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No voltage from ANY o2 sensors

fyrfytr33

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'98 Explorer, 4.0L OHV
So I have a 98 Explorer, 4.0L OHV, VIN X (from Canada), 130,000 mi. Rough idle CEL on and off for a few months. So found a vacuum leak under the air plenum changed the intake gaskets, rebuilt injectors, new plugs. Still rough idle. Checked the IAT sensor, no continuity, replaced. Still rough idle, hooked up my OBDII again and read the codes. P0171, P0174, P0113, P0122, P1504, also, no voltage from any of the o2 sensors. And the fuel trim in all levels is -100%. Checked fuse #6 as the manual says it is for the o2 sensors, no fuse? Replaced the fuse, still no voltage from the sensors, fuel trim unchanged.
Any other ideas? I'm thinking maybe a wiring issue, PCM, all o2 sensors bad. I need some direction here, thank you in advance.
 


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vroomzoomboom

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ground wire not hooked up?
 




fyrfytr33

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Could be. Any idea where to start looking?
 




jman

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Don't bother looking for a fuse for the 02 sensors. They do use a fuse for the heater circuit (to get them to start working sooner) and the computer controls the on/off of the heater. As far as the voltage the computer uses from the 02 sensors, its anywhere from 1mv to 900mv, however the 02 sensors make there own voltage once heated (or start to heat up), there isn't a supply like a the 5 volt ref voltage too say a TPS or IAC or DPFE. Get the engine up to full temp and then check the data for the o2.

I would check main harness connections, do a wiggle test of the harness (be mind full of moving/hot parts) look for an loom or harness that can rub and maybe be cut.

Worst case computer issue.
 




budwich

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you will need to dig into your wiring and likely need a wiring diagram (references to wiring can be found here ... posted by bob flood)... anyways, potentially you disturbed a splice / broke a connection on the signal return for those sensors... maybe. some of those travel in/around the injector area which you disturbed. Having said that, were there codes before you started your "adventure" / maintenance work?

Having said that, it would appear you have access to a code reader / data grab.... if so, take a look at your o2 sensor data if you have "live data" capability.
 




fyrfytr33

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Yes there were codes prior to my adventure, hence the gasket replacement. Before I was getting P0171 and P0174, this was the start of my adventure. Tomorrow I can start chasing the wires. I drove it for 20 min and checked the codes and still no voltage. It is possible they are all bad. Or a previous owner unhooked some wires. I was hoping maybe someone had come across a similar problem and could point me in a specific direction.

PCV good
replaced IAT sensor
replaced upper and lower intake gaskets
replaced fuel injectors
And more I can't ID right yet
 




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budwich

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I believe that if your O2 sensors are not "creating" any voltage then you would be getting a code for "o2 sensors not switching" which you are not so I think you are chasing the wrong "symptom".
 




fyrfytr33

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All good points. I'm not sure how you aquire your knowlege but it is awesome! So I have some new direction for the day. I'm still a bit confused as to why there is 0.0v from the o2 sensors after warmed up. Also the fuel trim is at -100%. Unless a wire or all sensors are bad. This is from a data log I ran after I replaced the IAT sensor and drove for 20 min. Something is not right.
 




budwich

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on my "free logger" that came with the elm interface for the computer, the logger shows how the voltages "toggle" or switch back and forth as the o2 sensors go "in and out" of "oxygen detection levels". I am thinking maybe you have injector issues maybe... but that is pure guess based on the -100% trim which to me indicates it is trying to reduce fuel input. Hopefully, some one else might give you another suggestion.

Further, as someone suggested, have you check to see that your heater voltages are there and have you check that there are grounds associated accordingly?
 




fyrfytr33

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More help

So I traced all the wires from the PCM plug to the o2 sensors. Continuity on all wires:). Checked the o2 sensors, they all were from 4.2-4.6 ohms. Runs ok but idles rough. Didn't have time to run another data log. The CEL came on again. So I wanted to run this by everyone,


I found this info on this site and need to make sure of something.

"They should be 19lb/hr injectors if I'm not mistaken. (19.5 technically )

All of the Bosch/Ford injectors are color coded, but make sure they send the right size/fitting which sounds like they are...

Gray- 14lb/hr
Yellow- 19lb/hr
Blue- 24lb/hr
Red- are 30lb/hr
Green- 42lb/hr
Browns~ 70 lb/hr, but not positive."


