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"If EVP Voltage is Correct, Why am I Getting a Code 31?"Posted 10/7/1997By Dan Jurkovski
It seems lately that a lot of On-Demand codes have been coming up and the voltage on the EVP sensor (EGR valve position sensor that is mounted to the EGR valve) is reading correctly on Fords. The problem seems to be that sometimes the wrong sensors are being installed and are therefore sending the improper voltage signals to the powertrain control module. Ford uses two different EVP sensors: a black and a white (or gray). And both will send a different voltage in the same position. At rest, the black sensor will read .75 to .95 volts and the white (or gray) will read .35 to .45 volts. If the voltage reading is correct for the sensor you have and you're wondering if this is the correct sensor for the system, there is an easy way to find out. Remove the EVP sensor and push the pintle in slowly with the sensor connected and the key on, engine off (KOEO), while watching the voltage on the brown wire with a green tracer (wire colors may vary). You should be able to hold the pintle so the input voltage is .40 volts. Then, redo KOEO self-test. If you still get a code 31, then set the voltage to .80. If you have a pass 11 in KOEO self-test, the system needs a black EVP sensor. The same is true for the opposite ... if .80 gets a code 31 and .40 passes, the system needs a white (or gray) EVP. This will only work with On-Demand (hard fault) codes. If you have EVP/EGR codes only in keep-alive memory, more than likely you have a different problem.
Every Dog Has Its Day: Anticipating Adaptive Strategy Side Effects.Posted 10/7/1997By David Sill
Beginning with some 1985 engine packages, Ford Motor Company incorporated something called adaptive strategy into the EEC-IV system. By 1987, it was in use on virtually all engine packages. In simple terms, adaptive strategy means that through software, the vehicle's computer has the ability to adapt to changes in the system, such as sensors that stray from their original values, dirty throttle plates or injectors, etc. Usually these changes have occurred gradually over a long period of time, and the computer has adapted to them just as gradually. Due to these adaptive strategies, however, unforeseen side effects can occur if a worn or dirty component is replaced or cleaned. For instance, cleaning throttle plates can result in a high idle condition and cleaning or replacing a lean injector can result in a rich condition. This is because the computer is still adapted to the old or dirty part. It would eventually re-adapt, but the process can be accelerated by resetting the computer's adaptive strategies. To reset, warm the vehicle to normal operating temperature and then disconnect the battery. Leave it disconnected for five to 10 minutes on port fuel injected vehicles, and 15 minutes on CFI (throttle body injected) vehicles. This will reset the computer to its "out-of-the-box" strategies. After reconnecting the battery, you will need to perform an idle relearn procedure. This procedure varies by engine package, so consult your service information or call for assistance.
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Copyright (c) 1996-2008. Automotive Service Association. All rights reserved.
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