The Code That Won't Go Away

[sawwas72]

Hello All,

I hope that I am posting this in the correct forum. If not I apologize.
I'm in the States and I have a 2001 Leganza. It's been a great car and have driven it regularly. I'm giving it to my daughter to drive and when I went to get the emissions tested, the check engine light came on showing a "PO405" EGR Valve error code. That was a month ago. Since then, I have replaced the original EGR valve with 2 different used ones with no luck and recently installed a brand new Daewoo OEM EGR valve, new gaskets, and cleaned the ports and I still have the cel on with the same code. The code has been cleared numerous times and it keeps showing up after not even a mile on the road. The car runs great, I just need it to pass emissions. Yesterday I took it to a mechanic and he seems to think it's either a bad ground wire somewhere or that the ECU needs to be flashed. That would cost me: $95 for the diagnostics test, $125 to flash it, and $195 if it needs a new ECU. I've already spent $300 on this thing and if possible, I'd like to repair this myself. I guess the biggest questions I have are:
1.) What's the best way for me to try to find a bad ground? Where do I look? Are there any signs to look for?
2.) I've seen kits to re-flash the map file on the ECU,
http://www.amazon.com/GTE-Scanner-KWP20 ... B006GT6IU0
will this work? Or canI just buy a new ecu and plug it in? Will it be preprogrammed??
This is driving me crazy!
Truly, any help or advice is greatly appreciated.

[Daniel]

Will try to answer 1.)

P0405 is "EGR pintle position low voltage" meaning B7 signal from #3 of EGR is too low. Since your EGR is already changed I would look for poor contact at wiring from ECU to EGR connector.

You'll normally find the ECU behind the right leg co-driver kick panel and I believe it's the 3connectors one Red-White-Blue.
There is a possibility of poor contacts at ECU connectors, S206 (not a clue where it is, maybe behind the gloove box) and EGR connector itself.

First wiggle those connectors and see if fault light comes off.
Next use a digital voltmeter to compare voltage between D9/B1 vs #2/#4. Both should read 5volts.
Last you may try to by-pass S206 by a temporary direct link between B1 & #4 in a first time. Then between D9 & #2.

Advices are based on documentation only.
Take extremely care not making short circuit.
I take no responsability if something goes wrong. It's up to you.

P0405.JPG

Red White Blue.JPG

[sawwas72]

Thank you Daniel, I'll give this a shot tonight and let you know.

[MMamdouh]

i second Daniel's diagnosis... it is a wiring/rounding issue rather than a fault in the valve itself

MMamdouh

[sawwas72]

Thanks MMamdouh,

I'm actually working on it right now. I'm testing the harness connecting to the egr valve. Should I have continuity on all harness connections to ground?
voltage wise I have as follows:

E5 to ground-12v
E6 to ground-12v
B1 to ground-5v
B7 to ground-fluctuating voltage
D9 to ground-fluctuating voltage

testing as you suggested:
B1 to D9-5v

As far as testing voltage between #2 #4 I don't know how to go about that as those points are to the egr valve it'self as has no power without the harness plugged in.
Do I need to run a temporary jumper from B1 to #4 to supply power to the egr valve and then check voltage between #4 and #2 ?

Thank you in advance.

[Daniel]

As far as testing voltage between #2 #4 I don't know how to go about that as those points are to the egr valve it'self as has no power without the harness plugged in.

You prick a needle through each wire just before the EGR connector to make a contact. When measurement are done put a dab of glue on tiny holes that you've make to avoid further corrosion.

D9 to ground-fluctuating voltage

Not normal.

B7 to ground-fluctuating voltage

Normal if EGR is moving (engine running).
Not normal if EGR is steady (engine off).
May be linked to previous D9 variation.

E5 to ground-12v
E6 to ground-12v
B1 to ground-5v

OK.