Error Code P0405.
2001 Pontiac Firebird Base Convertible 3.8L engine. Over 264,000 miles.
I've been having this problem for more than 4 years. No matter how many times I've changed the EGR Valve, the error always return (I have a lifetime warranty on my EGR Valve, so it's not an issue getting a new one.).
1. I've removed and cleaned the EGR mount bracket.
2. I've cleaned the air intake path (wire brush and chemicals) until I had a shine.
3. Replaced MASS airflow sensor
4. Replaced IAT sensor
5. used fuel injector cleaner numerous times.
6. for the past 3 years only use the highest grade Shell Gas.
7. I'm wondering if the real problem is a leaking hose? (my next step after getting your help is go to the GMC dealer for a engine diagnostic. Service agent already said that he will need the car for a couple days!)
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About my Firebird:
I'm new to LS1Tech. Hello everyone!
I'm restoring it back to showroom quality, except I added the WSQ hood, and I want to upgrade the exhaust and muffler. I bought a Flowmaster 80 series American Thunder, that I need to install. I'm spend over $5000 over the last 3 years. I wish I could just find a local shop to get everything done all at once, but that will be for another thread. I bought this care in January of 2004. I think it had about 23,000 miles on it. It has a LOT of highway miles on it. I've driven it from Indiana to OKC several times. Now I live in Washington, DC. I drove it there and back twice from Indiana. The Firebird has been my secondary car since 2013. Since then, I don't drive it in the snow anymore, and I hate driving in the rain (because I'm pampering the car now). I do not like to have it parked outside. I have a few very small dents to smooth out in one quarter panel, then I'm getting the whole car repainted with factory color, Midnight Metallic Blue. Then the outside is done, and work starts on the inside. I want to changes the carpet, reupholster the seats, add sound deadening, add interior lights, convert my bulbs to LEDs, and paint the gray dashboard to match the beige seats and carpet, add a wind deflector, and maybe upgrade my convertible tonneau covers.
1. Engine rebuilt 2014 @ 247,536 Miles
2. bought WSQ bolt-on hood.
3. Transmission rebuilt
4. Replaced convertible top with OEM material.
5. Replaced whole AC system (OEM parts and it's hoses)
6. replaced heating coil
7. replace fuel pump
8. Upgraded wheels to 18". Pics coming in a different thread.
9. Replaced rocker panels. (at first I grinded the rust off myself and put enamel over it. Then I just to have replacements, from Ebay, installed. I'll get the whole car repainted the factory color this spring or summer 2022.
10. I still need to install my Blind Spot Sensor Monitor System. (I'm willing to trade or sell my brand new in the box spare one. I didn't want to install it after of found out there are models that don't require holds being drilled into the bumper.)
11. I added a backup / parking camera. Yes, I upgraded the radio. And Yes, I'm keeping the old one. I looked up how to add an AUX jack to the radio. I'll do that later, then buy the rear view mirror with the built-in backup camera screen.
12. I need to find someone to install my new window seal weather strips. (I may take a shot at it myself)
13. I have Firebird mirror tiles to preplace my convertible's sail panels. (there are two)
14. I need someone to install the Firebird project lights under my door seal. (when the door opens, a color firebird logo shines on the ground.)
15. I need to install my Headlight LED conversion kit. (it arrives this weekend Feb11th. (I'll post pics in another thread)
16. Need more interior lights. the convertible version is very poorly lite in the cab.
***** 17 *** I want to buy a SPORT LIGHT BAR. They are discontinued like everything else, but some junk yard has to have one somewhere!

18. I have been keeping ALL of my maintenance receipts since 2014. I scan them into the computer and I make a print out to keep in a 3 ring binder (almost an inch thick). Most of my parts are AC Delco OEM parts.

 

You could have a wiring or PCM fault. If new valves haven't solved the problem, you will need to trace the voltages in the circuit: https://www.obd-codes.com/p0405

You may find some videos on youtube that will show you how to do this for this particular code. Having a dealier do this will be very expensive. (The hourly rate for electrical diagnostics is typically higher than mechanical work.)

 

Thanks. I'll see what I can find on youtube. I'm so fed up with this problem, I'm willing to pay the money for the dealer, if youtube can't help. I'll take a look at the link you posted too.

 

EGR System 2001 Firebid 3.8

#4 EGR Valve Connector - Can you check the connection, wires & pins? Need to see if PCM is sending signal. #3 Any cracks in pipe?

#5 EGR pipe check for cracks #8 Purge Valve - check to see if valve gets signal and works?


Brief outline of the EGR system and parts. Hopefully someone with in depth knowledge can make suggestions. I took a few guess at stuff to check etc.




FWIW - my 91 RS had EGR issues sometimes due to carbon build up. Dearborn treatment might help. Also the EGR relay failed one time, got a same code as EGR Valve but it was the defective relay.

 

EGR removed from mount, and mount paths cleaned.

Removed throttle body. WARNING! Coolant flows through the bottom, and you will loose a little coolant. Just enough to make an annoying mess!

