[Nelly]

I have a 2002 PT Cruiser (inherited from Mom) with 124k.

Recently I was on the highway with it and suddenly I smelled a mild electrical smell. A few seconds later the check engine light came on.

I continued until I had a safe place to exit and check it out. Long story short, it coded for PO403 (egr circuit open/shorted).



I bought a new egr valve for it and am waiting to have it put in. However, I decided to try the electrical transducer part to see if it would clear the code. So i disconnected power from the computer (fuel pump fuse), installed it just as the old one was and reconnected power. No check engine light. Put it in drive, 30 seconds later, check engine came on again for po403.

Should I assume that there is an electrical issue? I tried looking the wiring to it all over and none seemed burned. Is there a fuse I can check? Did something blow? Hopefully not inside the computer.

Is there a wire I can get the voltage from (say by splicing) that can recover this problem?

Can I fix a potential wiring problem or is this a job for the dealer.


Thanks in advance....

 

[ImperialCrown]

See if you can find out what was burning. Check the old EGR transducer for melted plastic.
Many times a plugged catalytic converter will force hot exhaust gases into the base of the transducer and melt the plastic.
I would replace the EGR valve as well if the PCM is not passing an EGR test. The new valve and new transducer work together.

 

[Nelly]

Well, I had the egr and the transducer solenoid replaced but it didn't solve the problem. :angry2:

The mechanic says that the voltage needs to be about 10 volts and the egr connector is only getting 6 or 7.

He says that there is either a broken wire, or something is wrong with the computer.

Anyone ever experience this before?




Also, one thing I did notice is that once the engine light did go off while I was driving, only to come back on a short time later. That only happened once.


I'm starting by suspecting a green with orange stripe wire that is bolted to the side of the valve cover (the right side). It is hooked up to small prong. It looks like it would be a ground wire, but I'm not certain. Does anyone know what that wire does?


Anyone have any ideas? Am I doing any harm driving it like this? It seems to drive like it usually did.

Thanks in advance....

 

[ImperialCrown]

The component at the rear of the valve cover is probably just a radio noise suppression capacitor.
The (+) side of the solenoid is 12 volts. The (-) side is a duty-cycle (pulsating 0-12 volt) that may not measure well with a digital voltmeter and the 6 or 7 volts may be the duty-cycle 'average' voltage.
If the 12 volt side is low, you have a load pulling down the 12 volts or a high resistance in the 12 volt supply. That Gn/Or wire supplies other 12 volt components like the fuel injector and ign coil feeds. Are their Gn/Or wires at 12 volts?

 

[Nelly]

I don't have a multimeter to find out what the voltages are. If I get one, I'll probe around to try to see what's happening.

I'd really like to vote out the computer being bad, just to give me that sense of confidence, but I'm really unsure.

Something smelled electrical a few seconds before this happened, and it wasen't a part of the egr. I can't find what it was.

Does anyone know where all the grounds are? Maybe I can start there.....

 

[ImperialCrown]

You will want to start with a cheap pocket-sized digital volt-ohmmeter. These are useful for home and car.
You will also need to trace that Gn/Or wiring circuit if that's where you think that the low voltage/burning problem is. Grounds are a return circuit after the load and usually don't burn up, but can have poor connections. I would more suspect a 12 volt/current carrying wire getting hot.
The wiring diagram, connector pinouts and ground locations can be found in a good service manual. I find that the factory service manuals are the most detailed and accurate with circuit, ground and connector locations. Wires can change color following their path.
Main public libraries may offer free information like this. The city library here has a large amount of service manuals including a subscription to Alldata: some factory (Chrysler), Mitchell, Motor, Chiltons, and Haynes. The latter 2 are less helpful than the first 4. You can usually take these home with you or photocopy what you need.
The internet also offers free or subscription wiring diagram service information that I can't vouch for. Google will bring up results for almost any inquiry.

 

[Nelly]

I'll start the search soon to get the items you suggested and try to see what the wiring is up to.

In the meantime I have noticed that sometimes (very sporadically) the check engine light will go out!

I'll celebrate that it's off, only for it to return moments later.

Is that a good or bad sign. That a wire is intermittent and it corrects itself, or that the computer is randomly resetting itself?

Can a computer really be bad over this one egr wire malfunction?

 

[ImperialCrown]

The PCM tests the EGR circuit for shorts or opens constantly. It may be intermittent and not a hard failure. When diagnosing this, you want it in failure or everything will test fine.
I doubt that the PCM has been damaged, it has protections from over-voltage, reverse polarity and shorts (over-current).
An open offers no load and won't damage the PCM or circuit.
A poor connection on a current-carrying wire will be a high-resistance and will create heat. Depending om the amount of current, things can get hot enough to burn.
Maybe sniff around under the hood for the burnt smell to locate the problem area and look for burnt plastic/wiring?

 

[Nelly]

Thanks Imperial......

I think thought I found the problem.

I was looking over the wires to the EGR closely again last night and I came upon one of the two wires (forget which one right now, I think it was the white one) that felt like a thin piece of pasta. It was very wiggly near the connector. I barely gave it a tug and it separated in two!!

Turns out the wire broke inside the isolator, very close to the connector. I exposed some of the wire and pushed it into the connector, repairing the "open" of the P0403 (open/shorted connection). Then reset the computer.

I drove to and from work today and the check engine light has not came back on.


:yahoo:

 

[Nelly]

This just in....

The check engine light came back on tonight (after two days) for po401 (insufficient flow of egr). :thumbsdown:

I really don't understand this since I just put a brand new EGR and transducer on.

Out of plain anger, I reset the computer (figuring this has got to be a fluke) and it did not come back on the 4-5 miles I drove home.

What do you think is up? :frustrated:

Thanks again for your help.

