I just bought a 2001 subaru outback with 170,000 mile. a lot of miles i know! it hesitates a little in shifting(its an auto). the check engine light came on today. any ideas?

I found this under Fixya; 2006 Subaru Outback; there were 25 answers: The problem is not with an emission issue as you would expect with a check engine light. The ER 55 code on the odometer means that there is a loss of communication with the ECU, that is why the check engine light is on and cruise light flashing. for what ever reason whenever your check engine light comes on the cruise becomes disabled. Lame I know. I work in the service department and have seen this issue a lot. The only real way to fix this issue is to go the dealer and have them do a reflash for your vehicle. If the ECU is bad it is covered under the federal emmission wrty for 8 years or 80,000 miles

If you are saying it takes a long time to start the engine, have you checked fuel pressure before and after cranking ?

Sounds like the belt let go and maybe got jammed on the way out. The belt power the alternator, power steering pump and water pump etc. Check for a seized pulley as well. Sometimes the little bearings go.

Every vehicle mfg. has a recommended about of miles to do this. It should be in your owners manual.
Every tech has a different answer for this as well, but the mileage it has now is about the time to do it.
I would have a reliable auto center, flush, change filter and re-fill.
They have the special equipment to do it right.
Get a few estimates first.
You can expect to spend about $ 125- $175.00.
Please let me know how it goes.

I do not know for sure if this is the problem you are having, But, I have noticed that from 95 up to 2002 I have seen a lot of PO420 codes that have been just the sensor. I do not know if it was a weak sensor or just that program telling it that it is below threshold. I did notice that if the vehicles are run for a long trip at highway speed it goes out. I wish you luck and have a great day.

This could be a lot of different reasons. Take to Auto Zone for a free diagnosis check.

timing belt needs to be replaced at 100,000 miles, auto transmission fluid and filter replaced, that is really the only things, of course u check all fluid levels, the big maint is the 100,000 mile service

There are several things that will turn the check engine light and TCS light on .If you get the code I can tell you exactly what the problem is . On your year i see transmission problems as well as EGR problems. If you go to any large auto parts store they will check the code for free or a very small fee.

looks like you need a good tune up its a little early for this engine but i have seen alot of bad plug wires this year. so at least plugs and wires.
i think this should cure your problem
later paul

I just bought a 1999 Outback with the same problem, the previous owner says replace the PCV valve

Hope it works