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O2 and Emission Codes nightmare - 3 years running

Templars83

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2000
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Ford Ranger
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Forgive the long post - thank you.

Thank you for accepting my request to join the forum. I am at my wits end over a long standing problem I'm having with my 2000 2.5 5speed Ranger, that has served me very well. I have been getting a persistent check engine light over emissions. As a result I cannot pass emissions and my plate is now sitting at 2018, and has been parked quite a bite until recently.

Prior to all this it had been running very well, and was getting 25 mpg on an almost bullet proof engine. Plugs and coils were replaced before that as well as the fuel pump.

Out the blue, I started getting the CEL and forever since, I've been getting mostly emission codes such as EGR and EGR solenoid and others. I've changed the EGR valve, the EGR vacuum solenoid, and DPFE sensor. I have taken the upper intake manifold off and cleaned all the passages thoroughly. STILL the codes came. I recently was forced to drive it 1000 miles. The literally 10 mpg I had on that trip, has me determined to try ONCE again to resolve the issue.

Based on the latest codes:

P0133 O2 sensor Circuit Slow Response


P0401 - Exhaust Gas Recirculation Flow Insufficient (this is the code that hasn't gone away ever)


First thing I did was run a bypass hose from the EGR valve solenoid directly to the EGR valve WHILE running. It will stall it which tells me the flow is there and the Valve is opening - therefore no carbon issue in the intake manifold. This leads me to think bad DPFE sensor once again. I decided to do one more thing first. Knowing they hadn't been replaced in forever, I bought 2 Bosch O2 sensors and hoped this would help things especially with mileage.
After fighting one of the sensor's having to go through the fenderwell, I replaced them today (Amazon promised Friday - they came today - prime guarantees mean nothing. Additionally, I did a little vacuum test on the EGR valve which caused it to want to stall - thus clear flow there - where is this p0401 coming from forever?

Good pep at first - and the engine is running strong as it always has, even with all these issues. 40 miles later, CEL light is back and it's throwing these codes:

P0136 O2 Sensor Circuit (2 brand new Bosch sensors SO WHY AM I GETTING THIS)

P0401 Exhaust Gas Recirculation Flow Insufficient AGAIN

(Pending) P1131 O2 sensor related - possible lean condition and other things but O2 is first listed (SO i AM GOING LEAN VS RICH NOW???)


In the past, the engine was running rich for sure - thus the 10 mpg on that last trip. I could occasionally smell the gas.

So I am now thinking DPFE sensor or maybe the wiring is an issue from the O2 sensor - maybe - and will look at that tomorrow. It seems I am looking at 2 issues or maybe only one, and the very old O2 sensors weren't a problem afterall. I don't know what to do with the p0401 as I have changed everything about the emissions or just about. Perhaps I had a bad DPFE sensor part to begin with. Again, this is a long running issue that has me lost and frustrated.

Is there some sort of ECU reset or anything I am missing? Any ideas or thoughts would be greatly appreciated. Sorry for the long but informative post.

Craig
 
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mlkary

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Have you checked or replaced the coolant temp sensor. They get biased and can cause a rich or lean condition just as an o2 sensor can do. They are like a rehostat and change voltage as the coolant warms up. They go bad just like a light dimmer switch that developes bad contact spots. Sometimes they cause a rotten egg smell from the exhaust but mostly on GM. Look for coolant in the wiring if sensor is leaking through the terminals. This can cause liquid coolant to be found in the ecm. Check voltage in the cooling system with vehicle running.... Less than half a volt. Put volt meter on low volts and ground negative probe. Take positive probe an insert into coolant in radiator without contact to any thing else. Over 0.5 volts replace coolant. This will also dissolve solder in heater cores.
 

Eddo Rogue

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+1 on the coolant temp sensor. Also it could be a bad brand new DPFE, is it a motorcraft or otherwise oem brand? Parts are crap these days. I had this issue with my IAC valve. The new autozone brand was no good, I ordered an oem unit online and it worked. Also a bad alternator brand new (not rebuilt). I would re-replace your parts with OEM units.

Last thing you might have an intake leak or some other vacuum/purge issue. Usually O2 sensor is not the problem, it s just reading one and therefore throws a code.
 

felgar_1

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farmington, il.
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2000
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ford ranger
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2WD
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2" on the 2000
Total Drop
6" on the 99
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255/45r18
My credo
drive like you stole it
make sure your hoses and the ports on the dpfe are clear they like to plug up. ether use a scan tool to clear the ecm or unhook your bat and turn the key on should clear them, also make sure your grounds are clean they can cause alot of faults too,
 

bills4065

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The first thing I would try in your situation is hook up a scan tool and set up these 3 pids only: 1)system status 2) Bank 1 Sensor 1 and Bank 2 Sensor 1. Warm up the vehicle on a drive and then monitor the voltage on the upstream sensors at wide open throttle, they both should be over 800 millivolts on both banks at wide open throttle , as every gas vehicle runs rich at wide open throttle. The system will drop out of closed loop at wide open throttle that is normal. I have a passenger with me to monitor scan tool any time I do this test, to be safe. I usually go from first to fourth and then "peddle to the metal. " It all happens pretty quick. That would be what I would try, to get some direction.
 

RobbieD

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Toonces drives a Ranger . . . . just not very well.
For what it's worth, I've never had an aftermarket DPFE sensor last more than a few months at best. That is one part that I will bite the bullet on, and only use Motorcraft as the replacement.
 

19Walt93

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If you don't have time to do it right will you have time to do it over?
We used to change a bunch of DPFE sensors and almost all set P0401 codes. I'd inspect the hoses carefully and use a Motorcraft sensor. DPFE is delta pressure feedback EGR if you care.
 

Eddo Rogue

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Ranger 4x4
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4.0 V6
Engine Size
OHV
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Manual
2WD / 4WD
4WD
Total Lift
skyjacker front leveling kit
Tire Size
31-10.50R15
My credo
Crossed threads are tight threads.
We used to change a bunch of DPFE sensors and almost all set P0401 codes. I'd inspect the hoses carefully and use a Motorcraft sensor. DPFE is delta pressure feedback EGR if you care.
+1 on the Motorcraft.
 

felgar_1

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Location
farmington, il.
Vehicle Year
2000
Make / Model
ford ranger
Engine Size
2.5 and 3.0
Transmission
Manual
2WD / 4WD
2WD
Total Lift
2" on the 2000
Total Drop
6" on the 99
Tire Size
255/45r18
My credo
drive like you stole it
i got rid of mine along time ago.
 

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