Finally asking for help... both ho2 circuits out

[Kamel]

Alright, I have been working on this for quite some time now. Finally, I've decided to ask for help. Not like me, because I enjoy figuring things out on my own or without having to ask and bother others with my troubles. Anyway, here's what's going on.

1995 Ford Ranger XLT 2.3L 5speed

Throwing codes: p0135 & p0141 (heated o2 sensor heater circuit, both banks)

Only had it for about a year, not sure what prior owner has done to it (had codes when I got it)

I went ahead and replaced both o2 sensors, and they looked in pretty good shape -- they also broke free pretty easy, so I'm pretty sure they were new (ugh, wasted money sucks). Just to be sure that didn't fix it, I cleared my codes and they came back after a quick drive around the block.

I also checked fuse #20 in the cabin fuse box and it's fine. Also checked for voltage to both sides of the fuse with the key on, both good (I also used a test light to confirm... I once had an electrical problem that was reading good volts but not powering a test light so I always do this lol). I decided to try and test amperage draw on the fuse, and it ended up being 0 amps, so whatever it is doesn't draw much current or it's got a broke wire somewhere.

I couldn't determine any other fuses that the o2 sensors could be on, but I'm not sure if I'm looking at the right fuse. I've failed at finding a decent wiring diagram for my truck. I saw a few things on the net talking about checking a "light blue/orange cable" to the o2 sensor, but all I'm seeing is 2 white cables, a grey one, and a black one. I couldn't see the color of the wires coming from the harness of the vehicle itself all covered, but I'm going to try again soon.

Having said that, I have a couple of questions.

1) Even if it doesn't help me fix this issue, it'd be cool to find a decent wiring diagram if anyone knows where I can get one
2) Is fuse #20 (15A) in the cabin fuse box the correct fuse?
3) Should I be able to verify the o2 sensor heaters are getting power by turning the key in the on position then testing for voltage between the frame of the vehicle and each pin of the o2 sensor plug? How many of the pins are powered, just one?
4) How is the wiring routed for the o2 sensors? I see it going up and around the transmission, then I lose it

and finally...
5) Am I on the right track? Maybe you have a totally different idea, I'm open for suggestions!

Thanks a lot guys

 

[Mark_88]

I found a wiring description but not a diagram in the on-line repair manual...according to that you need to look at fuse #5 for the O2 sensors.

There may be a diagram in the manual but I didn't see one...plenty of service and removal instructions but you may need to search through it. My Haynes manual has pretty good wiring diagrams that I've used over the years so maybe you could pick up a copy for that model year. Mine goes only to 92 but I'm sure the later models would have it covered.

To access the repair manual go to this link...you can bookmark it for later if you want but if you look at the link listing at the top of this page you can see where the link is located.

http://www.therangerstation.com/forums/showthread.php?t=319

Following wires can sometimes be a tedious job but if you stick it out it's worth the effort...

 

[adsm08]

That's fuse 20 in the engine bay fuse box.

The light blue and orange wire should have key on power, but it is better to hook to the battery negative for a voltage test. Gives a more accurate reading.

 

[Kamel]

Hey guys, thanks a lot for the help. I saw that it had been a few days since the last post here and wasn't sure this was an active forum so I also posted in explorer forum. Sorry about that, didn't mean any disrespect!

Thanks for the tip on testing from the battery negative, I'd heard it before but forgot.

At any rate, I've figured out the problem for sure is the light blue/orange cable somewhere between the fuse box and where it splits off to go to the 2 o2 sensors. Neither o2 sensor is getting voltage on that, but the fuse is just fine getting plenty of juice.

I am having a lot of trouble following the wiring harness, it seems it goes up to the top/drivers side of the transmission then I lose it. Anyone know how this harness is routed so I can find where the break is at?

Thanks!