P0781
Diagnostic Chart:
The PCM uses the Crankshaft Position (CKP) sensor, Transaxle Input Speed Sensor (ISS) and Vehicle Speed Sensor (VSS) to determine engine speed, input shaft speed and output shaft speed. These sensor readings are used to determine the current gear ratio and RPM slip across the torque converter. The PCM uses this information from the sensors to determine if the commanded gear matches the actual gear. During normal driving conditions, the PCM will adapt main line pressure via the Pressure Control (PC) solenoid to prevent slipping and harsh shifts. Shift solenoid 2 is used to apply or release second gear clutch. The PCM controls 2nd gear by controlling the ground for shift solenoid 2. The PCM will turn the solenoid Off (open the driver circuit) when second gear is commanded On to apply 2nd clutch. Shift solenoid 2 is supplied ignition voltage from the fuel pump relay whenever the PCM commands the fuel pump relay On. DTC P0781 sets when 1st gear is being commanded On, and the ratio of the transaxle ISS to the VSS is within ±4% of 2nd gear. This indicates that 2nd gear is stuck On.
DTC PARAMETERS
DTC P0781 will set if the PCM detects 2nd gear ratio within ±4% when:
- 1st gear is being commanded On
- Condition exists for longer than 3 seconds
- Condition exists twice in one ignition cycle
- Transmission ISS is greater than 224 RPM
- Vehicle speed is greater than 5 km/h (3 mph)
- Speed noise parameter = NO
- TCC is commanded Off
- Engine torque is greater than 100 N.m (74 ft-lbs)
DTC P0781 diagnostic runs continuously once the above conditions have been met.
DTC P0781 is a type A DTC.
DIAGNOSTIC AIDS
IMPORTANT: If DTC P0756, P0758 or P0789 is set, diagnose that DTC first. A diagnosed shift solenoid 2 low/high circuit fault DTC may have caused DTC P0781 to set.
Refer to "Test Section Diagnosis" for pressure apply points and for component/location description.
Possible causes of 2nd gear stuck On are listed in the flowchart.
Verify VSS and TRANSMISSION ISS read correctly on Scan tool.
Make sure shift solenoid 2 is not intermittently sticking. Sticking shift solenoid 2 will cause an incorrect ratio in 1st gear as 2nd gear may be trying to apply. Audible sound should be similar for all solenoids. A muffled tone indicates the need for replacement.
If P0781 is active and there is no reverse, check end cover input hub seals.
2nd clutch should apply and release when air check procedure is performed. If clutch plates are moving normally and no other leaks detected, the problem is probably in the valve body. If clutches are not moving correctly, the problem is in the end cover or an internal clutch assembly problem.