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FFCobra Craftsman
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1,067 Posts
Discussion Starter #1
Now that I have a working "check engine" light in the roadster I did a KOEO test. I got three codes, two of which I know (and caused), the last one though I need help with. It is code 31 - EVP circuit below minimum voltage. What is this and how do I fix it? Thanks.

Greg
 

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Senior Charter Member
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393 Posts
Tech Tips

"If EVP voltage is correct, why am I getting a code 31?"
by 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.

Dan Jurkovski is ASE master and L1 certified. He is an AutoLine Ford specialist with 20 years of experience.


Every dog has its day
Anticipating adaptive strategy side effects.
by 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.

Dave Sill is ASE master and L1 certified. He is an AutoLine Ford specialist with 12 years of experience.

AutoInc. Magazine ®, Vol. XLV No. 10, October 1997
 

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FFCobra Craftsman
Joined
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1,067 Posts
Discussion Starter #3
Solved my engine code problem (sort of, still have purge canister code). Check all electrical and vacumm connections, cleared computer memory and started engine. Check engine light came on in about two seconds. I let it run for about 15 minutes then started trying stuff. Pulled the vacumm line off the EGR valve, attached a length of hose, and gave it a suck (no jokes please :D ). With a pop the valve opened, it was stuck. Check engine light went off. Hooked the vacumm line up then shut the engine off. Ran the codes, just an 85 (purge canister), and nothing else. Life is good again.

Greg
 
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