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 P0751: 1-2 Shift solenoid (SS) Valve Performance - No First or Fourth GearDTC P0752: 1-2 Shift solenoid (SS) Valve Performance - No Second or Third Gear
Diagnostic Fault Information
Hydraulic Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
1-2 SS Valve | -- | -- | -- | P0751, P0752 |
2-3 SS Valve | -- | -- | -- | P0756, P0757 |
TCC PWM Valve | -- | -- | -- | P0741, P0742 |
Typical Scan Tool Data
Circuit | Normal | Short to Ground | Open/High Resistance | Short to Voltage |
|---|---|---|---|---|
Operating Conditions: Engine running, normal operating temperature Parameter Normal Range: OK | ||||
1-2 Sol. CKT Status | OK | Open/Short to GND | Open/Short to GND | Short to Volts |
2-3 Sol. CKT Status | OK | Open/Short to GND | Open/Short to GND | Short to Volts |
TCC Duty Cycle CKT Status | OK | Open/Short to GND | Open/Short to GND | Short to Volts |
Circuit/System Description
The 1-2 shift solenoid (SS) valve and the 2-3 SS valve are supplied with fused ignition voltage. The ground path is controlled by the transmission control module (TCM). When the TCM 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 TCM commands the solenoid ON, a ground path is provided and the exhaust port is blocked, stopping the exhaust of line pressure. The TCM identifies a 1-2 SS valve or a 2-3 SS valve condition by monitoring the commanded gear versus gear ratio. Refer to Shift Solenoid Valve State and Gear Ratio .
Conditions for Running the DTC
P0751
| • | No TP sensor DTCs P0121, P0122, or P0123. |
| • | No ISS DTCs P0716 or P0717. |
| • | No OSS DTCs P0722 or P0723. |
| • | No TCC system stuck ON DTC P0742. |
| • | No 1-2 SS valve electrical DTCs P0973 or P0974. |
| • | No 2-3 SS valve electrical DTCs P0976 or P0977. |
| • | The calc. throttle position is 8 percent or more. |
| • | The transmission ISS is 150 RPM or more. |
| • | The transmission OSS is 200 RPM or more. |
| • | The time since the last gear change is 1 second. |
| • | The engine speed is greater than 500 RPM for 5 seconds. |
| • | The transmission fluid temperature is between 20-130°C (68-266°F). |
| • | The engine torque is greater than 50 N·m (37 lb ft). |
P0752
| • | No TP sensor DTCs P0121, P0122, or P0123. |
| • | No ISS DTCs P0716 or P0717. |
| • | No OSS DTCs P0722 or P0723. |
| • | No TCC system stuck ON DTC P0742. |
| • | No 1-2 SS valve electrical DTCs P0973 or P0974. |
| • | No 2-3 SS valve electrical DTCs P0976 or P0977. |
| • | The calc. throttle position is 8 percent or more. |
| • | The transmission ISS is 150 RPM or more. |
| • | The transmission OSS is 200 RPM or more. |
| • | The engine torque is greater than 50 N·m (37 lb ft). |
| • | The time since the last gear change is 1 second. |
| • | The engine speed is greater than 500 RPM for 5 seconds. |
| • | The transmission fluid temperature is between 20-130°C (68-266°F). |
Conditions for Setting the DTC
P0751
The following conditions both occur twice in one trip:
P0751 - Condition 1
The TCM commands 1st gear and the gear ratio indicates 2nd gear, 1.54:1 to 1.71:1. for 2 seconds.
P0751 - Condition 2
The TCM commands 4th gear and the gear ratio indicates 3rd gear, 0.95:1 to 1.05:1, for 4 seconds.
P0752
The following conditions both occur twice in one trip:
P0752 - Condition 1
The TCM commands 2nd gear and the gear ratio indicates 1st gear, 2.81:1 to 3.11:1 for 2 seconds.
P0752 - Condition 2
The TCM commands 3rd gear and the gear ratio indicates 4th gear, 0.65:1 to 0.72:1, for 3 seconds.
Action Taken When the DTC Sets
P0751
| • | DTC P0751 is a Type B DTC. |
| • | The TCM commands maximum line pressure. |
| • | The TCM disables TAP shift operation, if equipped. |
| • | The TCM freezes transmission adaptive functions. |
| • | The TCM commands an alternate coast shift pattern where downshifts occur at higher vehicle speeds while coasting. |
P0752
| • | DTC P0752 is a Type B DTC. |
| • | The TCM inhibits 3-2 downshifts when the vehicle speed is greater than 52 km/h (32 mph). |
| • | The TCM forces the TCC ON. |
| • | The TCM commands maximum line pressure. |
| • | The TCM freezes transmission adaptive functions. |
Conditions for Clearing the DTC
DTCs P0751 and P0752 are Type B DTCs.
Diagnostic Aids
If the DTC is cleared, then will not reset when the vehicle is driven, some of the following conditions may exist:
| • | Fluid contamination |
| • | Plugged fluid circuits |
| • | Restricted fluid circuits |
| • | Inspect transmission fluid lines to radiator. Lines may be pinched, plugged or twisted. |
| • | Refer to Shift Solenoid Valve State and Gear Ratio . |
| • | Internal damage to the torque converter may prevent TCC application. |
| • | It is possible for an internal TCM failure which may not allow sufficient current to operate the solenoids. Verify TCM functionality by commanding the suspected solenoid ON/OFF using the scan tool and listen for a click. |
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Perform the Transmission Fluid Check to verify correct fluid level and condition. The transmission fluid level should be within the crosshatch band and the transmission fluid should be red or dark brown.
- Operate the vehicle in Drive and ensure that the TCM commands all gears. The ratios should match the commanded gear for all gears. Refer to Shift Solenoid Valve State and Gear Ratio .
- 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.
| ⇒ | If the transmission fluid is low or discolored, refer to Automatic Transmission Fluid Filter and Seal Replacement . |
| ⇒ | If the gear ratios do not match the commanded gear, inspect the following and repair/replace as necessary: |
| • | Inspect the shift solenoid/hydraulic circuit for an internal malfunction. |
| • | Damaged seals on the shift solenoid valve. Refer to Shift Solenoid Leak Test for further diagnosis. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
