Help with troubleshooting the codes

i got a 93 taurus, 3.0 engine, GL... i had the computer checked and these are the trouble codes 25 Knock Sensor 34 EGR valve position sensor (EVP voltage out of range)
51 ECT (engine coolant sensor) how do you test these sensors to see which one is bad??? or is there a common thing where one is going out then you get incorrect readings from the others??? thanks for a reply....
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Note that a sensor code does not necessarily indicate a faulty sensor. It is critical not to overlook the wiring associated with the sensors as well as related systems. Regardless, the sensors can be generically tested with an oscilloscope or graphing meter as follows:
Knock: locate the sensor, and lightly rap on the block nearby with a screwdriver handle. The waveform should respond instantaneously.
ECT: using a thermometer to gauge actual coolant temp, the signal back to the PCM should start closer to zero and increase smoothly as coolant warms. It should not exceed 5v.
EVP: Ford likely has a particular procedure, but watching the signal, a smooth change should occur in the signal voltage as the EGR valve diaphragm is operated by hand (assuming you can get a finger in? And wear a leather glove if it's hot.) Note that opening the EGR valve manually at idle should cause an idle drop and possibly stalling.
I believe that DTC 25 indicates a failure to respond during "self test" type routine, 34 indicates an "impossible" voltage for a closed EGR, and 51 is an open ECT circuit. Given this, I would sooner check to see if parts of the wiring harness have been cut, chewed on by a rat, etc., before poking at the sensors themselves.
On Sun, 19 Oct 2003 12:04:47 -0600, jim wrote:

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Taurus 3.0 ( not SHO ) did not have a knock sensor, so that is an invalid code ignore.

93 has a PFE so again the code description is A:) Not valid B:) Misunderstood. The code is most likely misunderstood, what it means is that the sensor voltage is higher or lower than expected. Could be the EGR not opening far enough, or too far. Could be that it is not closing when the processor commands it. The PFE hose could have a leak in it's sense hose causing a false signal. The code does not mean the sensor is at fault, only that the signal is out of range.

Was the engine fully warmed before the test was run? If not nothing wrong. If the engine was fully warm could be the engine is not getting hot enough fast enough for the processor ( possible bad thermostat ). The code does not mean the ECT is bad, only that it is reporting a cooler than expected coolant temp.

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