P0734

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 4 is used to apply or release 4th gear clutch. The PCM controls 4th gear by controlling the ground for shift solenoid 4. The PCM will turn the solenoid Off (open the driver circuit) when 4th gear is commanded On to apply 4th clutch. Shift solenoid 4 is supplied ignition voltage from the fuel pump relay whenever the PCM commands the fuel pump relay On. DTC P0734 sets when 4th clutch still slips after the PCM has commanded high main line pressure.

DTC PARAMETERS
DTC P0734 will set if the PCM detects an incorrect actual 4th gear ratio when 4th gear is commanded On when:
- Condition exists twice in one ignition cycle
- High main line pressure has been commanded
- Transaxle is in a forward gear
- Transmission ISS is greater than 224 RPM
- Vehicle speed is greater than 5 km/h (3 mph)
- Speed noise parameter = NO
- Steady state ratio fail counter equals 255 for an in-gear failure, or the shift fail counter is greater than 100 on a downshift or upshift to 4th gear (128=0 or normal operation)

DTC P0734 diagnostic runs continuously once the above conditions have been met.

DTC P0734 is a type A DTC.

DIAGNOSTIC AIDS

IMPORTANT:
- If DTC P0745, P0746, P0756, P0758, P0761, P0763, P0766, P0768 or P0789 is set, diagnose that DTC first. A diagnosed PC solenoid, shift solenoid 2, 3 or 4 low/high circuit fault DTC may have caused DTC P0734 to set.
- Refer to "Test Section Diagnosis" for pressure apply points and for component/location description.

Possible causes of no 4th gear are listed in the flowchart.

Verify VSS and TRANSMISSION ISS read correctly on Scan tool.

Make sure the pressure control, shift 2, shift 3 and shift 4 solenoids are not intermittently sticking. Audible sound should be similar for all solenoids. A muffled tone indicates the need for replacement.