Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Code P028, Transaxle Pressure Switch/Circuit Problem: Action
PCM turns on MIL. PCM will substitute previous transaxle switch value if it is consistent with transaxle range switch. If not, PCM will substitute D4 for transaxle switch value if transaxle range switch indicates Drive/Reverse and Park/Neutral if transaxle range switch indicates Park/Neutral.
- Checks PCM data PD71 for failure that is present in all transaxle ranges ("1" is for open circuit and "0" for short to ground).
- Determines in which circuit the failure is present.
- Checks if PCM is receiving correct voltage changing between zero and 12 volts and not recognizing it.
- If voltage remains at zero volts, circuit is shorted to ground. If voltage remains at 12 volts, circuit is open.
- Checks if short to ground is internal or external of transaxle.
- If PCM data PD71 parameter values are as specified in Code P028 (1 of 2) diagnostic flow chart, problem is intermittent. If parameter values are not as specified, transaxle range switch is giving wrong readings.
- Checks if failure occurred while vehicle was in Reverse or not. If gear ratio was 2.02-2.23, vehicle was in Reverse when failure occurred.
- Checks Code P028 snapshot data PD71 to determine exactly what transaxle pressure switch value was at when code was set to determine which circuits are open or shorted to ground.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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