 

[Bob Lincoln]

The orifice under the EGR valve is clogging. It's a common problem with some cars. Take the valve off, spray the orifice with carb cleaner, dig at it with a sharp piece of wire or something to break the crud loose.

 

[Gerry G]

I went through the excercise of resolving the P401 on my wife's 2002 PT Cruiser. The P401 is actually
triggered by the MAP sensor looking for a predetermined change in pressure when the egr opens.

When I got the 401 code, I changed out the erg valve itself, not the problem. I next changed out the MAP
sensor since it is used to trigger the code, again not the problem. Talked with local mechanic and he noted
that the intake plenum sometimes carbons up where the exhaust gas enters the plenum and suggested
pulling it off and cleaning it real good with carb cleaner. So off came the intake plenum. No significant
carbon build-up but it got cleaned up good. No change, the 401 code showed up again.

So now I go back and recheck everything. It was then I found the problem. As I was pushing aside 'stuff'
I noticed the the pcv hose was very soft. I pulled it out completely and saw that it had small cracks in
it. Replaced the hose and the 401 has not returned. Apparently the pcv hose was letting in just enough
air (very slight vacuum leak but not enough to notice) so that when the egr opened there was not enough
of the expected difference in the manifold presure and thus the 401 code.

So, I would first check out the pcv hose; if it soft or has cracking, replace it first. If the code reappears
I would next replace the MAP sensor. It the code still appears, you may need to pull the intake plenum
and clean it out.

Hope this helps.

Gerry G.

 

[ImperialCrown]

The P0403 code is EGR circuit open/short and appears to have been resolved with the broken wire repair.
If the plastic wire insulation was intact but the inside conductor was broken, I suspect that the wire got pulled on.
The PCM is now setting P0401 which means that it is actually now able to test the EGR performance.
Agree with now looking for plugged EGR plumbing and/or intake manifold vacuum leaks. As stated, the rubber hoses must be in good shape. Not oil-rotted, softened, swollen or cracked.
If the upper intake manifold has been removed to change the spark plugs, make sure that everything is fastened back in place. The rubber intake runner seals, etc are usually re-usable, but I have found them pinched or folded over from an R&R intake and in need of replacement.
A vacuum leak will generally raise idle speed as it is air added below the throttle blade. The PCM looks for a drop in intake manifold vacuum when it opens the EGR valve to test the EGR operation. If the expected vacuum drop is insufficient or not there, it will set P0401.

 

[Nelly]

I think to start off there is a slight crack in the PCV hose!! I've been looking around for possible problems other than the valve (since it's not that easy to remove and I had it installed recently). I'm going to check that over again and see. Sorry about the delay responding, but with work (and this darn car) there's not enough time in the day.

I'll let you all know what I come up with.

Thanks in advance.

 

[Nelly]

Okay, I went in and repaired the crack in the hose and replaced the pcv valve. I also reset the computer. As I'm waiting for the drive cycle to complete (to see if the CEL comes back on), the car had started driving very very sluggishly....


It drives bad. It sometimes doesn't keep it's idle and drops low to almost 500 rpm, threatening to stall. When you leave from a stoplight, it's VERY sluggish as if it's really starved for fuel.


I'm thinking that it maybe was a bad computer reset? Maybe I drove away too early rather than let it learn an idle?

What do you guys think is up??

By the way, what's the correct way to reset the computer and let it learn what it has to? If I reset it again, I want to make sure I do the learning the right way.

Thanks in advance!

 

[Bob Lincoln]

See my post #11.

 

[Gerry G]

I would suspect a vacuum leak; what you describe can be caused by a lean condition. Note, there is a vacuum hose back
near the firewall by the brake master cyclinder that will fall off very easily if you are in that area of the motor especially
working near the egr.

Hope this helps,

Gerry G.

 

[Nelly]

My apologies for the delay in responding but I went on vacation shortly after writing my latest message.

I went back to the mech that put the egr on and he removed the egr tube and said it was clean inside and he recleaned it just because.

It still seems to run the same. It's very sluggish when driving and sometimes dips in idle below 600. It (most of the time) just does not want to keep it's idle. It's always creeping up to around 1100 or dips and bounces as it coasts to a stop.

It's frustrating since my parents got a new(er) '06 and it drives and idles just as it should.

No check engine light (as of now).


I will check to see if there is a loose hose somewhere and report back.


By the way, does anyone know what the symptoms of a failing fuel pump are?

Thanks in advance.

 

[ImperialCrown]

Failing fuel pumps can affect fuel pressure. You can drive around with a fuel pressure gauge attached to the rail and run out the back of the hood to view at the windshield. A 4' hose should reach and you can pin the gauge under a wiper to hold it still (as long as it isn't raining).
Make sure that the hose is away from hot or moving parts and no leaks are present while running before closing the hood and starting out on a drive.
Fuel demand at idle is very low, so fuel pump problems usually don't show up until the pump has to meet an uphill run or high-speed/load demand.
At idle, a voltmeter on your TPS signal line should show a 'rock-steady' voltage. If it varies or 'tickles' up and down slightly, the PCM will view this as you playing with the gas pedal or throttle. It can be intermittent. You should see around 0.67 volts at idle and it should stay right there.
Walking signal voltage is typical of TPS wear and it may not set a fault code. The PCM would only set a fault code if the sensor signal is open or shorted or out of agreement with what the MAP signal says. If the sensor signal is still believable, the PCM won't set a code for it.
Too much EGR at idle can also cause a poor idle as it is also a 'vacuum leak' in some respects.

 

[Nelly]

hmmm, thanks for the info. I have a spare tps that I'll swap in and see if that helps.

Seems fine when going up hills , however, it just is reallllly slow to get up to speed. Its as if its starving for either air or fuel. Once it gets going, it's fine.