thook

Hello folks,

My '86 runner is throwing a code 5 intermittently. That's the "O2 sens. signal" or "sensor heater signal". Are these O2 sensors heated? Also, it says "signal". I assume this may not necessarily mean the O2 sensor itself is bad, just the signal is malfunctioning? I'm at a loss digging through the 1k's of posts on O2 sensors. I have no more time today to dig further, but I'd like to clear this issue up so I can get what I need today. (I don't get to town again until this weekend.) Could someone help me a little here, please? I'd also searched on "code 5's", turned up nothing on that. It's all code 21's or 25's.

Admittedly, I bought a Bosch (non-heated) because it's twice as much for a Denso, and I'm a little short on the funding. If I really NEED the Denso, I can manage. It will just be a stretch.

thook

Okay, I'm running some tests. Water temp sensor, cold start injector, and vacuum leaks. Any more input, if I haven't covered my bases here, would be appreciated.

BTW, O2 sensor...not heated...only one wire.

thook

Nobody?

JEBSR5

I was going to say if it is heated, there is a ohm test, but you are saying it is not?

Mine had different code but same description and tested it and ohm's fell way off what it was supposed to be for heater circuit. Replaced with Denso, cured code and raised gas milage by 6 mpg's.

If it's signal, then ECM not receiving it, erroneous data, still could be sensor. FSM show any test for your O2? Wires not burnt, laying on exhaust?

thook

Thanks for posting. I should have mentioned I have a 22re in the '86, I suppose.

No, according to the tech at the dealer, because it's "one wire" means it's not heated. "Two" would mean it was. I was in hurry and took my chances calling a tech(they aren't always available or reliable) and the guy was real, real helpful. He also sounded like he really knew what he was talking about.

I've read about the ohm test (and the volt test) in the FSM, but I didn't realized it for the heated type sensors. Are you saying it is? Is the volt test also?

I replaced the sensor already (with the Bosch), but the CEL came back on. The Bosch should work for all practical purposes. I use one on the '92 rnr and it's been fine. I would have gone with a Denso on the '86 as I did last time, but need some money for an alignment and other parts for the '92. Now, I may need more for other part/s since CEL is still on with the new sensor. Ungh!!

4runnerx3

My 88 has 4 wires and the 86 has 2. Did you try pulling the stop fuse to clear the memory?

thook

Stop fuse? As in EFI fuse?

Your '86 has two? 22RE? No turbo?

JEBSR5

The FSM is pretty much dead on, but haven't seen FSM for a one wire, so not sure if your FSM shows a test or not, but seems sensor itself is not the problem.

Since replacing the sensor didn't cure the problem, then signal must not be reaching ECM. I would start tracing wires for breaks, frays, etc. Sounds like a hard failure or light would have went off after replacing sensor, but did you remove fuse to ECM or remove battery cable for a 5 minute period to clear codes just in case?

Only thing I've heard bad about Bosch is sensor tip is not as long, so may not be giving proper readings. Don't know if it's true or not, but does make sense in a way.

pruney81

So, if I read your previous post correctly you replaced your O2 sensor and gained 6 mpg? I'll be replacing mine in my 3.0 in a few days so i hope I can get 6, I'd settle for 2 though.

JEBSR5

That is correct. Ran fine even when CEL came on indicating bad heater circuit. Went from 14 mpg to 20 mpg. Also don't have any ping. That's mixed city and highway with 50/50 city/highway miles. Don't know what straight highway is yet although it's been 6 months since I did this.

thook

The battery.

I'd not heard that about the Bosch. Hmmm....

I'll check out whatnot as per suggestion. Thanks!

JEBSR5

Pulling ECM fuse is better, only resets ECM so you don't screw up the radio. That part doesn't matter to me, so I just disconnect battery.

thook

Me neither...radio's not working at the moment anyway. Come to think of it, I rarely used the radio. Just the CD player.

Anyway, now I just have to locate the fuse. The FSM shows a different diagram on the fuse box than what mine looks like. I know, atleast, it's a 15amp. That narrows it down a bit.

thook

Not a resurrection, just an update for archives.....

Turns out it was the AFM causing the fuel ratio to be thrown off and tripping the O2 sensor. Just so anyone ever searching for code 5 issues has something to refer to.

abecedarian

/me taps thook's shoulder.....

How'd you figure that out and elliminate the O2 sensor?

874runnersr5

hmm i should test my afm, i also had code 5 and just went out and bough a bosch o2 and it seems to run way better and use less gas.

thook

Well, first I thought the NGK sensor was probably just old and bad. I was having blow by and figured it killed the sensor. Put a brand new Bosch in....code came back. Figured maybe it the wire. Tested that...nope. Adjusted valves, new coolant temps sensor, cleaned this and that, wound up having to rebuild the motor, so that eliminated blow by as a possibility...you know, gumming things up in the intake. But, after everything code still came back.

Then, when I was over at Kyle's (My99) tooling around on his rig, I got the bright idea to put his new AFM on mine. All the symptoms went away. So, tested his AFM and then mine. (Bear in mind, I'd tested mine already several times and passed). Then, I got the bright idea (because we'd been messing around with his TPS) to run a sweep test on both his and my AFM's. His was a steady constant flow in resistance like I described in another thread....."AFM testing". Mine wasn't. It had dropouts. Still not sure because I couldn't confirm what I'd found with anyone, I went and bought a new unit like his. Put it on and to this day the check engine light has not come on once and the symptoms have not reappeared. Plus, my gas mileage and exhaust odor improved. It was running to rich.......and, sometimes too lean. Occasional pinging. And, since I hung onto the original NGK sensor....just in case.....I put it back in post new AFM. Still no CEL.

So, it was never the O2 circuit or anything else because the CEL always returned. Long drawn out process for over a year.

Last week I ran this whole story by a nearby mechanic who would know if ANYONE would. He confirmed my findings about the dropouts in the AFM. It's all pretty logical, though, if you ask me.

The ECU relies on specific volt/resistance information. It makes no sense in the world anyone would make a unit with a different circuit that did not function in the same way a factory unit would (as was suggested by someone in "AFM testing" thread). It just wouldn't work. The ECU would pick up on the volt input and even though it's not detecting an error, the info is still blurbed in spots throwing the fuel mix off in those points. If it's going up from 100-200-300-400 (in ohms) the ECU reads this as the vein flapper opening. If it then suddenly drops from 400 down to 200, the ECU thinks the vein flapper has just closed slightly again. You see? It's just jumping around, but doesn't necessarily equate to an error with the AFM to the ECU. The O2 sensor picks up on it, though. Vein flapper is physically still open, but the ECU is not adding the right amount of fuel to the actual air.

Hope this makes sense. Not sure how well I e'splain.

thook

A code 5 can encompass a number of errors....atleast, on the older models. So, it may have been your O2 sensor. However, even when I first replaced mine throughout everything, it did intially run better. Or seemed to, anyway. But, I guess a brand new sensor will work better than one several years old. Maybe?

thook

Oh....and the deal with Bosch. It's not that the sensor itself isn't good, it's not that the probe is not long enough, it's that there is a threaded portion that the mounting flange screws onto. That threaded portion prevents it from seating fully into the manifold port so that flange itself bends over and doesn't seal as well as a factory unit wherein there is no threaded portion. Engh....maybe you'd just have to see a Bosch compared to a Denso or NGK to understand.

874runnersr5

hmmmm crazy.

il test my afm, but im also getting code 11 i think, tps. I havent got aroudn to adjust it or swap it our for the one i got.