Help With Error Codes

[RedGuy]

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!!!!

[RedGuy]

[BNaylor]

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.

[RedGuy]

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??

[BNaylor]

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.

[rkvons]

Originally Posted by RedGuy

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.

[TDWPgtp]

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.

[RedGuy]

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.

[RedGuy]

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.

[BNaylor]

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.

[RedGuy]

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

[BNaylor]

Originally Posted by RedGuy

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.

[RedGuy]

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?

[BNaylor]

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?

[RedGuy]

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!!