Codes P0401 and P1739 appear. No problem noticeable issues while driving car. Happened before and repair shop said they could try two different repairs, but they were not sure what is was. Paid the one hour labor and left. Now, six months later, it is appearing again.

 

P0401- insufficient EGR flow.

Most likely clogged EGR port.
2.3 requires upper intake plenum removed and port cleaned, ~$5 gasket and hour worth of work.
3.0 requires partial intake removal to properly clean EGR port. ~$15 gasket and hour worth of work. Make sure to get the gaskets with both upper and lower plenum gaskets just in case you need to fully remove intake.

Check FAQ at top of page on how-to-DIY.


P1739- 3rd gear pressure switch.

Check wiring for damage, sensor for leakage. If neither pull sensor off and check for debris inside the switch clogging it, clean it and reinstall if clogged.
2.3 3rd gear pressure switch is located on the front lower right side of the car/transmission.
3.0 3rd gear pressure switch is located on the front lower left side of the car/transmission.

Both will be located near the main shaft sensor which is bolted on, oil pressure switch is screwed on.