I've been running KOEO tests on this 1997 F-350 truck while waiting for the intermittent no-start to rear its ugly head once again. I'm getting nowhere on that problem until it does. Meanwhile, I'm getting 334 and 654 as current codes. Even though this truck is 1997 the self diagnostic system is EEC IV. I had a decent coverage on EEC IV testing HERE.
The code description for 334 is "EGR (EVP) closed valve voltage higher than expected".
What to know here is that there is a EGR VALVE POSITION sensor mounted to the top of the EGR valve by 3 small bolts. The sensor voltage to the engine computer is how the computer determines EGR valve position. As the EGR valve moves, it moves a small steel shaft that is part of the position sensor. The movement of that shaft varies the voltage from the sensor.
The 334 is setting with KEY ON, ENGINE OFF. The engine runs fine at idle. If the EGR valve was not closing the idle should be rough. The sensor and valve appear to be new. My experience tells me that I likely have the wrong voltage from the sensor. A good place to check voltages is at the sensor connector. I should have KOEO a 5 volt reference, a sensor ground and a sensor signal voltage out to the computer. There are two colors of Ford EVP sensors, the white one is supposed to signal 0.5 volts at closed valve position. When I check the signal I have 0.96 volts. The computer is expecting to see 0.5, gets 0.96 and sets a 334 for higher voltage than expected.
With the correct voltages on the wires to the sensor I loosened the sensor mounting bolts, allowing the sensor shaft to extend slightly and the sensor voltage went to 0.5. A re-test with the correct voltage and the 334 was gone.
The fix here was to slightly grind the end of the sensor shaft. I removed just a bit at a time because you can always make it shorter, but longer isn't gonna happen. Just removed enough metal to let the shaft at rest be in the position to output 0.5 volts.
Next up.... that 654 code.
Thanks!
Kenny@ggauto.repair
