DTC P0751 1-2 Shift Solenoid Valve Performance. GMC Truck Safari

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 1997 🢒 Safari - 2WD 🢒 Transmission/Transaxle 🢒 Automatic Transmission - 4L60-E 🢒 DTC P0751 1-2 Shift Solenoid Valve Performance

Table 1:	Shift Solenoid Valve State and Gear Ratio 4L60-E
Table 2:	DTC P0751 1-2 Shift Solenoid Valve (1-2 SS Valve) -- Performance

Automatic Transmission Components
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice

Circuit Description

The 1-2 Shift Solenoid Valve (1-2 SS Valve) controls the fluid flow acting on the 1-2 and 3-4 shift valves. The solenoid is a normally-open exhaust valve. With the 2-3 Shift Solenoid Valve (2-3 SS Valve), the 1-2 SS Valve allows four different shifting combinations.

When the VCM detects a 1-1-4-4 only or a 2-2-3-3 only shift pattern, depending on the state of the mechanical failure, then DTC P0751 sets. DTC P0751 is a type A DTC.

Conditions for Setting the DTC

•	No TP DTCs P0122 or P0123

•	No VSS Assy. DTC P0502

•	No TCC Sol. Valve DTC P0740

•	No TCC Stuck ON DTC P0742

•	No 1-2 SS Valve DTC P0753

•	No 2-3 SS Valve DTC P0758

•	No 3-2 SS Valve Assy. DTC P0785

•	No TFP Val. Position Sw. DTC P1810

•	No TCC PWM Sol. Valve DTC P1860

•	The gear range is D4.

•	The vehicle speed is greater than 8 km/h (5 mph).

•	The engine speed is greater than 450 RPM for 8 seconds.

•	The transmission fluid temperature is 20-130°C (68-266°F).

•	Not in fuel cutoff

All the above conditions are met three times and the combination of Cases 1,2,3, and 4 or Cases 1,2,3, and 5 occurs three times:

Case 1

•	The VCM commands a 1-2 shift.

•	The TP angle is 18-45%.

•	The TP angle is constant within +/- 6%.

•	The vehicle speed is 8-56 km/h (5-35 mph).

•	Within 2 seconds, the engine speed in 2nd gear is 100 RPM greater than the last speed in 1st gear.

Case 2

•	The VCM commands a 2-3 shift

•	The TP angle is 10-45%.

•	The TP angle is constant within +/- 7%.

•	The vehicle speed is 32-80 km/h (20-50 mph).

•	Within 2 seconds, the engine speed in 3rd gear is 100 RPM less than the last speed in 2nd gear.

Case 3

•	The VCM commands a 3-4 shift.

•	The TP angle is 10-45%.

•	The TP angle is constant within +/- 7%.

•	The vehicle speed is 48-105 km/h (30-65 mph).

•	Within 2 seconds, the engine speed in 3rd gear is 20 RPM greater than the last speed in 4th gear.

Case 4

•	The VCM commands 4th gear.

•	The TCC is ON.

•	The TP angle is 8-35%.

•	The speed ratio is 0.85:1.2 (speed ratio is engine speed divided by output speed).

•	The TCC slip speed is 200-1000 RPM for 4 seconds.

Case 5

•	The VCM commands 4th gear.

•	The TCC is ON.

•	The TP is 8-35%.

•	The speed ratio is 0.6:0.8.

•	The TCC slip speed is -20 to +40 RPM for 4 seconds.

Action Taken When the DTC Sets

•	The VCM commands D2 line pressure.

•	The VCM freezes shift adapts from being updated.

•	The VCM illuminates the Malfunction Indicator Lamp (MIL).

Conditions for Clearing the MIL/DTC

•	The VCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.

•	A scan tool can clear the DTC from the VCM history. The VCM clears the DTC from the VCM history if the vehicle completes 40 warm-up cycles without a failure reported.

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

Diagnostic Aids

•	Verify that the transmission meets the specifications in the 4L60-E shift speed chart.

•	Other internal transmission failures may cause more than one shift to occur.

Shift Solenoid Valve State and Gear Ratio 4L60-E

Gear	1-2 Shift Solenoid	2-3 Shift Solenoid	Gear Ratio
1	ON	ON	3.059:1
2	OFF	ON	1.625:1
3	OFF	OFF	1.000:1
4	ON	OFF	0.696:1

Test Description

The numbers below refer to the step numbers on the diagnostic table.

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

DTC P0751 1-2 Shift Solenoid Valve (1-2 SS Valve) -- Performance

Step

Action

Value(s)

Yes

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Install the Scan Tool ®.
With the engine OFF, turn the ignition switch to the RUN position.

Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data.

Record the DTC Freeze Frame and Failure Records.
While the engine is operating, raise the drive wheels.
With the transmission in D4 range, use the scan tool to command 1st, 2nd, 3rd, and 4th gears while accelerating the vehicle.

Was a 1-1-4-4 or 2-2-3-3 only shift pattern detected? (Road testing the vehicle may be necessary.)

Go to Step 3

Go to Diagnostic Aids

Check the shift solenoid/hydraulic circuit for:

•	An internal malfunction.

•	Damaged seals on one or both of the shift solenoid valves.

•	Refer to the diagnosis tables.

Was a problem found and corrected?

Go to Step 4

In order to verify your repair, perform the following procedure:

Select DTC.
Select Clear Info.
Operate the vehicle under the following conditions (only if traffic and road conditions permit):

Hold the throttle at 20% and accelerate to 55 mph. If throttle moves more than 6%, stop the vehicle and start over.

Select Specific DTC. Enter DTC P0751.

Has the test run and passed?

System OK

Begin the diagnosis again. Go to Step 1