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KOEO test

Mikecraig80

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Having trouble with my 94 4.0 . Idles rough (when it runs) and when I ran codes recently I got 114, 116, 335, 715 and 815. The first two I believe are because the engine was cold ( won't start). But I have replaced the plugs, wires, coil pack, Crankshaft position sensor and tested the ignition control module. Any ideas?
 
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MrShorty

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KOEO 335 points to a problem with the EGR's DPFE sensor -- which seems to be a fairly common problem. I would quickly inspect the wiring to the DPFE, the replace the DPFE is there is no other obvious problems.
 
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Mikecraig80

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KOEO 335 points to a problem with the EGR's DPFE sensor -- which seems to be a fairly common problem. I would quickly inspect the wiring to the DPFE, the replace the DPFE is there is no other obvious problems.
Okay , where is the dpfe sensor?
 
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2stroke

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A bad DPFE wont cause a no start. Are you sure you got codes 715 and 815? I can't find anything on them. I think the ECM is worth looking into. Open up the metal case and look at the board for leaking capacitors or other bad components.
 
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Mikecraig80

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A bad DPFE wont cause a no start. Are you sure you got codes 715 and 815? I can't find anything on them. I think the ECM is worth looking into. Open up the metal case and look at the board for leaking capacitors or other bad components.
okay, getting frustrated here, where is the ecm located?
 
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Centaurious

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ECM is located behind the passenger plastic kickpanel in front of the door.
 
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Mikecraig80

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Got it out and opened, no obvious damage, very light "dust" on C 7 which I assume is a capacitor. (For what it is worth I was trained in electronics in the Navy)
 
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Mikecraig80

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Got it out and opened, no obvious damage, very light "dust" on C 7 which I assume is a capacitor. (For what it is worth I was trained in electronics in the Navy)
Replaced dpfe and still won't start. Get codes 114, 116, and 159.
 
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Centaurious

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All three of those codes are for sensors out of range.

114 Intake Air Temperature
116 Engine Coolant Temperature
159 Mass Air Flow sensor

Before you start spending money on new parts please do these simple voltage checks. One sensor with a code is probably a bad sensor. Multiple sensors tend to indicate a common cause, like a bad ground.

Battery (+) to Battery (-). This establishes a reference voltage. Must be on shiny spots in the Posts not the Clamps.
Battery (+) to Vehicle Chassis. This should be a spot on the firewall that is free of paint and has shiny metal. Ideally this should be the same as reference voltage or only a few tenths of a Volt less. If it is more than a few points less you have a bad Battery to Chassis Ground.
Battery (+) to Engine. This should be on the top Alternator Bolt after a clean spot is scraped or filed. Again, should be reference voltage or a few points less. More indicates a bad Battery to Engine Ground.

You can test from Battery (-) to various (+) terminal connections to check the Positive Battery Cable.

I suggest the above test because the battery cables are a known trouble point for the Explorers

If the above checks are good you can check the Voltage at the MAF. The MAF is a three wire sensor with (+) and (-) on the outside terminals and a variable positive voltage from the center terminal. If testing the (+) and (-) of either the MAF or the TPS does NOT indicate reference voltage or near to it the ECU has a bad ground or positive voltage problem.


A bad DPFE will not keep the engine from starting but it will run rough. I hope you got the Wells/Airtech DPFE sensor from Autozone. I had one from O'Reilly's that was replaced 4 times in a month and half till I got a refund.
 
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Mikecraig80

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All three of those codes are for sensors out of range.

114 Intake Air Temperature
116 Engine Coolant Temperature
159 Mass Air Flow sensor

Before you start spending money on new parts please do these simple voltage checks. One sensor with a code is probably a bad sensor. Multiple sensors tend to indicate a common cause, like a bad ground.

Battery (+) to Battery (-). This establishes a reference voltage. Must be on shiny spots in the Posts not the Clamps.
Battery (+) to Vehicle Chassis. This should be a spot on the firewall that is free of paint and has shiny metal. Ideally this should be the same as reference voltage or only a few tenths of a Volt less. If it is more than a few points less you have a bad Battery to Chassis Ground.
Battery (+) to Engine. This should be on the top Alternator Bolt after a clean spot is scraped or filed. Again, should be reference voltage or a few points less. More indicates a bad Battery to Engine Ground.

You can test from Battery (-) to various (+) terminal connections to check the Positive Battery Cable.

