DTC P028: Transaxle Pressure Switch/Circuit Problem: Action
- PCM turns on "SERVICE ENGINE SOON" MIL.
- The PCM will substitute the previous transaxle pressure switch value if it is consistent with the transaxle range switch. If transaxle pressure switch value is not consistent with the transaxle range switch, the PCM will substitute D4 for the transaxle pressure switch value if the transaxle range switch indicates "DRIVE/REVERSE" and P/N if the transaxle range switch indicates "PARK/NEUTRAL".
- Code P028 will be for the entire ignition cycle.
NOTE:
Numbers in list refer to circled numbers in diagnostic flow chart, see Fig 1 and Fig 2
. For circuit identification see Fig 3.
- Checking PCM data PD71 for a failure that is present in all transaxle ranges ("1" is an open in the circuit while "0" is a short to ground.).
- Determining in which circuit the failure is present.
- Checking if the PCM is receiving the correct voltage changing between 0 and 12 volts and not recognizing it.
- If the voltage remains at 0 volt, there is a short to ground in the circuit while voltage remaining at 12 volts indicates an open in the circuit.
- Checking if the short to ground is inside the transaxle or not.
- If PD71 matches the chart, the fault is intermittent. If PD71 does not match the chart, the transaxle range switch must be giving wrong readings.
- Checking if the failure occurred while the vehicle was in reverse or not. If the gear ratio was between 2.02 and 2.23, the vehicle was in reverse when the failure occurred.
- Checking P028 snapshot data PD71 to determine exactly what the transaxle pressure switch value was at code set to determine which circuits are open or shorted to ground.