O2 voltage just sits there and doesn't cycle at idle? With NEW o2 sensor.

[DSM-Franek]

Any reasons why my o2 voltage would just sit at .02v at idle? And not cycle up and down like it should? The o2 sensor is a BRAND NEW Denso plug and play and reads fine during logs.

Won't just sitting at .02v at idle mess with my fuel trims?

Any ideas?

Thanks!
-Frank

 

[oldman]

I'm looking at the o2v using my logger. (pocketlogger + m130)

What are your coolant temperature sensor readings?

 

[DSM-Franek]

What are your coolant temperature sensor readings?

Never above 200 even when sitting for over 20 minutes.

It's usually between 188-195.

Thanks,
-Frank

 

[oldman]

Never above 200 even when sitting for over 20 minutes.

It's usually between 188-195.

The reason I asked is because ECU will not enter close loop until reaching 165*F so a defective ECT will cause an O2 not to cycle, your ECT is functional and I'm all out of ideas, sorry.

 

[toybreaker]

Does this problem only occur at idle?

I mean if you crack the throttle a scosche does it get happy, and start cycling?

How long from a cold start in the morning does it take to get a reasonable cycle rate/reading?

Does it take a moderate acceleration event, tease: just putting a lttle heat in my o2, ossifer.. ), before it registers over ~450 millivolts?

The signal wire is intact, as witnessed by the higher readings under throttle.

That leaves the other three wires.

I keep coming back to the o2 heater system letting you down. Does the o2 just trail off at idle, or does it chop off suddenly? We may have to check the power and ground for the o2 heater circuit next.

Or, alternatively, for a break in the other wire to the o2. It's a reference ground, and I'm not sure what would happen on a dsm if this wire is broken/has high resistance, but I've seen it do some strange things on other vehicles.

Try the fuel pressure trick I posted earlier again, and let us know what happens.

Increasing your fuel pressure has to make the mix richer.

I saw you posted that you tried it, can you do it again, and pay real close attention to what it does. We can learn a lot from that test, like whether it can actually read a rich (ish) condition at idle. If it doesn't change at all, I have to wonder if your fuel pressure regulator is well with the world... (Incorrect/unchanging fuel pressure would explain lean o2 readings and positive fuel trims)...

Is your fuel pressure control solenoid still present and accounted for?

(Doesn't Sense Make

 

[spyderturbo007]

Wow, this is really weird. I'm with Bruce on this one.....Pretty much out of ideas.

The only thing I can think of is the O2 heater mentioned by toybreaker. I know that the O2 won't begin to cycle until it warms up, but I don't know if it would function properly at WOT when it's not heated up.

The other thing that I don't understand is if the heater system is dead, you should be getting a CEL for the O2 heater. Weird. I'm stumped.

An SAFC wiring problem would effect both the Lo and Hi maps, so I don't think that is the problem either. You purchased a new OEM O2 sensor, didn't you?

 

[DSM-Franek]

The other thing that I don't understand is if the heater system is dead, you should be getting a CEL for the O2 heater.

You purchased a new OEM O2 sensor, didn't you?

The only CEL I have is my PO170 (fuel trim malfunction)

I purchased 2 brand new denso plug and play o2 sensors off of www.sparkplugs.com and installed them on January 19th. (the site you refered me too )

Thanks for the help so far,
-Frank

 

[toybreaker]

The only thing I can think of is the O2 heater mentioned by toybreaker. I know that the O2 won't begin to cycle until it warms up, but I don't know if it would function properly at WOT when it's not heated up.

Yes, the exhaust heat under higher loads will bring it up to operating temps fairly quickly

The other thing that I don't understand is if the heater system is dead, you should be getting a CEL for the O2 heater. Weird. I'm stumped.

The ecu uses a quicky resistance check to verify the o2 heater circuit is intact.

I have seen a few heater circuit wires on other vehicles that were just intact enough to not flag an open circuit. The wires flex, and one by one, the individual strands that make up the conductor begin to break. This will drop the current carrying capability of the wire slowly, untill one day it will flag an o2 heater/heater circuit code. Untill then, the vehicle will see ever decreasing heater performance. This will show up as o2 range/cycling problems under low exhaust heat, (like at idle.)

I just got to the end of the troubleshooting chart on an 06 Toyota Avalon for our local Toyota dealer with this problem. Technician "A" got a little rough on the harness, and stretched/pulled the 20 awg wire apart inside the harness during an o2 change... There was just two little strands left intact...hanging on for dear life
It was really interesting to see their techs approach to this problem, the 02 bung threads were just about worn out from swapping out the o2's....

You purchased a new OEM O2 sensor, didn't you?

(^^^sorry 'bout that, I screwed up the quote thing ^^^)

It's (very remotely) possible he got a bad unit, (it's along way from Japan, and I can visualise a shipwreck, train crash, or the o2 being used for traction in deep snow by a crazed ups driver in upstate New York... WTF ) I wouldn't expect it to read full range under throttle, but again, I have yet to see all the failures possible... .

I don't do much with the 2g platform, so I don't have an applicable wiring diagram. Can one of you guys post up the 2g o2 heater/wiring diagram? I am curious about the ground point for the reference wire, and how the heater circuit is supplied with power and ground. It may be a very simple test to check the heater with a voltmeter, and the reference wire with an ohmeter, to verify the harness integrity.

