That old check engine light again

Got 52, 000 and some odd miles on a 2001 Cherokee and have had three instances of check engine light previously. One resulted in a cleaning of the intake manifold. Other two both resulted in same fix "pump for emissions". Now its on again. Anybody got an idea what the real problem is likely to be?

Driveability and gas mileage seem unchanged.

Last time and this time occured very soon after oil change.

reader

If you have a laptop or palm you can get one of these http://www.ghg.net/dharrison/obdscan.html and see for yourself why the light is coming on. I consider this some of the best spent money I've put into my XJ.

Still got the problem, does anyone have any ideas on what the problem really is? Dealer(s) don't!

NO2

Just a guess since you don't have the codes. Oil changes usually improve nitrous oxides which are a result of unburned fuel in your motor oil from blow-by. The fumes are routed back into the intake which uses exhaust gas to help burn them. If in fact the oil change and light are connected then check your egr system. Of course without your codes there is no way to be certain that this is what is setting off your light. Go to AutoZone or any other autoparts store that checks your codes for free and get the codes and let us know.

I'd take it back and toss it in the dealer's lap. Just have copies of your tickets and show that they still have not fixed it yet. Documentation is your friend at times like this.

I did that with the cruise control on my XJ, just left with them until they got it fixed. They had it 2 months but I have a second car so no problem.

Also since you are a repeat you may be able to get a car out of them under warranty. I am sure the first time was when it still was under the factory warranty. This being an emission item you may have a 100,000 mile warranty.

The last thing you want to do it let the dealer off without fixing it. Just tell them it is still not fixed.