code p0403

4freddie · September 8, 2004

I had the ses light come on. went to autozone to get the code read. It was p0403. Man at autozone said it was the o2 sensor load bank 2 #1. Went ahead and changed out all four since I was over 100,000 miles. Reset computer and seemed fine for about 2,000 miles. SES back on, back to autozone I go. Same code! Searched OBDII codes come to find out nothing todo with o2 sensors. It's EGR circuit malfunction. Before I waste more money is there anyway to test this? Any help would be appreciated.

budhayes3 · September 8, 2004

Best way I know is with a scan tool...Tech II would be best. Then ya gotta go into active test and check the circuit operation. Fire up the solenoid, make sure it works..

You could start with a visual inspection under the hood. Look by the egr valve/solenoid and check for broken, corroded, chewed wires or loose connectors...might get lucky and find something. If not, ya might want to look into getting a scematic to get fimiliar with the circuit.

4freddie · September 9, 2004

Okay what is a scan tool and how much do they cost

budhayes3 · September 9, 2004

A scan tool is a piece of diagnostic equipment that plugs into the diagnostic port under your dash and can be used to perform many tasks...from accessing and clearing trouble codes, to reading live data, to turning solenoids on and off, to reflashing the PCM logic and parameters, and so on.

Unfortunately, the real good ones are very expensive...thousands of dollars. There are cheaper ones plus software that you can buy, but I'm not sure of all of their capabilities.

I'd start with a circuit description and a schematic...I was able to diagnose my ABS problem that way, (it wasn't a real toughy though), and you might be able to pinpoint it that way. What year is your truck?

4freddie · September 9, 2004

it's a 97 with the 5.7l. is this the same type of scan tool that autozone uses

JimG · September 10, 2004

This what the GM Tech 2 scan tool looks like and costs:

http://www.ntxtools.com/Merchant/merchant....t_Code=OTC-3628

That's actually about $500 less than other places I've seen it go for. You can find them on Ebay for around $2,000.

Coming back down to the normal price range - there's a scan tool called Auto Xray that's about $600-$700, see here: http://www.autoxray.com/products.aspx?sub=scanners&id=28

There's also AutoTap which uses your laptop and a USB cable to read the data, more info here: http://www.autotap.com

Circuit diagrams will definitely help - either the Helms book (The real GM factory service book) or a Haynes/Chilton manual will help you there.

budhayes3 · September 10, 2004

I've never tried Autozone, but I would imagine that it would be a fully operational scan tool if they attempt any diagnosis there. Unfortunately, my books are for a 99, and they don't even list that code or I'd scan and email you the schematic. Maybe someone else here has that info they could hook you up with.

Didn't find anything with the visual inspection...no connectors unplugged or chewed or melted?

4freddie · September 14, 2004

checked everything I could think of? Sounds like it might be just as cheap to change the EGR and if that doesn't work take it to a reputal garage. Either way I'll post the results.

budhayes3 · September 14, 2004

The description of the code makes it sound like the electrical control circuit is the problem. You can test your valve if you have some decent access to it. Is it bolted on one of the sides of the intake? If you can get to it, what you want to do is start the vehicle and hook a vacuum pump to the port on the valve (if it has one). When you pump it up, the diaphragm should open creating a huge vacuum leak and causing the engine to shake and/or stall. If so, the EGR and it's passages should be OK...problems in the control circuit...whether it's a VSV or some other form of solenoid.

If there isn't a vacuum port on the egr valve, you need to manually move the diaphragm either with your hands or carefully pry with a screwdriver and check for the same results.

Now if you perform this test and there's no change...engine doesn't shake stall or studder, then either the EGR valve is stuck, diaphragm might have a small tear, or the EGR passages are plugged with carbon.

If the valve is an electronic solenoid itself, then you would have to apply power and ground to the proper terminals and perform the same test....need a schematic and manual to know how much voltage is necessary.

If it checks out OK, time to attack the electrical circuit involved.

Hope it just needs a valve

4freddie · October 4, 2004

Well I just wanted to wait awhile to make sure everything was OK before giving up the results. After reading the information you told me about I asked a guy from work a few questions. He told me to have the erased and unplug the EGR. Then drive around for awhile to see if the engine would run rough. It never did but it did set off the ses light. Had it checked and this time read P1406 which after more research discoved the computer could not recognize the poition of the EGR which makes since (it was unplugged). The guy from work said it could be one of two things. The EGR was indeed bad or like in the article you talked about just needed to be cleaned. So I took it off and sure enough there was alot of carbin build up. Scraped off the big chunks and sprayed it down real good with some carbeurator cleaner reinstalled and just fine ever since. Also after reinstalling I disconnected the battery in hopes of clearing the code. Not sure if it was a needed step or the computer just realized the EGR was working and reset itself. A big thanks to everybody for their help.

Chris97K1500 · October 5, 2004

I had a similar code (p1406) EGR pintle position error or something like that on my 97 about a couple weeks ago. I cleaned mine as well. It worked for a few days, but code came back. I have the ScanTool that is mentioned above and used it to clear the codes. Hopefully just cleaning it works for you, as they cost from $100-140. Put a new on and no codes since. Chris