$25 challenge

[bort]

The 25 dollar challenge. $25 via paypal to the first person with the
correct diagnosis. If you don’t believe me then don’t help, but the
way I see it there’s nothing to lose so all help is appreciated.
Trying to find someone to actually read through what I’ve done and
give it some real thought as my head hurts from doing so, and I’m
nearly out of ideas.

The truck:
97 ford ranger ext cab 4x4, 4.0 vin x, m50d manual trans, BW1354
manual transfer case, 8.8 31 spline exploder rear with discs and
4.10s, 33x12.50s, 330000mi on the truck, 80000mi on the engine.

The problem:
-My O2 sensors all read 0.000, yes all three of them. This is causing
my fuel trims to all read -100.0. The VSS also reads 0 all the time.
-These readings have all been taken live during every possible driving
condition I can create and they have all been on three different
scanners including the stupid expensive snap-on type. I have MIL
indicating lean bank 1 and 2. Understandable considering the sensors.
-The truck runs alright, starts, runs, doesn’t die, and throttle
response isn’t bad. Definitely smells rich though.

What I’ve tested/tried:
-Checked all fuses- all good
-Cleaned MAF- no change
-Checked voltages to MAF, IAT, TPS, Temp sensor- all within range
-Tried 3 different DPFEs I had access to (correct part numbers)- no change
-Checked Voltage to DPFE- within range
-Checked voltages to O2 sensors- (key on) 12.5V in (heater), 2 grounds,
nothing in or out of 4th wire on all 3 sensors
-Replaced one O2 sensor-no change (shot in the dark)
-Borrowed a PCM with matching #s- no change
-Triple checked with multiple dealers that the PCM was correct part
number for the truck. (discovered it’s a 49 state truck)

Conclusions:
Somehow I think I’m losing VREF to the sensors and VSS. My only
remaining ideas are:
-the wiring harness is incorrect for the computer pin connector
-I have an open VREF wire for the sensors. However the VSS and O2s have
different VREF supply based on the wiring diagram.
-I managed to diagnose 3 bad DPFEs. Based on the wiring diagram I
can see how they would mess up the O2 sensors.
-I somehow opened a loop on the lower wiring harness by disconnecting the electric transfercase to put in a manual.

As stated $25 via paypal for the right diagnosis. I should have the
answers to any followup questions, if I don’t then maybe you’re on the
right path. If you come up with the answer on wred or thurs I will tell you but you may have to wait till Friday for me to get paid as this project is expensive.
Thanks, Kirk

 

[RangerSVT]

I don't care about the reward, but check your ecu grounds. What you need is a breakout box for testing. Did you say you have no working speedometer as well? If so, check your plug for the transducer on the driver side frame near the transfer case...

SVT

 

[adsm08]

Ok, lets start with the lack of VSS.

Get the rear wheels in the air, unplug the sensor, and tap into it with a volt meter set to AC voltage. Have someone run the wheels up to speed. It should slowly run up to about 7V AC voltage, if it does not, either the sensor is bad, or it is not getting a trigger.


Now for the engine light. That is a good one. Start by checking for key-on power at the orange wire of the bank one oxygen sensor, DC voltage.

If you have power there, it should only be about 5 volts. If it is good to battery ground, then check voltage against the grey/light blue wire at the sensor plug.

Get some results to those tests posted up and we can go from there.

 

[bort]

"check your ecu grounds. What you need is a breakout box for testing"

Sounds like an idea to me but of the two grounds I know of on the harness next to the box both are good. how to test the box alone I dont know. please elaborate.

"Did you say you have no working speedometer as well?"

Sorry I should have specified, the speedometer does work; however the computer does not show it. While driving the my scanner and two others show the vehicle speed as 0.

"Now for the engine light. That is a good one. Start by checking for key-on power at the orange wire of the bank one oxygen sensor, DC voltage.
If you have power there, it should only be about 5 volts. If it is good to battery ground, then check voltage against the grey/light blue wire at the sensor plug."

