DTC P0751. GMC Truck GMC C Sierra

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2004 🢒 GMC C Sierra - 2WD 🢒 Engine 🢒 Engine Controls - 4.8L, 5.3L, and 6.0L 🢒 DTC P0751

Master Electrical Component List
Automatic Transmission Controls Schematics

Circuit Description

The 1-2 shift solenoid (SS) valve controls the fluid flow action on the 1-2 and the 3-4 shift valves. The 1-2 SS valve is a normally-open exhaust valve that is used with the 2-3 SS in order to allow four different shifting combinations.

When the powertrain control module (PCM) detects a 2-2-3-3 gear ratio, then DTC P0751 sets. DTC P0751 is a type C DTC. For California emissions vehicles and vehicles under 8,600 GVW, DTC P0751 is a type B DTC.

Conditions for Running the DTC

•	No MAP sensor DTCs P0106, P0107, or P0108.

•	No shift solenoid electrical DTCs P0753 or P0758.

•	No TP sensor DTCs P0121, P0122, or P0123.

•	No TCC Stuck On DTC P0742.

•	No ISS sensor DTCs P0716 or P0717.

•	Not in 4WD Low.

•	No VSS DTCs P0502 or P0503.

•	No TFP manual valve position switch DTC P1810.

•	No TCC PWM solenoid valve DTC P2761.

•	No MAF sensor DTC P0101, P0102, or P0103.

•	No TCC Stuck Off DTC P0741.

•	No transmission component slipping DTC P0894.

•	The engine vacuum is 0-105 kPa.

•	The system voltage is 10-18 volts.

•	Transmission OSS is greater than 7 RPM.

•	Transmission ISS is greater than 7 RPM.

•	The TP sensor is greater than 10 percent.

•	The engine torque must be 108-576 N·m (80-425 lb ft).

•	No TFP manual valve position switch change within 6 seconds.

•	The TFP manual valve position switch indicates D4.

•	The transmission fluid temperature (TFT) is greater than 20°C (68°F) and less than 130°C (266°F).

Conditions for Setting the DTC

•	The commanded gear equals 1st and the ratio equals 2nd for greater than 2 seconds.

•	The commanded gear equals 4th with the TCC locked and the ratio equals 3rd for greater than 3.75 seconds.

•	All conditions are met for 2 occurrences.

Action Taken When the DTC Sets

•	For California emission equipped vehicles, the PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met. For Federal emission equipped vehicles, the MIL is not illuminated.

•	The PCM commands maximum line pressure.

•	The PCM freezes shift adapts.

•	The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame, California only, and Failure Records, California and Federal.

•	The PCM stores the DTC P0751 in PCM history during the second consecutive trip, California, or the first trip, Federal, in which the Conditions for Setting the DTC are met.

Conditions for Clearing the MIL/DTC

•	For California emissions, the PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.

•	A scan tool can clear the MIL/DTC.

•	For California emissions, the PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission related diagnostic fault occurring.

•	For Federal emissions, the PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission related diagnostic fault occurring.

•	The PCM cancels the DTC default actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the PCM.

Diagnostic Aids

•	Verify that the transmission meets the specifications in the Shift Speed table. Refer to Shift Speed .

•	Other internal transmission failures may cause incorrect gear ratios to occur. Refer to Shift Solenoid Valve State and Gear Ratio .

•	DTC P0751 defaults to an elevated line pressure condition which may result in partial TCC apply. This may produce an idle surge that could stall the engine.

Test Description

The number below refers to the step number on the diagnostic table.

This step tests that the PCM commanded all shifts, that all shift solenoid valves responded correctly, but that all the shifts did not occur.

Step

Action

Value(s)

Yes

Did you perform the Diagnostic System Check - Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls in Engine Controls - 4.8L, 5.3L, and 6.0L

Install a scan tool.
Turn ON the ignition, with the engine OFF.

Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the PCM.

Record the DTC Freeze Frame and Failure Records.
Clear the DTC.
Drive the vehicle in D4 range, accelerating the vehicle, ensuring that the PCM commands 1st, 2nd, 3rd and 4th gears.

Did you detect a 2-2-3-3 shift pattern?

Go to Step 3

Go to Intermittent Conditions in Engine Controls - 4.8L, 5.3L, and 6.0L

Inspect the shift solenoid/hydraulic circuit for the following conditions:

•	1-2 shift solenoid mechanically stuck OFF

•	Refer to Shift Solenoid Leak Test .

•	1-2 shift valve stuck in the released position

•	Damaged seals on the 1-2 shift solenoid valves

•	Refer to Shift Solenoid Leak Test .

Clean and inspect the related valves, bores and the valve body for debris or contamination restricting valve movement.

Refer to Control Valve Body Cleaning and Inspection in Transmission Unit Repair Manual.

Did you find and correct the condition?

Go to Step 4

Perform the following procedure in order to verify the repair:

Select DTC.
Select Clear Info.
Drive the vehicle in D4 range, holding the throttle at 40% and accelerating to 89 km/h (55 mph), only if traffic and road conditions permit.
Select Specific DTC.
Enter DTC P0751.

Has the test run and passed?

Go to Step 5

Go to Step 2

With the scan tool, observe the stored information, capture info and DTC info.

Does the scan tool display any DTCs that you have not diagnosed?

Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 4.8L, 5.3L, and 6.0L

System OK