So I have a 1998 Explorer, (Canada edition), 4.0L OHV vin X. about 130,000 mi. I changed the intake gaskets recently and have been having problems since. While I was in there I rebuilt the injectors. Ended up with a miss. Bought some rebuilt injectors...still had a miss. Further checking and I found I'm stupid (#4 & #6 wires switched.)
So here is my question; The injectors I took out were red, the rebuilt ones were yellow. The guy who rebuilt them said they were the same, but seeing this I'm not sure. What errors would this produce? Lean condition? I guess I should put the old ones back in and run another data log.
Please let me know what you think.


OK, so what are your thoughts? Is this as simple as putting the old injectors back in. I already rebuilt them. I only replaced them as I was told they must be the cause of the misfire.

Thank you for any help,

Mike
 




fyrfytr33

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Closed loop

So I was thinking. If the PCM is running in closed loop would it block the o2 sensor and fuel trim info from getting into the datalog? I see I'm getting resistance from the water temp sensor, the hotter it got the lower the resistance was, around 110ohms. So if the thermostat was out of spec could it be telling the PCM it was not yet warm and stay in closed loop. Any other ideas along this line of thought?
 




2000StreetRod

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30 pound injectors

. . .
"They should be 19lb/hr injectors if I'm not mistaken. (19.5 technically )

All of the Bosch/Ford injectors are color coded, but make sure they send the right size/fitting which sounds like they are...

Gray- 14lb/hr
Yellow- 19lb/hr
Blue- 24lb/hr
Red- are 30lb/hr
Green- 42lb/hr
Browns~ 70 lb/hr, but not positive."


So I have a 1998 Explorer, (Canada edition), 4.0L OHV vin X. about 130,000 mi. I changed the intake gaskets recently and have been having problems since. While I was in there I rebuilt the injectors. Ended up with a miss. Bought some rebuilt injectors...still had a miss. Further checking and I found I'm stupid (#4 & #6 wires switched.)
So here is my question; The injectors I took out were red, the rebuilt ones were yellow. The guy who rebuilt them said they were the same, but seeing this I'm not sure. What errors would this produce? Lean condition? I guess I should put the old ones back in and run another data log.
Please let me know what you think.


OK, so what are your thoughts? Is this as simple as putting the old injectors back in. I already rebuilt them. I only replaced them as I was told they must be the cause of the misfire. . . Mike

With 30 lb injectors (red) more fuel will be injected than stock each time the injector opens. The O2 sensors should detect the rich mixture and report it to the PCM. The PCM will try to reduce the rich condition by changing the fuel trims. When the pre-established criteria for short and long term fuel trims is reached the PCM should report a diagnostic fault. In your case it should be:

P0172 System too Rich (Bank 1)
P0175 System too Rich (Bank 2)

The person who sold you the 30 lb injectors is either ignorant or just wanted the sale. Those injectors are suitable for a forced induction engine with a custom tune.
 




budwich

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couple questions... are you quoting freeze frame data (associated with the dtcs) or live run data? You likely need to look at run data.
 




fyrfytr33

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Not freeze frame, live data stream. Did some checking and found the injectors I bought were not for a 4.0l. Replaced the rebuilt originals, I don't think this is the idle problem but it could explain the excess fuel consumption. Tomorrow I'll put things back together and see what happens. To be continued.....
 




Ausipitator

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no voltage

I realize that this is an extremely old thread, but Im having the exact same issue of no voltage from any o2 sensors and -100 fuel trims. ive replaced the upper two sensors with new units to no avail. any feedback from the original poster?
 








robertn78

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no voltage

I realize that this is an extremely old thread, but Im having the exact same issue of no voltage from any o2 sensors and -100 fuel trims. ive replaced the upper two sensors with new units to no avail. any feedback from the original poster?

I am having this issue too. I am using an elm scan tester. Other cars show voltage in the Torque app. I have a 1998 4x4 4.0 and it shows 0V. I have replaced all 3 O2 sensors (2 upstream and 1 downstream). Easier job than I thought but still 0V. I have a digital multi meter and can test out of the O2 sensor. If I get a voltage out of the sensor, why is the ECU not seeing it? I doubt all 3 sensors are bad.
 




2000StreetRod

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If the PCM is going into closed loop then it is reading the O2 sensors and the problem is that your scanner doesn't support your vehicle. Try reading short term fuel trims. If they cycle between slightly lean and slightly rich then the PCM is using the O2 sensors to control the AFR.
 


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Same problem after replacing fuel injectors and intake gaskets. Codes lean banks 1 and 2 And both heated o2 sensors. Had it smoke tested and egr valve was leaking.fixed it but still have same codes put new fuel pump on it checked fuel pressure 63lbs. About everything is new even catylitic converters. Had ford do a new download hoping that may help. Dealership can not fix it. 2001 sport trac.
 




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