P0751

DIAGNOSTIC TROUBLE CODE (DTC) P0751 1-2 SHIFT SOLENOID PERFORMANCE





Circuit Description
The 1-2 Shift Solenoid Valve (1-2 SS Valve) is used to control fluid flow acting on the 1-2 shift valve. The solenoid is a normally open valve that is used in conjunction with the 2-3 Shift Solenoid Valve (2-3 SS Valve) to allow four different shifting combinations (Refer to Shift Solenoid Chart). The solenoid is attached to the valve body within the transmission. Voltage is supplied directly to the solenoid through the Powertrain Control Module (PCM). The PCM commands the solenoid ON or OFF by providing a ground path through circuit 500.
The PCM monitors the actual gear ratio, and compares the actual gear ratio with the commanded gear ratio. Diagnostic Trouble Code (DTC) P0751 sets under four conditions.
- A stuck ON 1-2 SS Valve.
- A stuck OFF 1-2 SS Valve.
- A stuck ON 1-2 shift Valve.
- A stuck OFF 1-2 shift Valve.

Conditions For Setting The DTC
- No Input Speed Sensor (ISS) DTCs P0716 or P0717.
- No Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) DTC P1810.
- No Throttle Position (TP) Sensor DTC P1791.
- No Vehicle Speed Sensor (VSS) DTCs P0722 or P0723.
- Engine running.
- Manifold Air Pressure (MAP) is greater than 10 kPa.
- Transmission not in Park, Neutral or Reverse.
- Transmission Fluid Temperature (TFT) is greater than 20°C (68°F).
- Vehicle speed above 8 km/h (5 mph).
- TPS is greater than 8%.
All the above conditions are true and any one of the following conditions occur:
- PCM commands 1st gear and 2nd gear ratio between 1.54 - 1.71 is detected for 2 seconds.
- PCM commands 2nd gear and 1st gear ratio between 2.87 - 3.13 is detected for 4 seconds.
- PCM commands 3rd gear and 4th gear ratio between 0.67 - 0.72 is detected for 5 seconds.
- PCM commands 4th gear and 3rd gear ratio between 0.93 - 1.05 is detected for 5 seconds.

Action Taken When The DTC Is Set
- PCM will illuminate the Malfunction Indicator Lamp (MIL) after two consecutive trips with a failure reported.
- Freeze shift adapts from being updated.
- PCM inhibits Torque Converter Clutch (TCC) engagement.
- PCM commands maximum line pressure.
- PCM commands soft landing to 2nd gear.
- DTC P0751 will be stored in PCM memory.

Conditions For Clearing The DTC
- The PCM will turn the MIL off after DTC P0751 passes condition test. This DTC passes when all conditions for setting the DTC are met and the gear ratio matches the commanded gear for three consecutive ignition cycles.
- History DTC scan be cleared by using a Scan Tool.

Diagnostic Aids
- If the DTC cannot be reset after clearing the code, check for possible fluid contamination, plugged or restricted oil circuit.
- Inspect the wiring for poor electrical connections at the PCM and at the transmission 20-way connector. Look for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension as well. Also check for chafed wires that could short to bare metal or other wiring. Inspect for broken wire inside the insulation.
- If diagnosing for a possible intermittent short or open condition, move or massage the wiring harness while observing test equipment for a change.





Shift Solenoid Status Chart

















DTC P0751 - 1-2 Shift Solenoid Performance