alright, my buddy's 88 gt has been throwin a CE light code 31 for a long time now. i just checked it and thats the only code. he has replaced a bunch of the egr stuff already so im tryin to figure out what i can check to make it go away. any ideas of what to check first?
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.
Listen to MR Jrichker He is in the know. I bugged him for several months and Finally followed his directions to the letter and now that code is gone. I never got a chance to thank him. Thanks the next rounds on me......