Here it goes, key on engine off, O2 sensor1 bank1: I have 4 wires 1)Light blue/orange 12.5v supply from fuse to O2 heater all good. 2)red/white ground for heater good (to connector and through ECM) 3)Gray/light blue I think should be the 5v VREF you are speaking of, but nothing at the sensor or coming out of ECM at pin60 or on the other 2 sensors as well, both at pin35 4)orange (changes to gray/red down the line) common ground with the other sensors, DPFE, TPS,and IAT) all good continuity to pin91, all good ground through the computer.

All of the wire colors and pin numbers have matched the wiring diagram and i cannot find any breaks in continuity except at sensor3 (behind the cat) the heater ground did not seem to ground through the computer.

Thanks for the help guys, keep it coming. I will try more tomorrow night provided I can switch the injectors on a Cummins and study for finals before its too late.

 

[bort]

Other things I for got to mention.

I tried my old ECM, same thing.

(for shits and giggles) I tried a new DPFE, no change.

It has been running closed loop for weeks, but tonight for some reason it went to OPEN2 and ran pretty rough at about 700rpm. I'm not sure if it was me disconnecting and reconnecting stuff to check continuity< but i thought I would add this bit of observation if it points in some other direction.

Could it possibly just be running that lean from a bad pump/filter? I though I would at least see some sort of O2 reading even with that. The lack of 5v reference at the O2's makes me think thats not the case but I'm still learning.

 

[4.0B2]

you're questioning fuel pump...

have you check the fuel pressure?

 

[bort]

No I have not actually checked the psi on the fuel rail, shoots real far though, haha. I'm not really questioning the fuel pump. That was more of a brain dump, I'm kinda shooting at anything that moves now.

 

[RangerSVT]

A breakout box is a device used to check the circuits in and out of the ECU at the ECU...
You say the VSS is operational, but the ECU doesn't see it, and you are having issues with O2 operation. I would look real close at the trans harness connector at the firewall (if the trans harness is part of the engine harness, then check C110 connector, the 42 pin connector near the firewall on top/side the engine). My guess is you have a bad or weak ground connection at that plug. The ground side of the VSS and the grounds for the O2 sensors are shared at this location....


SVT

 

[Runnin'OnEmpty]

...... I tried a new DPFE, no change.

It has been running closed loop for weeks, but tonight for some reason it went to OPEN2 and ran pretty rough at about 700rpm. I'm not sure if it was me disconnecting and reconnecting stuff ......

The C110 connector is the one that's spring loaded with
a bolt securing it, attached to the driver's side valve
cover, right?

Check the bolt for tightness; it might be as simple as
the bolt loosening and opening circuit connections.

If the bolts tight, open the connector and check for
corrosion, etc...

 

[bort]

Sorry been preparing for my last finals of college. Anyway, updates:

My guess is you have a bad or weak ground connection at that plug. The ground side of the VSS and the grounds for the O2 sensors are shared at this location....

Check the bolt for tightness; it might be as simple as
the bolt loosening and opening circuit connections.

C110 connector is all good.

Discovered that the engine had been switched prior to my ownership, looks to be an engine out of an explorer. At least this is what I gather from the wiring harness when I compare it to the chiltons diagram for 96-99 exploders. But its not entirely accurate... explorer has a knock sensor going to pin12 but theres no pin12 on the harness; there is a pin 11 to the purge flow sensor which is not supposed to be on the explorer only on the ranger. On the other hand, O2 bank2 sensor1 connects to pin87, which i do have on the harness is only found on the explorer. On the ranger sensor21 and sensor12 both connect to pin35.

I went through the entire harness checking for correct continuity at all pins based on the wiring diagram. Everything matched accurately except for sensor21. I rectified that but I still have no O2 readings. The computer did go from open(cold start)>closed>closed1. Thats not something I've seen before and not sure what its telling me?

From what I can tell on the diagram Sensor21 and sensor12 receive 5V ref from pin35, sensor11 receives it from pin60 and all ground to pin91 along with: DPFE, TPS, IAT, and coolant temp. Neither pin60 nor pin35 show 5V on two different computers, best
I could get was 0.75V.

To sum it up... the harness matches the diagram to a T but the problem is still there.
My question is, does the computer supply the 5v ref independently(35,60) to each sensor that uses it and collect it through a common(91), or does it supply it through a common(91) and read the returns independently(35,60)? It seems to me that if it supplied 5v through the common at 91 I wouldn't have readings from any of the other sensors.