I suggest the above test because the battery cables are a known trouble point for the Explorers

If the above checks are good you can check the Voltage at the MAF. The MAF is a three wire sensor with (+) and (-) on the outside terminals and a variable positive voltage from the center terminal. If testing the (+) and (-) of either the MAF or the TPS does NOT indicate reference voltage or near to it the ECU has a bad ground or positive voltage problem.


A bad DPFE will not keep the engine from starting but it will run rough. I hope you got the Wells/Airtech DPFE sensor from Autozone. I had one from O'Reilly's that was replaced 4 times in a month and half till I got a refund.
My maf is four wire but measures very close to the reference voltage as the other voltages are within the reference and the dpfe has been replaced.
 
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Centaurious

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Great! That means you don't have a Primary Electrical problem and the ECU is receiving and sending the correct voltages. The Intake Air Temp Sensor and the Engine Coolant Sensor shouldn't keep the engine from running. I'm sure someone has posted the tests for the MAF but I don't know them. Searching the forum is your best bet. I hope the MAF tests bad as it's easy to swap out.

I appreciate your running the tests as I find the people who throw parts at a problem hoping for a fix to only be slightly better than those who throw money in a bonfire while praying for the gods to repair it.

When I get stumped I always remember Fuel, Spark, Compression, and Timing. The cornerstones of a combustion engine.
 
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natenkiki2004

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The engine should start and run with the MAF disconnected (I've done it), same with the other sensors. If it runs noticeably better, I'd try to find a MAF from a junkyard and buy new IAT and ICT sensors.
 
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2stroke

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I am under the impression your engine will not start at all, so I don't think any of those sensors are the cause. An IAT has a pretty minor impact, and the engine will start without a MAF or coolant temp sensor, although it would probably run poorly. If your engine does start, please correct me. I would definitely test your fuel pressure. Its a very easy test, and in my experience, fuel problems account for 90% of engine running problems or better.
 
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Mikecraig80

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I am under the impression your engine will not start at all, so I don't think any of those sensors are the cause. An IAT has a pretty minor impact, and the engine will start without a MAF or coolant temp sensor, although it would probably run poorly. If your engine does start, please correct me. I would definitely test your fuel pressure. Its a very easy test, and in my experience, fuel problems account for 90% of engine running problems or better.
Fuel pressure test was @34 psi, a little low (35 - 45 recommended).
 
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2stroke

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34 psi is fine, I've seen them run ok with mid 20's for pressure. Assuming you have good spark, that only leaves compression and timing. How did the old spark plugs look when you replaced them?
 
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Mikecraig80

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Plugs looked alright but replaced them anyway. By the way, still getting codes 114, 116 and 159. And no, it will not start.
 
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natenkiki2004

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Plugs looked alright but replaced them anyway. By the way, still getting codes 114, 116 and 159. And no, it will not start.
Did you try unplugging sensors, specifically those listed in the codes? Might be that one is shorted or sending a horribly wrong signal.
 
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2stroke

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I suppose anything is possible, but the engine should theoretically be able to run with nothing but the crank sensor. Can you be more specific with the spark plugs? What color was the electrode? Any build up? Carbon on the threaded base? Its getting late now, but tomorrow I'll dig into my EVTM and see if I don't notice anything to connect all three of those sensors. I'm guessing you already confirmed there is spark at the spark plugs. A quick test would be to spray some starting fluid into the plenum and see if it starts.
 
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natenkiki2004

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I suppose anything is possible, but the engine should theoretically be able to run with nothing but the crank sensor. Can you be more specific with the spark plugs? What color was the electrode? Any build up? Carbon on the threaded base? Its getting late now, but tomorrow I'll dig into my EVTM and see if I don't notice anything to connect all three of those sensors. I'm guessing you already confirmed there is spark at the spark plugs. A quick test would be to spray some starting fluid into the plenum and see if it starts.

It's rare but if the 5v reference is shorted either in the wiring or the sensor, it will kill the system. Shouldn't kill the computer but it will be clueless as to what's going on. From reading above, you have 12v in various places but the sensors in your codes run on 5v. Check for that just to make sure.

I'm going to second 2stroke's request for checking for spark. I don't see that mentioned in this thread. If you don't get spark, check and see if your RPM gauge goes up at all when cranking. If both are "no" then you need to look at the crank sensor.
 
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