EGR problem diagnosis

MY daughter has an 01 Ford Ranger 4 cylinder that failed the Maryland emisions test. The "check engine" came on about a week before the test and the emisions tester said the trouble code was P1401 which is "differential pressure feedback electronic sensor circuit high voltage".

I under stand that may be EGR related. I found there is no vacuum at the ERG valve when I increase RPMs while parked. I traced the vacuum line from the EGR to what I think is called the EGR control valve. It has another vacuum line from the intake manifold and a two connector plug. The two connector plug has 12 to 13 volts present across the two terminals of the plug. I took a reading while unplugged from the control valve and while connected and at idle and under increased RPM's but still always get 12-13 volts.

One more thing. I disconnected the vacuum line from the EGR while at idle, connected a spare piece of hose to the valve and sucked on the other end of the hose and the engine stalled, so it looks like the EGR itself is working but not getting vacuum.

Is there any other way to test the EGR control valve? Shouldn't the voltage change when RPM's increase so that it will allow vacuum to get to the EGR? Am I way off on this and should be looking at something else?

sounds like the egr is working.
as to the voltage question, the pcm controls ground to operate the
egr control solenoid. it should read battery voltage through the solenoid
because there is no ground until the pcm commands egr operation.
to make the pcm command egr operation, some load is required, engine
at operateing temp, and light cruise. it is probabaly just the flow sensor
2 hoses and 1 electrical connector, aluminium in color.

Thanks. The flow sensor appears to be on the right side near the back of the motor...looks like the hoses are arranged as a by pass going from the intake to exhaust manifolds? There is one electricl plug on the aluminum hpousing which is about the size of a pack of cigarettes.

So this air flow sensor would cause trouble code 1401 "Differential pressure feedback electronic sensor circuit high voltage" and caused the truck to fail the emissions test?
After several weeks of being "on" the check engine light is now off. Any clue? Do you think the light being on was even related to the air flow sensor?

been reading other forums and posts, seems carbon in the egr tubes, passage ways etc is a real problem on fords. Might be worth looking into before you pull your hair out

good luck and keep me postted if you wish

jeff

I recently had the same proble with an 01 sable problem turned out to be the
egr sensor you spoke about by the firewall.When i pulled it off a small amount of water came out.as soon as i replaced it light went out i was getting the p0401 excessive egr flow.

Ford has recall out for codes P0401, P0402, P1400 and P1401 that states to replace the DPFE sensor if any of these codes are present.