Another odd observation, according to 3 ford dealers my truck should be a 49 state truck and I have the correct computer(s) for it but when i run my scanner it shows that the OBDII state is California.

For reference, the diagrams I've been looking at are in the Chilton manual for 91-99 ranger/explorer/mountaineer. Unfortunately its the same diagram in the Haynes manual too. I couldn't seem to convince the ford service guy to give me his schematics, gave me some BS about how he doesn't have that. Although it wouldn't surprise me the way they like to throw parts at things till people give up and just stop coming back.

 

[PanamaExpat]

Just started following this. Sounds very interesting. 5 volts is what is called a high or on state in a logic circuit. 0 to about 1.5 is a definite low or off state. If something like a sensor has a dead short it could/would pull the entire leg of that logic circuit to ground and be in a perpetual off state. Have you checked the following: resistance readings through the individual sensors, looked for a pinched or abraded cable that could be shorting Vxx to ground, or since you have stated that this is a SWAP vehicle that someone did not get one of the sensor feeds on the engine harness wired wrong?

ADSM is the electronics controls master on this board. I am just an old school electrical engineer and some of these modern car control circuits are still a bit of mystery to me as I haven't really taken the time to dig into how and what they do. But I am sure someone will get you on the track to getting it sorted.

The reason I stated your sensor logic as Vxx is I have not looked at the schematic yet to determine whether it is Vcc or Vss. http://encyclobeamia.solarbotics.net/articles/vxx.html

At this link you can find the factory harness diagrams for the Ranger and the Explorer.
http://search.ebscohost.com/ Username: tech password: tech

If I get the time I'll take a look at how the O2 sensor system actually signals the PCM and possibly make an educated guess but until then your best hopes lie with ADSM looking back over this thread.

 

[bort]

Thank you PanamaExpat for the access to the diagrams, Im stoked to have something to compare that Chiltons to. Now as far as the truck...

If something like a sensor has a dead short it could/would pull the entire leg of that logic circuit to ground and be in a perpetual off state. Have you checked the following: resistance readings through the individual sensors, looked for a pinched or abraded cable that could be shorting Vxx to ground

I think you are on the same thought path as I am but with the correct words to describe it. If I had a short it would pull the whole leg to ground, I would however think that I would lose the readings off of my other sensors though and that would imply that the common wire at pin91 would be the Vxx since its the only shared wire. I have checked resistance through each pin at the ECM to each sensor connector and all came up as good. The diagram unfortunately does not tell me the path of the current so if pin91 is not supposed to ground and is actually supposed to be Vxx in then theres a real problem.

or since you have stated that this is a SWAP vehicle that someone did not get one of the sensor feeds on the engine harness wired wrong?

On the O2 sensors I know that the pins go to the correct terminals on the sensor; I made it so (only because the Chiltons separates the heater and sensor wires on the diagram). As far as the other sensors TPS, IAT, etc... (that share pin91) I dont know if the pins go to the correct terminals on the sensors I have not yet accessed that kind of detail. And I dont know what the resistances should be for each sensor. I plan to investigate more today.

Quick question for you electronic knowledge, According to my Chiltons (I haven't accessed what you gave me yet) both O2 sensor21 and sensor12 (driver, behind cat) are connected to pin35 and pin91... How could the computer differentiate the signals if both in and out are common? this is what makes me question that diagram.

Again thanks for the link, hopefully be able to tell you more/good news after the next few hours of chain-smoking and banging my head on a radius arm.

 

[bort]

No good news....

the wiring harness is correct, its for a ranger; per the wiring diagram PanamaExpat gave me (thanks again).

NOTE THE CHILTONS MANUAL FOR 91-99 RANGER/EXPLORER/MOUNTAINEER HAS A BAD WIRING DIAGRAM FOR O2 SENSOR21 (sensor2 in the diagram) IT SHOULD GET VREF FROM PIN87 NOT PIN35

I've learned that the refurb computer put out 12v on pin94 which is supposed to be heater return for sensor21. So I'm thinking I got sold a bill of goods there.

