My service engine soon light came on the other day while driving home on my 97 4.2 XL. Well I went down to the local Autozone and he read the code for me and said that it showed 401. When he punched this number into their system it came up as an EGR problem, but did not really tell me which direction to go. I would think start by taking the EGR off and cleaning it, but I'm unsure.

Can anyone help me out with this?


Thanks,

CJ

 

Before I did that I'd inspect all my plumbing for leaks. Including the intake side.

 

My method of diagnosis (while criticized heavily here on this board by those who swear by code scanners) usually begins by opening the hood and searching for the obvious before even pulling the code for the very reason you mentioned in your posting. . .the CODE TELLS YOU NOTHING, except of course a VERY GENERAL area in which the problem MAY exist. Like I said before, the codes don't tell you what's wrong, they just eliminate you having to check everything and point you in a vague direction.

Kinda like asking where a gas station is and having the guy say, "East of here". He didn't tell you where it was, but you know it isn't North, West, or South. Don't know how far East, Don't know if it's behind a shopping center, or up 1/2 block from the Barber Shop on the left side of the street. Just "EAST".

I agree with TallTomG- look for vacuum leaks, check your vacuum hoses very carefully. Look for wiring damage or connector damage on the EGR Valve itself and the harness that plugs into it.

Sometimes cheesy shops will pierce the wires with their probe leads instead of taking the time to backprobe the sensors and corrosion gets into the wires and screws up the signal to the computer - tripping a code. When in reality, the problem is a corroded wire and not an EGR valve.

If your vacuum lines and wiring are all OK, then test to see if your EGR Valve will hold a 6-10 in/Hg vacuum pull for 20-30 seconds without bleeding down. If so, then clean it good and see if that helps. If cleaning it doesn't help, or if it won't hold a vacuum. . .time to replace it, bro. This is one of those repairs that, when fixed or replaced, you must disconnect your battery for at least 15 minutes, the drive about 10 miles (continuous) to reset your computer's adaptive factors. All this time it's been correcting for the problem as it's been getting worse and worse, and you want it to recognize that it doesn't have to do that anymore- you replaced or fixed the sensor.

Hope this info helps,


---J