Circuit Description
The 1-2 shift solenoid (SS) valve controls the fluid flow acting on the 1-2 and 3-4 shift valves. The 1-2 SS valve is a normally-open exhaust valve that is used with the 2-3 SS valve, in order to allow 4 different shifting combinations.
When the powertrain control module (PCM) detects a 2-2-3-3 shift pattern, then DTC P0751 sets. DTC P0751 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0751 1-2 Shift Solenoid Valve Performance - No First or Fourth Gear
Conditions for Running the DTC
| • | No vehicle speed sensor (VSS) DTCs P0502 or P0503. |
| • | No 1-2 SS valve DTC P0973 or P0974. |
| • | No 2-3 SS valve DTC P0976 or P0977. |
| • | No transmission fluid pressure (TFP) manual valve position switch DTC P1810, P1815 or P1816. |
| • | The engine speed is greater than 475 RPM for 5 seconds. |
| • | The gear range is D4, D3, D2 or D1. |
| • | The throttle position (TP) angle is greater than 25 percent. |
| • | The transmission fluid temperature is 20-130°C (68-266°F). |
| • | The engine torque is 55-550 N·m (40-405 lb ft). |
| • | The vehicle speed is greater than 2 km/h (1 mph). |
Conditions for Setting the DTC
DTC P0751 sets if both of the following conditions occur twice:
Condition 1
| • | The PCM commands first gear for 2 seconds. |
| • | The estimated gear ratio is 1.2-1.825. |
| • | All conditions are met for 1.5 seconds. |
Condition 2
| • | The PCM commands fourth gear for 1 second. |
| • | The estimated gear ratio is 0.95-1.15. |
| • | All conditions are met for 6 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met. |
| • | The PCM commands D2 line pressure. |
| • | The PCM commands TCC OFF. |
| • | The PCM inhibits fourth gear in hot mode. |
| • | The PCM freezes transmission adapt functions. |
| • | The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records. |
| • | 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 can clear the MIL/DTC. |
| • | The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring. |
| • | The PCM cancels the DTC default actions when the fault no longer exists and/or 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 the Shift Solenoid Valve State and Gear Ratio table. |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||
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 powertrain control module (PCM). Accelerate 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 Testing for Intermittent Conditions and Poor Connections | |||||
3 | Inspect the shift solenoid/hydraulic circuit for the following conditions:
Refer to Shift Solenoid Leak Test . Did you find and correct the condition? | -- | Go to Step 4 | -- | ||||
4 | Perform the following procedure in order to verify the repair:
Hold the throttle at 20 percent and accelerate to 88 km/h (55 mph). Has the test run and passed? | -- | Go to Step 5 | Go to Step 2 | ||||
5 | 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? | -- | System OK |
