Help With Error Codes

Wuts Up Guyz!! I just bought a 1998 GTP two days ago with 140,00k miles on it and it runs great. The only thing is the service engine soon light is on so I brought it down to autozone to run the codes. I got three which are P0741,P0742,P0403 basically the guy told to look for a bad connection which I did with no luck. He kinda confused me instead of helping me so I'm wondering if its a bad solenoid or what.Thanks!!!!

Congratulations. Was the purchase through a GM dealer, used car dealer or private party?

P0403 is an EGR flow circuit malfunction. The other two are torque converter clutch (TCC) issues. There is a 25 way electrical connector to the autotransaxle located driver's side top, front of the transaxle. Did you remove the connector and re-seat it?

And welcome to AF.

Thanks I got it from a used car dealership...I haven't tried that yet which I'm gonna do first thing in the morining, how do I go about about fixing the EGR flow circuit..I'm a noob!!!! Also I have been getting about 16 mpg is this normal??

Basically the P0403 DTC indicates there is a problem with the electrical integrity of the linear EGR circuit. The output state is invalid. Either a EGR, PCM module problem or wiring in between. You can check the circuit with a multimeter (DMM) before spending the big bucks on parts. Some people try cleaning the mechanical part of the EGR valve but this is an electrical issue. Easy thing to do is check the electrical connector to the EGR and make sure there is no corrosion and there is good contact.

Also I have been getting about 16 mpg is this normal??

I have the same car. I took a reading recently and got 17.6 in the city. That's driving around 35-40 MPH, coasting to a lot of red lights, accelerating slowly, correct tire pressure, premium, etc. If I drive heavy-footed, it goes down from there, obviously. You may still be in the super-charged honey-moon mode. I'd try driving it like a granny and see what you get.

before i started having engine problems... i was getting around 21mpg with a moderately heavy foot off the start. mostly crusiin around 40 and just a little highway. maybe once a week. on premium with a lotta extra weight and electrical draw on my alternator. i was gettin pretty could economy.

Thanks everyone for the help....I looked around and couldn’t find any loose or dirty wires so I'm going to replace the EGR valve n hopefully the light will turn off.

I installed a new EGR valve but the SES light turned back on. I checked the wires & they seemed fine.Now I’m getting code P0405.
http://i34.tinypic.com/2a9ya36.jpg

Do you have access to a multimeter (DMM)? Check the PCM 5 volt reference signal at the input of the electrical connector to the EGR valve.

I have a multimeter but don't know exactly what to check???

I have a multimeter but don't know exactly what to check???

With ignition to OFF remove the EGR connector. There should be a total of 5 pins. The two far pins to either the left or right depending on how you are looking at the connector have 12 volts and the 5 volts. Check with ignition to ON only. Setup meter to read DC volts. Use red lead to prod connector. Connect black lead to any chassis ground.

From the left going right on the connector I was getting 11.8,5,0,0.1,0.1.When I was holding the connector the wires that were connected to it were grey on the left two & middle then brown,red. Could this be the DPFE sensor?

By DPFE do you mean Differential Pressure Feedback Exhaust sensor? Not installed. The input voltages are good so there is an issue from the output of the EGR to the PCM module. Could be wiring. Check and reseat the 80 pin connectors at the PCM module.

Did you clean out or check for carbon at the EGR pipe going to the lower intake manifold. Also, check the PCV valve. And make sure the o-ring is installed. You did use a new EGR gasket?

I checked all the wires couldn’t find a short, I cleaned out the intake manifold and the throttle body, the o-ring is installed and I installed a new gasket with the EGR.I still have the SES light on which is really bothering me!!

Was this a new GM/Delco EGR or aftermarket?

You've got me scratching my head now. About all I can suggest even though technically a EGR relearn is not required try the following which is supposed to force the PCM to relearn the pintle closed position.

With engine off, disconnect the electrical connector to EGR valve, take ignition key to on, reset DTC error codes/SES light with scanner and immediately take the key to off position. Then re-connect electrical connector for EGR and take the key back to on not start for at least 5 seconds. Then see what you get.

it's a gm egr.....even though i'm not geting a signal from the right side of the connector thats normal??

Where would the EGR vacuum solenoid be located? Also whats the best way to clean the intake manifold??

Everything is part of the EGR valve which is electrical. There is no vacuum solenoid.

Are you referring to cleaning out the supercharger since it is the upper intake manifold or lower intake manifold?

When I got the codes pulled a egr vacumm solenoid failure came up, but I just replaced the EGR.

As BNaylor stated, the EGR on your car is all electronic.

Can you post the actual PXXXX code that came up? Maybe you were given a wrong definition.

In my generic code list, I show this:

P1402 EGR Vacuum Regulator Solenoid Valve Short To Positive (Volkswagen)
which obviously being Volkswagen doesn't apply to your vehicle

But this would apply to your car:

P0402 Exhaust Gas Recirculation Flow Excessive Detected,

This code would be tripped if a vacuum hose was disconnected with the engine running due to the parameters the PCM uses to determine EGR flow.

sorry to bring up an old thread but where would the egr position value be located?

It is the electrical part of the EGR valve assembly and not a separate component. What issue are you having? Any diagnostic trouble code?

man the same problem since I bought the car with egr code p104...I replaced the egr,checked the wires for any shorts, and cleaned all the plugs. I'm completely stumped on the issue. Also I'm only getting about 16 mpg which I believe should be better.