P0781

Diagnostic Chart:

Wiring Diagram:

When a gear is commanded, the vehicle speed to turbine shaft speed ratio is monitored to assure the correct gear ratio. Second gear stuck on indicates that 1st gear was commanded but the actual ratio driving the vehicle is equal to 2nd gear. This is a calculated value TSS rpm/VSS rpm speed (turbine shaft speed sensor/vehicle speed sensor = gear ratio). Second gear clutch is turned Off by grounding circuit 1222 at the PCM.

DTC PARAMETERS

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

- 1st gear commanded by PCM.

- No noise detected on turbine shaft or vehicle speed signals.

- Vehicle speed greater than 5 km/h (3 mph).

- Turbine shaft speed greater than 224 rpm.

- Speed ratio across the torque converter, engine speed versus turbine speed, less than 180. A speed ratio of 255 would be TCC on.

- PCM calculated engine load value is greater than 200.

- The ratio of turbine shaft speed to vehicle speed equals that of 2nd gear.

TEST DESCRIPTION

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

2. Check actuator operation. Use actuator quick check. Listen and compare noise of 2nd gear actuator to that of other actuators. The noise of all should be similar. Actuator Quick Chart

NOTE: To check actuator operation, command actuator quick test using the Scan tool.

3. Perform 2nd clutch air check. Apply compressed air with rubber nozzle on air gun. Problem could be a mechanical failure. This step begins internal diagnosis.

4. Cross leaks to/from 2nd clutch circuit can cause 2nd clutch to be on at all times. If DTC P0781 is present and there is no reverse, check end cover input hub seals.

5. As air pressure is applied and released, the clutch plates should also apply and release. If clutch plates are moving normally and no other leaks detected, the problem is probably in the valvebody. If clutches are not moving correctly, the problem is in the end cover or an internal clutch assembly problem.

REPAIR VERIFICATION

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

Criteria for pass:

- Engine running.

- Power present at actuators and no active faults exist for this actuator.

DIAGNOSTIC AIDS

- When the PCM detects a fault in the circuit (open, ground, short), the PCM will open the circuit internally to protect the circuit.

- Could be a hot or cold only condition. If condition is intermittent, try to reproduce conditions in MALF table to reset the DTC.

- Problem could be internal. 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, actuator connector plate or Under Hood Junction Block (UHJB) terminals. Wiggling connectors while performing an actuator quick test may help isolate the problem area.