91 deville service engine soon

[cole bechtold]

i have a 91 cadillac deville and the service engine soon light recently came on and it started running a little rough and my fuel economy is going down. i think it is the O2 sensor but i am not sure. i checked the codes and it said e48. what does that code mean?

[HUF]

EGR system fault. Two EGR tubes inside the throttle body under the blades are probably clogged with carbon. Clean them up with a piece of coat hanger and you will most likely be fine. Do not care of chunks of carbon falling down. While there use some oxygen sensor safe carb cleaner to clean the bores and the BACK sides of the blades. After cleaning disconnect the negative cable for a minute to reset the computer to default values (clean throttle body bores and blades).

[Ranger]

This will tell you the DTC definitions as well as how to clear them.
http://myweb.accessus.net/~090/dtcobd1.html

[Tailfin]

I've seen a number of these cars with both tubes completely clogged and do not throw that code. There is the EGR valve, located near the fuel rail toward the driver side, and the EGR vacuum solenoid, which is nearby and has vacuum hoses going to the throttle body. Do clean the tubes, practically every one of these engines needs that, but those are your alternatives if it sticks around.

[Sevillian273]

Originally Posted by Tailfin

I've seen a number of these cars with both tubes completely clogged and do not throw that code.

I second that.

I ran a block-off plate in place of the EGR valve for a few thousand miles with no codes or any other issues. Its the same no-flow condition that blocked tubes would cause.

[ehall]

I used to get intermittent SES light on my '85 and it was traced to jumpy O2 readings, which was ultimately traced to a crack in the throttle body.