EEC-IV Error Codes
July 9th, 2008 -
CODE: 31 (KOEO) - EVP circuit below minimum voltage.
The car is throwing #31 error code. Got this weekends "playtime" in the garage scheduled I guess. My research on the Internet indicates that it probably has to do with the "salt and pepper" connectors for the engine harness.
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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.
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A good ECC-IV resource:
www.fordfuelinjection.com/?p=13
forums.stangnet.com/showpost.php?p=5899663&postcount=10
That sucks dude. Seems like its been a bad week for the 5.0s. My fuel pump went out last night.
I removed the "salt and pepper" extension and cleaned up the contacts. My issue appears to be fixed, I will check the codes again when I get home from work tonight.
I don't have all the hard data yet, but my fix seems to have improved my gas mileage. At nearly $5 a gallon, this was a good fix.
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