EGR Code 31...Where do I start?

onebad7up · Jan 26, 2007

I have been trying to figure out why my car has been bucking lately. It is an AOD and after it shifts into the next gear and if I have my foot on the gas a little the car will buck. I have been told it is the MAF, TPS and EGR. I bought a code reader last week and I ran the codes today. Whenever I read codes when the car is not running I get code 31 (Cannister or EGR valve control system signal out of spec or EVP voltage low). Is this common?

jrichker · Jan 26, 2007

CODE: 31 (KOEO) - EVP circuit below minimum voltage. Vref (5 volt reference voltage supplied by the computer) missing or broken wire or bad connection in circuit. Use a DVM to check for 5 volts on the orange/white wire. If it is missing, look for +5 volts at the orange/white wire on the TPS or MAP sensor located on the firewall near the center of the car. Use the black/white wire for the ground for the DVM.
With the sensor removed from the EGR and still connected, press the plunger and watch the voltage change on the brown/lt green wire. Pull the passenger side kick panel and measure the voltage at the computer. You will need to remove the plastic cover over the wires and probe them from the backside. A safety pin may prove very useful for this task. Use pin 27, EVR input (brown/lt green wire) and pin 46, signal ground (black/white wire) to measure the voltage. The orange/white wire is Vref and should always be 5 volts -/+ .25 volt. Be sure to measure Vref at the EGR sensor to rule out any broken wires or bad connections.

onebad7up · Jan 26, 2007

I have 4.98 volts at the TPS but I am not sure where the MAP sensor is. Is that the same as the baro sensor? If so, I do not see a orange/white wire. I am going to go and check the egr connector right now. If I dont see anything here I will go to the computer next.

Thanks for the help so far.

89streetbeast · Jan 26, 2007

onebad7up said:
I am not sure where the MAP sensor is. Is that the same as the baro sensor?

map sensor is the same place as where a bap sensor would be right on the firewall behind and above the intake.

onebad7up · Jan 26, 2007

I took a few pics of my firewall. I cannot see where the MAP sensor would be.

http://classifieds.stangnet.com/showfull.php?product=40315&bigimage=100_0189.jpg

http://classifieds.stangnet.com/showfull.php?product=40315&bigimage=100_0188.jpg

Also, took the connector off the EGR but I do not see how to operate the plunger. Do I need to take the entire sensor connection off (three nuts holding it on)?

89streetbeast · Jan 26, 2007

that 1st pic is the map sensor.

89streetbeast · Jan 26, 2007

onebad7up said:
Also, took the connector off the EGR but I do not see how to operate the plunger. Do I need to take the entire sensor connection off (three nuts holding it on)?

no you take the whole egr valve off. theres 2 nuts. you will see the pintle on the valve when you remove it to operate the plunger.

onebad7up · Jan 26, 2007

Oh ok. I just replaced that too. I thought it was the baro sensor. Where is the baro sensor then or are they the same thing?

89streetbeast · Jan 26, 2007

bap or baro sensor is used on pre 88 non-cali cars. it looks like the map sensor but has a vacuum line going to it.

jrichker · Jan 26, 2007

onebad7up said:
I took a few pics of my firewall. I cannot see where the MAP sensor would be.

http://classifieds.stangnet.com/showfull.php?product=40315&bigimage=100_0189.jpg

http://classifieds.stangnet.com/showfull.php?product=40315&bigimage=100_0188.jpg

Also, took the connector off the EGR but I do not see how to operate the plunger. Do I need to take the entire sensor connection off (three nuts holding it on)?

Yes. Remove the 3 nut and you will be able to remove the sensor and see the plunger.
That's what you push on.

Diagram courtesy of Tmoss & Stang&2birds

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

89streetbeast · Jan 26, 2007

jrichker said:
Yes. Remove the 3 nut and you will be able to remove the sensor and see the plunger.
That's what you push on.

yea thats right my bad, was thinking about the egr itself and cleaning the carbon off the pintle

onebad7up · Jan 26, 2007

So when I take that off tomorrow should I go ahead and clean it out too?

89streetbeast · Jan 26, 2007

if its stock egr i would, never hurts to clean it. i used some carb cleaner and a small wire brush, kinda like a toothbrush.

HISSIN50 · Jan 26, 2007

A bore brush works quite well.

89streetbeast · Jan 26, 2007

HISSIN50 said:
A bore brush works quite well.

that tool was tryin to say that but my mind was off lol

onebad7up · Jan 27, 2007

Ok. Well I am going to go check voltages at the EGR and the MAP. If I have proper voltage at these locations I shouldnt have to check the comp, right?

PJB · Jan 27, 2007

I had the same code and cleaned the needle on the EVP with carb cleaner and a toothbrush and havent had a code since. That was atleast 800 miles ago (I dont drive the car alot so the miles dont go up alot).

onebad7up · Jan 27, 2007

Well I just checked the MAP, EVP and TPS voltages. They all had the correct 5 volts on the orand/white wire. I also did the plunger test on the EVP. The MAP is new. The one thing I did notice was that the TPS voltage from the green was not set properly. I filed the holes down and set it at .985. I am hoping this was the problem. Could this fix it?

onebad7up · Jan 30, 2007

I have been driving the car and it has been a lot better. I would like to completely get rid of the bucking though.

What happens to a bad TPS?

It seems like everytie I check it I get different readings. Should I just buy a new one?

HISSIN50 · Jan 30, 2007

The computer should zero out the TPS continuously - either the TPS zeroes out or it pops a code. I would not sweat a slightly changing TPS reading unless you have reason to believe it's caused by bad wiring or it changes drastically.

Good luck.

EGR Code 31...Where do I start?

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