked.
4. Verify the transmission fluid level and condition is correct. Refer to Transmission Fluid Level and Condition Check.

If the transmission fluid level and condition is not correct

Repair as necessary.

If the transmission fluid level and condition is correct

5. Ignition ON, clear the TCM DTCs with a scan tool.
6. From a stop, accelerate to 72 km/h (45 mph) with the Calculated Throttle Position greater than 15%.

   Perform this test 8 times.

7. Verify DTC P0751 or P0752 did not set.

If DTC P0751 or P0752 sets

Refer to Circuit/System Testing.

If DTC P0751 or P0752 does not set

8. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
9. Verify the DTC does not set.

If the DTC sets

Refer to Circuit/System Testing.

If the DTC does not set

10. All OK.

Circuit/System Testing

WARNING: Refer to Parking Brake and Drive Wheels Warning .

NOTE: You must perform the Circuit/System Verification first.

1. Engine idling at the normal operating temperature.
2. Verify the transmission line pressures are within the specified range. Refer to Line Pressure Check, and Solenoid Valve Pressure (Gen 2) .

If the pressures are not within range

Refer to Fluid Pressure High or Low.

If the pressures are within range

3. Ignition OFF, remove the Q8 Control Solenoid Valve Assembly.
4. Verify the pressure changes for all solenoids when performing the solenoid test. Refer to Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test.

If the pressure does not change

Replace the Q8 Control Solenoid Valve Assembly.

If the pressure changes

5. Verify the mechanical conditions listed below do not exist. Repair or replace as necessary.

P0751 - Control Valve Body

• Clutch select valve bore plug undersized. Plug should be a valve fit in the bore.
• Check ball #1 missing, damaged/malformed.
• Seat for check ball #1 damaged or leaking.

P0751 or P0752 - Control Valve Body

• Clutch select valve stuck from debris, sediment, binding, or a scored bore.
• Low and reverse and 4-5-6 clutch regulator valve stuck or sticking from debris, sediment, binding, or a scored bore.

P0751 or P0752 - Channel Plate and Spacer Plate

Oil channels or orifices blocked by debris.

P0751 or P0752 - Q8 Control Solenoid Valve Assembly

• Not pressurizing due to shift solenoid valve 1 being stuck OFF or leaking.
• Pressure not exhausting due to shift solenoid valve 1 being stuck ON.
• Control signal fluid supply leak due to valve body filter plate assembly cracked, blocked, or damaged gasket seal.

P0752 Output Carrier Assembly

Output carrier pinion pins too high or too low.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Perform the Transmission Adaptive Values Learn following all transmission repairs
• Control Module References - for Control Solenoid Valve Assembly replacement, programming and setup

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