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No o2 sensor data

fyrfytr33

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'98 Explorer, 4.0L OHV
So I have a 1998 Ford Explorer, 4.0L OHV (VIN X) with 129,000 miles. CEL came on and the idle got rough. Had the codes checked and came up with P0171 and P0174, lean bank 1&2. I replaced the upper and lower intake gaskets as well as the EGR o-ring. While I was in there I cleaned the intake plenum, replaced spark plugs, rebuilt the fuel injectors and replaced the o-rings.
When started I found it had a bad miss (fixed by hooking the spark plug wires up correctly) and the lean codes returned. I found the DPFE was melted and replaced it and the hoses to the manifold. Reset the codes and started, the miss was gone but the idle remained rough and the CEL came back with the same codes. Ran a data capture and noticed I get 0.0vdc from all three o2 sensors and -100% fuel trim on both banks and both long and short term trim levels. Checked resistance of the o2 sensors and continuity from the PCM plug to the sensors, all seemed in order.
Any ideas where to look?
Started checking other components;
PCV Tests good
O2 sensors B1/S1 4.6ohms @60* F
B2/S1 4.2ohms @60* F
Post Cat Sen 4.2ohms @ 60* F
MAF Term A to grd 12vdc
Term B to pos 12vdc
Term C to pos 12vdc
Term D to grd Fluctuates w/RPM 700-4000rpm .80-2.50vdc
TP sensor .94vdc @ idle 4.73vdc @ WOT
IAC valve Tests good
IAT sensor Tests good
ECT sensor Tests good
Fuel pressure KOEO 36psi
KOER 30psi
KOER press reg vac removed 38psi
KOEO 30 min leak down 38psi
Intake vacuum
EVR solenoid Possibly not working No vacuum pump
EGR valve Possibly not working No vacuum pump
So I replaced the plug wires, put the original injectors back in, double checked all connections, put clamps on some vacuum lines, double checked intake stud torque. Warmed up the engine and hooked up the computer and reset the DTC. Seems to be idling better but not perfect. No new codes as of yet.
But I’m perplexed by the fact I still get 0.0vdc from all three o2 sensors and -100% fuel trim on both banks and both long and short term trim levels. It remains in closed loop which I believe is what it should do when warm.


Things still to check;
Fuel cap
EGR valve
EVR solenoid
CANP solenoid
CMP sensor
CKP sensor
VS sensor
Now where do I go?
 
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2000StreetRod

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signal return

Check for continuity from the orange wires on the O2 sensors to PCM pin 91 (gray/red wire) or the TPS gray/red wire if that's easier. There is a splice that connects the O2 sensor signal returns to the other sensor returns.

Do you have any O2 sensor heater malfunction codes?
 
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fyrfytr33

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I checked continuity from the PCM to the connecter at the sensors. Both signal and return wires. Everything tests good. Sensors are within spec. I wouldn't think they were all bad at once, but maybe. Anything else you can think of?
 
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2000StreetRod

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O2 heater codes?

I checked continuity from the PCM to the connecter at the sensors. Both signal and return wires. Everything tests good. Sensors are within spec. I wouldn't think they were all bad at once, but maybe. Anything else you can think of?

Are you saying that you have continuity from PCM pin 91 to each O2 sensor orange wire? I agree it is very unlikely all three O2 sensors went bad. Have the O2 sensors ever worked? It is more likely their common return is not connected. Since the TPS works it's common return is connected to pin 91. That's why I suspected the splice connection.

You never responded about O2 heater codes.
 
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fyrfytr33

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I did check the wires from the PCM plug to the o2 sensor plug. But I see what you're saying and I think I should re-check the wires. I don't know if the o2 sensors ever worked but I've never had CEL on until this started. They could of been de-commissioned by the previous owner. I won't be able to get to it until Friday. Thanks, keep on thinking of anything else.
 
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2000StreetRod

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closed loop?

I don't understand how the PCM could go into closed loop without the precat O2 sensors being functional. Closed loop means that the PCM is continually varying the air/fuel ratio from slightly rich to slightly lean and back as reported by the O2 sensors. I seem to remember that the torque converter will not lock up unless the PCM is in closed loop. How are you determining that the PCM is in closed loop?
 
