Warrior62

First off I want to say thanks for your time and attention regarding these matters, you all have never let me down before!

Well, here are the codes Im throwing:

P0720- Output speed sensor circuit malfunction
P1151- Manuf. Cont. Fuel/Air Metering
P0174- System Too lean (bank 2) (tears)

So..heres how I messed everything up. Saturday I decided to wire up my narrowband A/F gauge (Lightshow I know, but got it for next to nothing) thinking it would be a piece of cake, using this write-up: http://www.stangnet.com/mustang-foru...lete-n00b.html. I spliced into wire 87, for the passenger front o2 sensor (red, black stripe) going into the pcm, however i didnt do it the same way as described in the write up..I instead (regretfully) cut this wire in half because it was so short and bridged the two with another wire, something of greater gauge. I then proceeded to wire in the A/F gauge wire where the factory wire and bridge wire meet. This may be a ****ty conection and may very well be the answer to trouble code P0174, but I would want to get other opinions first. As for the other trouble codes, they are causing my speedo to cut out and stop working, and my car is not running normally, every once in a while I'll get a little hesitation. Im scared to drive her but must, so I am being very conservative.. I am wondering if maybe I nicked another wire or two when removing the electrical tape, that being a possibility. I have the wire colors for these components and will check them for damage in a few hours once i get out of class. I will also post up pics of my "splice". For now, any suggestions on how I might want to do to resolve these issues would be greatly appreciated!!

Thanks again!

DJ

school boy

its a long shot, but the o2 sensor is measured by voltage. with the gauge drawing in voltage may be throwing the a/f ratio off to the ecm

Warrior62

That would make sense though, I really believe the o2 sensor readings are being distorted before they get to the pcm.. Thank you for the input.

Any other ideas guys?

update: my odometer is sometimes going to a blank screen like so [------------]

ill post up a pic of my wiring

cliffyk

In the first there was no need to use a larger gauge wire for the jumper, a chain (be it a real chain or an electrical circuit) is only as strong as it's weakest link--did you solder the wires?

P0720 is as you have described, click here for more:

The OSS signal is a dark green/white wire at pin 84 of the PCM, it's return circuit (also used by other sensors) is a gray/red wire at position 91 of the PCM connector.



P1151 means the bank 2 (drivers side) front O2 sensor, the one you tried to tap in to, is not switching and is indicating a lean mix--click here for more.

It likely means the signal wire (pin 87) is open (or shorted to ground).

P0174 is again as you have listed, no doubt a result of the above issue.

So. check your connections (they should be soldered); and check out the dark green/white wire at pin 84, and the gray/red wire at pin 91.

Warrior62

Wow thank you so much for the detailed response, it really helps matters!!!

No cliff I did not solder the wires, work space is kinda tight but I will do my best to reconfigure my wiring and solder the connections.

So does open (or shorted to ground) mean that the signal wire is grounded?

Im a mechanical type of guy, not electricial so this was kinda a first for me..learnin the hard way

I will check the car now and get up a few pics, keep you updated.

cliffyk

"Closed" and "open" with regard to electrical connections (switches, relay contacts, etc.) mean connected and not connected; "grounded" means connected to ground--good for a ground wire, not good for a power supply (+12V) or active signal wire.

If the O2 sensor connection is open (not connected) or grounded (inadvertently connected to ground) then the PCM will see a constant low voltage signal--coming from a narrow band O2 sensor a low signal indicates a lean air/fuel mixture.

Also, in closed loop operation the O2 sensor signal oscillates ("switches") between 0.3V and 0.8V or so, at a rate of 1/2 to 5 times a second, as the PCM continually changes the amount of fuel injected to maintain an average AFR or 14.7:1--obviously if the signal wire is open or grounded the signal will not oscillate. The PCM monitors this and knows something is wrong when the signal does not change as it should...

Warrior62

That makes perfect sense to me, other than the fact that I am getting a signal to my A/f gauge, it does seem to oscillate and bounce back and forth as its intended..maybe I am mistaken but wouldnt that lead you to believe the pcm is getting the signal also?

I am not really able to take any pics tonight bc my mom is asleep and idk where the camera is, however I really havent been able to pin point any damage to the wires mentioned previously. I really want my car back to normal..this sucks bc i am getting alot of welding done the 1st and gears, axles, lsd so i must get this sorted out asap...

I meant to inquire, could the larger gauge wire be a part of the problem?

cliffyk

Nope--the O2 sensor is an active signal source; I.e. it generates a voltage and is not a passive device that modifies a signal from the PCM. It may be that the connection between the wire from the sensor and the PCM is bad....

Only if poorly connected, just the fact that is is larger is irrelevant at the voltage (0.0 to 1.0V), amperage (well under 0.001A) , and frequency (0.5 to 5Hz) of the O2 sensor signal.

Warrior62

Ok well I should now be celebrating, but instead im more freakin than before...I redid everything again, this taime just disconnecting the a/f gauge and making sure the 104 oin connector was really tightly bolted to the pcm. Again, no damage appears on any of the wires.. So I started her up and it looked as if the codes were gone! I have yet to drive her and check the speedo, but after connecting and disconnecting the battery to work on her and starting her back up it did move as it does after the battery is reconnected. However (god this hurts to type) I hope I did no damage driving the car around with these troubles...after starting and going to the engine bay, hood up, I heard a intermittent sound, something around the lines of a finger nail scratching plastic..I also noticed my serpentine belt is off a notch. while i hope this is the cause of such sound I honest dont believe it is and have no idea what this could be..please pray for my car tonight!! Any ideas what this may be? I may not even want to hear the answer..

Warrior62

OK so i wish i had a better way to describe the sound, but i am hoping it isnt too bad of news...tomorrow i will fix belt and hopefully it goes away, if not ill go to friends and hopefully we can pin point it.. I did take the car around the block and the speedo works, SES lights gone! thanks again guys. anywhoo, do you think i could have caused damage when driving her around? I kept her under 2,000 rpms but still..should i be worrying?