Pulled codes, code 31

sunil6784

Member
Mar 31, 2005
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18
Boston, MA
On my last tank of gas, I only got 14.5 mpg. So i pulled the codes just to see what I would get. I got a code 31 in the memory. I already searched and found jrickher's reply:

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.

Where it says to check for 5 volts on the orange/white wire, where is this ? When i check for voltages, do i have to strip the wires? Also, where is the EGR valve? I used to get around 17 mpg, so when i fix this, will I get better mileage or about the same?

Thanks for the help...
 
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Check the orange wire on the TPS and MAP/Baro sensor on the firewall. Use a safety pin to slide down the backside of the connector to make contact with the pin inside the connecor. Or you can disconnect the connector and probe from the front side.
Diagrams courtsey of Tmoss (diagram designer) & Stang&2Birds (website host) http://www.veryuseful.com/mustang/tech/engine/
TPS_IAB_Pic.jpg

A properly functioning EGR will increase gas mileage.

Check the 10 pin connector for the Vref voltage too.
diagram courtsey of http://fordfuelinjection.com/index.php?p=6
harness02.gif
 

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