It *should* be approximately the same as any four wire o2...

1 wire is the shielded signal wire from the o2 to the ecu.
(probably okay, as it seems to read ~ ok at wot)

2 wires will be for the heater.
There is some difference's here from manufacturer to manufacturer, but generally, anytime the key is on, and the engine is running, the o2 heater circuit will be powered up.

1 wire is for a reference ground.

I've never cut a four wire o2 open, but I'm thinking that the zirconia substrate that actually produces the voltage is probably referenced to ground up this wire. The old school one wire sensors used the case for a ground, but corrosion/missing ground straps/inconsistencies in the exhaust systems ground potential would occaisionally create some interesting problems, leading the manufacturers to provide a seperate ground path. (Especially on obdII vehicles that use a pre and post cat o2 to monitor catalyst efficiency.)

How does this car run under closed loop operation?

During cruise mode, the o2 should be happily cycling away, (crossing ~450 mv several times a minute, minimum) and the fuel trims shouldn't be too crazy. The ecu will constantly increase/decrease the injector pulsewidth, in order to condition the exhaust gasses for proper clean up at the catalyst. This is know as closed loop fuel control, and shows the ecu "sees" the o2, and that the o2 values are ~ballparkish~ enough for it to vary the inj. time a schosche, and "see" the results. If the trims are skewed excessively fat or lean, there may be a fuel pressure, or tuning issue. I have seen some pretty creative safc settings covering up a fuel pressure problem, or fuel pressure to boost ratio problem...

Sometimes, it's not a bad idea to check fuel pressure under operating conditions to eliminate problems with the fuel system effecting fuel trims/o2 values. Watch for the fuel pressure to rise with boost, and fall with vacum,) My quicky fuel pressure test will show the fuel pressure that your motor "sees" at "0" boost (barometric pressure 14psi (ish, absolute gauge pressure). Compare that with the pressure at idle, with the line hooked up, and you'll see that referencing the fpr to baro should add ~5 pounds of fuel pressure. (relative to what the fpr would see at idle, with the vacum line hooked up)

One thing I'd like to have you do is to watch the o2 during cold start/warm up. The numbers at start up should be lowish at light up, then climb over 450mv fairly quickly, to somewhere in the 500~800's (ish), and then coast down as the cold start enrichment/coolant temp compensation/warm up map is replaced with closed loop fuel control. We could learn a little about the heater from the time it takes to start registering a realistic reading. At start up, a correctly reading, heated o2 will read way over 450mv after ~15 to ~30 seconds of a cold start. Depending on starting coolant, and ambient air temp, it may take a few minutes to obtain full closed loop fuel control, but it should certainly have it's act together, and the o2 should be cycling by the time the cooling fans come on. If it never comes online, or it takes exhaust heat from a mild pull to wake it up, this may be as simple as a dead o2 heater, either in the o2 itself, or a problem with power or ground in the car's harness.

Good luck with this, and please keep us up to speed on what you're doing to solve this problem. It will help us to narrow down the direction to go when/if we see this problem again.

 

[Talesin]

I had a similar problem on my 1G, with a Denso O2. It'd cycle and run just fine under throttle and actual driving, but as soon as I parked and let it idle, the cycling would get erratic.. it'd get 'stuck' at the low point of each cycle, more and more frequently until it just stopped cycling.
Swapped out for a Bosch PnP replacement (Autozone special, all they had in stock), and it started cycling just fine at idle... weirdest part was, when I pulled the Denso out, it appeared to have physically melted on one side, including having bent over and crumpled a little, and was covered in tan/khaki ash. It'd been in the car for less than a week, without TOO much heavy romping. And my fuel trims are fine, albeit slightly lean from a hacked 1G MAS.

 

[DSM-Franek]

Bringing this back!

I tried a friends o2 sensor on my car and still had the same problems.. Tried mine in his car and it cycled perfect.

So it has to be the wiring. Now my question is,

Can I rewire all 4 of the wires from the sensor to the ecu?

What kind of wires would i need?

And I know what pins the signal wire (pin 76) and the one heater wire goes (pin 60) to but what about the other 2?

Thanks for the help so far!
-Frank

 

[DSM-Franek]

Bringing this back!

I tried a friends o2 sensor on my car and still had the same problems.. Tried mine in his car and it cycled perfect.

So it has to be the wiring. Now my question is,

Can I rewire all 4 of the wires from the sensor to the ecu?

What kind of wires would i need?

And I know what pins the signal wire (pin 76) and the one heater wire goes (pin 60) to but what about the other 2?

Thanks for the help so far!
-Frank

What I mean by "what kind of wires would I need?" is,

Are the shielded? Where can I buy these?

And does anyone know where the other 2 wires go to?

Thanks Alot!
-Frank

 

[DSM-Franek]

What I mean by "what kind of wires would I need?" is,

Are the shielded? Where can I buy these?

And does anyone know where the other 2 wires go to?

Thanks Alot!
-Frank

Bringing this back again ..

could a bad boost/vacuum leak cause this to my o2v?

thanks alot
Frank