Circuit Description
The 1-2 shift solenoid valve (1-2 SS Valve) is fed ignition voltage
by circuit 1039 and the ground path is provided by the powertrain control
module (PCM), depending on the solenoids commanded state. When the PCM 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 PCM commands the solenoid
ON, a ground path is provided and the exhaust port is blocked, stopping
the exhaust of line pressure.
The PCM identifies a 1-2 SS Valve condition by monitoring the commanded
gear versus gear ratio.
If the PCM detects a gear ratio that is outside its limits for a particular
commanded gear, then DTC P0751 sets. DTC P0751 is a Type B DTC.
Conditions for Setting the DTC
DTC P0751 sets during the second consecutive trip in which the following
conditions occur:
| • | No TP sensor DTCs P0121, P0122 or P0123 are set. |
| • | No VSS DTCs P0502 or P0503 are set. |
| • | No A/T ISS sensor DTCs P0716 or P0717 are set. |
| • | No 1-2 shift solenoid valve electrical DTC P0753 is set. |
| • | No 2-3 shift solenoid valve electrical DTC P0758 is set. |
| • | No TFP Valve Position Switch DTC P1810 is set. |
| • | No TCC PWM Solenoid Valve DTC P1860 is set. |
| • | The engine speed is greater than 500 RPM for 5 seconds
and not in fuel shut off. |
| • | The transmission is not in PARK or NEUTRAL. |
| • | The vehicle speed is greater than 8 km/h (5 mph). |
| • | The throttle position angle is greater than 10%. |
| • | The transmission fluid temperature is greater than 20°C (68°F). |
| • | The engine torque is 70-270 N·m (50-200 lb ft). |
All of the above conditions are met and Cases 1 and 4 are true twice,
or Cases 2 and 3 are true twice.
Case 1
| • | First gear is commanded. |
| • | The gear ratio indicates second gear (1.52:1 to 1.62:1). |
| • | Condition is met for 2 seconds. |
Case 2
| • | Second gear is commanded. |
| • | The gear ratio indicates first gear (2.87:1 to 2.97:1). |
| • | Condition is met for 3 seconds. |
Case 3
| • | Third gear is commanded. |
| • | The gear ratio indicates fourth gear (0.65:1 to 0.75:1). |
| • | Condition is met for 3 seconds. |
Case 4
| • | Fourth gear is commanded. |
| • | The gear ratio indicates third gear (0.95:1 to 1.05:1). |
| • | Condition is met for 3 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the Malfunction Indicator Lamp (MIL). |
| • | The PCM commands maximum line pressure. |
| • | The PCM freezes shift adapts. |
| • | The PCM inhibits 3-2 downshifts when the vehicle speed is greater
than 48 km/h (30 mph). |
| • | The PCM stores DTC P0751 in PCM history. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the MIL during the third consecutive trip in
which the diagnostic test runs and passes. |
| • | A scan tool clears the DTC from the PCM history. |
| • | The PCM clears the DTC from the PCM history if the vehicle completes
40 consecutive warm-up cycles without an 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
| • | Inspect the transmission fluid for sediment. |
| • | Inspect the transmission filter for debris. |
Test Description
Important: Do not drive the vehicle for an extended period of time because additional
internal damage may occur.
The numbers below refer to the step numbers on the diagnostic table.
-
This step replaces the 1-2 shift solenoid valve if no hydraulic or mechanical
condition is found.
DTC P0751 1-2 Shift Solenoid Valve -- Performance
Step
| Action
| Value(s)
| Yes
| No
|
1
| Was the Powertrain On-Board Diagnostic (OBD) System Check
performed?
| --
|
Go to Step
2
| Go to
Powertrain On Board Diagnostic (OBD) System Check
in Engine Controls
|
2
| Was the transmission fluid checking procedure performed?
| --
|
Go to Step
3
| Go to
Transmission Fluid Check
|
3
|
- Install the Scan Tool
.
- 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. Using the Clear Info function will erase the stored Freeze Frame
and Failure Records from the PCM.
- Record the DTC Freeze Frame and Failure Records.
- Clear the DTCs.
- Inspect for the following conditions:
| • | 1-2 shift solenoid valve for sediment or debris. |
| • | 1-2 shift solenoid valve for a damaged or missing O-ring. |
| • | 1-2 shift valve for sediment or debris and the possibility of
a bent or stuck 1-2 shift valve. |
Refer to Unit Repair.
Was a condition found and corrected?
| --
|
Go to Step 5
|
Go to Step 4
|
4
| Replace the 1-2 shift solenoid valve.
Refer to
1-2 Shift Solenoid Valve Replacement
.
Is the replacement complete?
| --
|
Go to Step 5
| --
|
5
| Perform
the following procedure in order to verify the repair:
- Select DTC.
- Select Clear Info.
- Operate the vehicle under the following conditions:
| • | The transmission fluid temperature greater than 20°C (68°F). |
| • | The engine speed more than 500 RPM for 5 seconds
and not in fuel shut off. |
| • | The throttle position angle greater than 10%. |
| • | The gear range not in PARK or NEUTRAL. |
| • | The vehicle speed more than 8 km/h (5 mph). |
| • | The engine torque is 70-270 N·m (50-200 lb ft). |
| • | Each of the following pass criteria must be true for 1 second: |
Case 1
| - | The gear ratio is 2.87:1 to 2.97:1. |
Case 2
| - | The gear ratio is 1.52:1 to 1.62:1. |
Case 3
| - | The gear ratio is 0.95:1 to 1.05:1 |
Case 4
| - | The gear ratio is 0.65:1 to 0.75:1. |
- Select Specific DTC. Enter DTC P0751.
Has the test run and passed?
| --
| System OK
|
Go to Step 1
|
