DTC P0781

Circuit Description

Click here for detailed picture of above image.

When a gear is commanded ON, the vehicle speed to input shaft speed ratio is monitored to assure the correct gear ratio. Shift solenoid 2 performance indicates that 1st gear was commanded ON, but the actual ratio driving the vehicle is equal to 2nd gear. This is calculated value ISS RPM/VSS RPM speed. The input shaft speed sensor/vehicle speed sensor equals gear ratio. Second gear clutch is turned OFF by grounding circuit 1222 at the PCM.

Conditions for Setting the DTC

DTC P0781 is set when the PCM has seen the following conditions for more than 3 seconds twice per ignition cycle:

First gear is commanded by the PCM.
No noise is detected on the input shaft or vehicle speed signals.
Vehicle speed is greater than 5 km/h (3 mph).
Input shaft speed is greater than 224 RPM.
The speed ratio across the torque converter, engine speed versus input speed, is less than 180. A speed ratio of 255 would be TCC on.
The PCM calculated engine load value is greater than 200.
The ratio of input shaft speed to vehicle speed equals that of 2nd gear.

Test Description

Check for DTCs P0740, P0756, P0758, or P0759. They must be eliminated first as a possible cause of DTC P0781.

Important

To check the solenoid operation, command the solenoid quick test using the scan tool.

Check the solenoid operation. Use the solenoid quick check in the test section. Listen and compare the noise of the 2nd gear solenoid to that of the other solenoids. The noise of all should be similar.
Perform the 2nd clutch air check. For pressure apply points, refer to Test Section Diagnosis. Apply compressed air with the rubber nozzle on the air gun. The problem could be a mechanical failure. This step begins the internal diagnosis.
Cross leaks to and from the 2nd clutch circuit can cause the 2nd clutch to be on at all times. If DTC P0781 is present and there is no reverse, check the end cover input hub seals.
As air pressure is applied and released, the clutch plates should also apply and release. If the clutch plates are moving normally and no other leaks are detected, the problem is probably in the valvebody. If the clutches are not moving correctly, the problem is in the end cover or an internal clutch assembly problem.

Repair Verification

Monitor the DTC menu Code Status for Pass Since Code Clear and Pass This Ignition Cycle. When both have passed, the repair is verified.

Criteria for pass:

The engine is running.
Power is present at the solenoids and no active faults exist for this solenoid.

Diagnostic Aids

When the PCM detects a fault in the circuit, an open, ground, or short, the PCM will open the circuit internally to protect the circuit.
This could be a hot or cold only condition. If the condition is intermittent, try to reproduce the conditions in the MALF table to reset the DTC.
The problem could be internal. There is a possible hydraulic leak, seals, gaskets, porosity, etc.
This DTC may set or intermittent 2nd gear starts may be caused by a poor electrical connection at either the PCM, solenoid connector plate, or UHJB terminals. Wiggling the connectors while performing a solenoid quick test may help isolate the problem area.