Ive gone back through all connectors with component cleaner and dialectric grease. Ive can see the output voltage for all three sensors fluctuates between 0.200v and 0.800v when the sensors are plugged in and the truck is running but its definitely not enough to show the sensor.

I'm down to: I should play the lottery because I have two bad computers,and I send out one of the computers to get it checked and put tune on it anyway. Or I have 3 bad O2s.

 

[BRUTUS_T_HOG]

The 25 dollar challenge. $25 via paypal to the first person with the
correct diagnosis. If you don’t believe me then don’t help, but the
way I see it there’s nothing to lose so all help is appreciated.
Trying to find someone to actually read through what I’ve done and
give it some real thought as my head hurts from doing so, and I’m
nearly out of ideas.

The truck:
97 ford ranger ext cab 4x4, 4.0 vin x, m50d manual trans, BW1354
manual transfer case, 8.8 31 spline exploder rear with discs and
4.10s, 33x12.50s, 330000mi on the truck, 80000mi on the engine.

The problem:
-My O2 sensors all read 0.000, yes all three of them. This is causing
my fuel trims to all read -100.0. The VSS also reads 0 all the time.
-These readings have all been taken live during every possible driving
condition I can create and they have all been on three different
scanners including the stupid expensive snap-on type. I have MIL
indicating lean bank 1 and 2. Understandable considering the sensors.
-The truck runs alright, starts, runs, doesn’t die, and throttle
response isn’t bad. Definitely smells rich though.

What I’ve tested/tried:
-Checked all fuses- all good
-Cleaned MAF- no change
-Checked voltages to MAF, IAT, TPS, Temp sensor- all within range
-Tried 3 different DPFEs I had access to (correct part numbers)- no change
-Checked Voltage to DPFE- within range
-Checked voltages to O2 sensors- (key on) 12.5V in (heater), 2 grounds,
nothing in or out of 4th wire on all 3 sensors
-Replaced one O2 sensor-no change (shot in the dark)
-Borrowed a PCM with matching #s- no change
-Triple checked with multiple dealers that the PCM was correct part
number for the truck. (discovered it’s a 49 state truck)

Conclusions:
Somehow I think I’m losing VREF to the sensors and VSS. My only
remaining ideas are:
-the wiring harness is incorrect for the computer pin connector
-I have an open VREF wire for the sensors. However the VSS and O2s have
different VREF supply based on the wiring diagram.
-I managed to diagnose 3 bad DPFEs. Based on the wiring diagram I
can see how they would mess up the O2 sensors.
-I somehow opened a loop on the lower wiring harness by disconnecting the electric transfercase to put in a manual.

As stated $25 via paypal for the right diagnosis. I should have the
answers to any followup questions, if I don’t then maybe you’re on the
right path. If you come up with the answer on wred or thurs I will tell you but you may have to wait till Friday for me to get paid as this project is expensive.
Thanks, Kirk

Hmm. I like a challenge. I will have to revisit this thread after work tomorrow

 

[bort]

Ok so somebody please correct me if I'm wrong....

In the tech library theres a small writeup on O2 sensors. I was under the impression that the sensors work by reading resistance but in that writeup it says that the sensors actually create the voltage and there is no 5v in. At least this is my understanding of it. I can see this voltage off of each sensor at the computer 0.100-0.900v. This says to me that the computer is actually getting the reading. I also let the truck run all connected for an hour and got no codes. Then I started disconnecting and reconnecting the sensors one by one to listen for changes. The idle did change, started running like crap without them, so the computer seems to be using them as well, but I still have scanner readings that say 0.000 on the O2s and -100.0 on the fuel trims.

The idle however did not react at all to my removing the DPFE and EGR vacuume actuator. so I guess it was a 49 state truck.

Am I chasing unicorns, does a 97 actually send this info to the data link? If anybody has a good 97 4.0 OHV and a scanner I would greatly appreciate someone checking.

Time to start checking the data link connections closer.

Side note, I got my hands on a ECM from a 98 exploder manual 4.0 OHV. Pretty much the same wiring. Problem is it wont start the truck because I think the exploder had PATS. Anybody know the quick and dirty way too fool it?