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fyrfytr33

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OK heres an update from Friday. I rechecked continuity, in fact I checked at the PCM plug pin 91(gray/red) to pin 60(gray/lt blue), pin(87(red/black), and pin 35(red/lt green), all had continuity at about 4.6 ohms. Appears there are no breaks in the wires. I removed the o2 sensors one at a time, hooked up a volt meter set to milli-volts and heated them with a propane torch, voltage rises with heat and lessons when cooling. So it appears they are working but my OBD II is not reading them, or my PCM is bad. While there I checked the injector resistance and they all read 15.7 ohms across the board, checked at the PCM plug. So I realized I had not reset the stored trim levels, unless unhooking the PCM plug would do it (I think it gets its power from the plug so it would) and I unhooked the battery for an hour. Drove it last night no check engine light idling better, we'll see.
When I had the OBD II hooked up with the engine off it says it is in open loop, after running awhile it goes into closed loop.
Next step I think I'll run by AZ and see if their scan tool will read o2 sensor data.

Any other ideas?

Thanks to you all. You are a great help in diagnosing as well as teaching the principles of EFI.
 
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wht2wd50

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had almost the same problem, an found out that the ecm was bad need to find somewhere that can run a diag. on the ecm by itself..
 
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wht2wd50

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and also unplugging the pcm, makes it (forget) everything, after putting some miles on it the cel will come back along with the rough ideal, try the cps mine when bad on my 5.0 and it started running like shit throwing all kinds of codes...
 
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fyrfytr33

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Yeah. That's what I'm thinking. Thanks
 
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RickOTR

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OK, dumb question. What kind of code scanner are you using to check the codes. I have an Actron 9145 but it did not read the fuel trim from the o2 sensors. Fuel trim was -100% on all sensors whether in open or closed loop. Called Actron and they said it was a known software problem and that I would need to get one that was Ford specific.
 
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fyrfytr33

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So I broke down and took it to a professional they hooked it up to a Snap-On Solus Pro scan tool. Everything checks out fine. Fuel trim and o2 sensors reporting data and within spec. So at this point I think I was chasing a software issue more than a auto issue. Thanks again for everyones help. If anything else crops up I'll post it.
 
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fyrfytr33

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Oh, and I was using an OBDCOM scan tool(software) hooked up to a HP Pavillion dv9000.
 
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RickOTR

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Glad to here everything went well for ya. I've seen a few reviews on youtube about the Snap-On Solus Pro scan tool, however, $4,000 is a little steep for this weekend mechanic...
 
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2000StreetRod

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Good call!

OK, dumb question. What kind of code scanner are you using to check the codes. I have an Actron 9145 but it did not read the fuel trim from the o2 sensors. Fuel trim was -100% on all sensors whether in open or closed loop. Called Actron and they said it was a known software problem and that I would need to get one that was Ford specific.

I should have remembered the problem you had and asked about it. I'm glad that you posted and that the issue is resolved.
 
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greasemonkeync

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o2 sensors

I have the same problem no voltage to o2 and-100% fuel trim
What did you do to fix
 
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budwich

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get a new vehicle... :) if you follow the thread, he did nothing other than take the vehicle in to a pro who used a "pro system" and everything checked out fine. Numerous posts about various vehicles having "data issues" ... alot around 97/98 IIRC.

what problem are you actually chasing???
 
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greasemonkeync

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Runs rough at idle and my scan tool says 0.0v to o2 sensors and all of the fuel trim are-100%
I found a junk yard ecm for $50 i will put in tomorrow and see what happens
 
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fyrfytr33

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No o2 data

So to answer your question. I did figure it out. I found my problem to be the OBD II software I was using did not recognize the data. My 98 Ex was from Canada and apparently they didn't all comply to the USA OBD II spec. After chasing all the wires looking for breaks or grounds, testing all the sensors and finding them working, I took it to a local shop to ask them what they thought. They hooked it up to the 'expensive' OBD II device and found there was no problem. Everything was working as it should, values within normal ranges and flucuating as they should. A slightly rough idle is normal and mine sounded better than most. I think more often than not it will be a sneaky vacuum leak somewhere. Common around intake manifolds.

Hope this helps,

fyrfytr33
 
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Acobra68

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No o2 data

So to answer your question. I did figure it out. I found my problem to be the OBD II software I was using did not recognize the data. My 98 Ex was from Canada and apparently they didn't all comply to the USA OBD II spec. After chasing all the wires looking for breaks or grounds, testing all the sensors and finding them working, I took it to a local shop to ask them what they thought. They hooked it up to the 'expensive' OBD II device and found there was no problem. Everything was working as it should, values within normal ranges and flucuating as they should. A slightly rough idle is normal and mine sounded better than most. I think more often than not it will be a sneaky vacuum leak somewhere. Common around intake manifolds.

Hope this helps,

fyrfytr33
My 98 explorer runs fine but tried 4 different scan tools all have no reading on O2 sensors and will not go into O/D can't get ready codes from O2s
 
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