The port hole in the back, leads to the EGR valve. It's a VERY common clogging point. Mine still looks good from 2 years ago. I cleaned it anyway. The port hole in the front goes to a sensor. I think it's a purge valve. I cleaned it also.

using a brush to clean the EGR path.

Using a brush to clean the sensor port hole.

My throttle body could use some cleaning. What is that door flap called?
1. My multimeter come in the mail tomorrow, I'll test the wiring then.
2. Today I removed the throttle body and cleaned everything with a carb cleaner. Additionally, I clean the port / tubes leading to the purge valve, and the EGR pipe. I'll be sure to clean the mount / bracket tomorrow.
3. I removed all the sensors from the throttle body and clean the carbon away from the inside door flap (sorry, I don't know the name of it).
4. My throttle body gasket is supposed to come in tomorrow, so I'll put everything back together tomorrow.
5. I tried the trouble shooting technique of starting the car without the EGR valve connected. a) if the engine runs like normal, then you know there is a clog in the EGR's air flow path. b) if the engine idles high or stalls, then there isn't a clog in the flow path. SMH, why did my car do neither!!! It just "sputtered" continuously. It barely ran, didn't stall, and idled slightly loud. smh, why me. Will I'll have a volt meter tomorrow, and I'll start trouble shooting wires to the EGR valve.

I shot some video, but forgot to take pics (since they would post better to this site, I'm guessing.)
I'll add pics and what I'll do next tomorrow.

 

Following trouble shooting instructions using a digital multimeter (DMM), I found that the C wire in the EGR connecter isn't receiving 5 Vdc. That's the wire / voltage that controls the pintle (valve) inside the EGR. I guess I'm on the hunt for an open wire somewhere.

 

I used my DMM to test the EGR connector. I'm not getting the 5Vdc reference voltage. I'm going to need to find the pin-out for the PCM to see if the 5Vdc is leaving that unit.
Here is the test from Part 1 -How To Test the GM EGR Valve -Buick, Chevy, Olds, Pontiac (easyautodiagnostics.com)
1. With the connector on the EGR (the EGR doesn't have to be screwed down to the mounting bracket).
2. The key turned to the "on" position. (engine not running)
3. Black lead to ground and the red lead to the C pin (wire #3)
a) I used a safety pin to into the back of the connection, to make contact with the metal in the connector.
b) I discovered it is easier to just push the safety pin through the wire's conductor coating, to make contact with the wire itself. (unless you have the special test tool to that cuts into the wire's outside coating)

 

Sounds like you're doing great trouble shooting. Any new updates?

 

Yes, I have updates.
The SHORT ANSWER:
Catalytic converter (Cat) was SO clogged, that it was causing failures in the front in of the exhaust system, and causing the PCM to give false readings. The PCM trying to compensate, has been ruining the cheap Autozone EGR valves. I've never changed the Cat since I bought the car in 2004. This all makes since, now. 1 bottle of CataClean got the engine light to turn off, and improved the driving acceleration, just a little. I'll be definitely replacing the Cat!

The LONG ANSWER:
I pulled back the EGR cable wrapping to see if there were any obvious breaks or pinches to the wire carrying the 5 Vdc, but not trouble found (NTF). I almost spliced 5Vdc from another sensor, before coming to my senses. At first everything was pointing to the cable wiring from the PCM or the PCM itself. Those are some expensive replacements, it would take time for an order to come in, and I don't know how to program a new PCM. What else can I do? I can fix other failures.
1. The real issue had ruined the EGR, because the PINTEL (the valve part) was sliding around by itself. Like a baby's rattle. I know new ones don't do that.
a) I got the life time warranty from Autozone. Swapped it out.
b) I manually cleared the fault code with my tester.
c) Used the voltmeter to trouble shoot again, to be sure I did everything right . . . and for practice. SMH, why did everything test good, even got the 5Vdc.
d) EGR removed from the engine, but wiring connector still connected; I cranked the engine. The engine idle was very high, as it should be.
e) according to trouble shooting guide, there is no blockage before, or in, the EGR valve.
2. Test drive the car, and still having accelerating problems. The check engine light returned, no surprise. The code changed from P0405 to P0420.
a) P0420 points to catalytic converter. This makes since with the trouble shooting results, and according to trouble shooting guide.
b) I put a bottle of fuel injection cleaner, then drive the car down to a 1/4 tank.
c) 1 bottle of CataClean. The check engine light cleared. The engine performance & acceleration improved, just a little. I see that I need to replace the Cat, ASAP.
3. I already have the exhaust from the Cat back (with a Flowmaster's American Thunder muffler). I just have to get it installed. I will be buying the y-pipe and Cat very soon. I may just get the headers too.

Thank you guys for the help. It all lead me through the trouble shooting steps, and saved me money. I would have never believed the dealer if he told me what I found out for myself.

 

Wow. Thanks for posting the complete story back. Your experience will hopefully be instructive to others.

Tracing the wires on the senors is hard to get right, particularly without specialty probes to get into the connectors and make those connections.

I'm glad it worked out!

 

Bimron, glad you solved the problem A++.
A++ for sharing the outcome and solution!

That will help other people out.

 

Pic and trouble shooting link has been posted. Good luck to everyone else!