I have been trying to debug an engine code 335 problem on my 94 ranger 2.3L 5speed. It indicates a DPFE sensor problem (EGR (PFE) sensor voltage out-of-range).

When I performed a KOEO test, I got this 335 code. I checked the wire to the DPFE sensor, 5V was present. There is no check engine light when the car is running.

Please advise.

 

If there is no CEL(check engine light) then 335 was just a temp code that the computer set at some point and if repeated a few times it will turn on CEL with 335 as a memory code

The computer doesn't set a code lightly, especially "out of range" codes, because they can be erroneous, a temporary voltage drop that's not repeated over several more drive cycles and it will clear itself if not repeated

Wait for CEL to come on, which may take a few drive cycles, EGR is only used after engine is fully warmed up, and then see what the code is, computer can change its mind too, might be a different EGR code that it settles on

Check the hoses on the DPFE sensors as well, no breaks or cracks

 

Thanks RonD. I will just monitor it for now. I use the truck every day and it starts right up and runs smoothly with no issues. Btw, is there a way to clear this temp code without disconnecting the battery cable (neg)?

 

Yes, if you do the setup to read the codes again then when the 335 code is being sent disconnect the Self Test jumper wire or if using a handheld unit release the test button, that will clear just the codes, its not a full reset like disconnecting battery does

 

Full reset doesn't clear the temp code 335. Those 2 hoses have no breaks or cracks (they were replaced 2 years ago), however, the DPFE sensor is 27 years old ... lol. Please advise.

 

Full reset doesn't clear the temp code 335. Those 2 hoses have no breaks or cracks (they were replaced 2 years ago), however, the DPFE sensor is 27 years old ... lol. Please advise.

 

Just curious .. when doing KOEO test, I know I get VREF (#3) = 5V and I verify SIG Return (#2) has solid ground. Will Self-Test do any other things to the input voltage (#1)?

 

No, you have to use a hand vacuum pump to test signal wire voltage

Try to blow thru both hoses, key off, they just go to EGR exhaust tube so should be easy to blow thru, the ports can get carbon fouled


DPFE sensors don't usually last that long
Exhaust has water vapor in it(why exhaust systems rust to badly and tail pipe drips water), and that vapor can condense inside the chambers of the DPFE, and that causes failure

 

What will be the normal voltage between pin #1 and pin #2 under KOEO? That should tell me something.

 

I found this online. I should look for 0.45V.

 

Mine is 0.3V ... that's why it's out of range. Lol.

 

Yes, should be .45 to .55v

 

RonD, when the voltage (0.45V to 4.5V) sends to PCM, what exactly it will do to the car. Please explain briefly.

 

???

DPFE voltage back to computer tells it how much exhaust gas is being pulled in thru the EGR valve

.45v to .55v is the "at rest" voltage when EGR valve is closed
After engine warms up the computer will monitor engine load, higher load means higher cylinder temperature so higher NOX emissions(toxic gas), computer adds exhaust gases buy open EGR valve, this causes slower smoother combustion which lowers cylinder temps which lowers NOX emissions

Computer knows the RPMs and throttle position so can calculate how much exhaust to add when needed, it uses feed back from DPFE sensor so it knows how much exhaust is flowing thru EGR valve
But it needs a baseline pressure, which can vary by height above sea level, that's the key on voltage provided by the DPFE's signal before startup

 

New DPFE has been ordered and should be an easy replacement. Thanks again.

 

New DPFE installed, no more code 335. Thanks.

 

Good stuff

Thanks for the update and THE FIX