Oxygen sensor? No, it's the battery!!!

[hoiskii]

Hi,
I think that my story might be useful for someone with the O2 sensor problems. Sorry if this is what's already well documented and known, but it was not in any of the repair manuals I saw.

a few weeks ago I've got a bunch of the O2 sensor error codes. And I was getting them every next day after I clear the codes. So? I was about to get a new sensor (it's ~$150 for my car) though I was a bit disappointed since I've replaced the sensor only about 45K miles ago.
....
Another thing that was weird were erratic starts.
....
One day, I left an inside light turned on through for ca. 8 hours and in the morning I could not start the car. "F^^^ ", I said. Then I jump started the car and get to the nearest "Autozone-like" store and got a new battery.
And ... surprisingly, NO O2 error codes anymore!

I have a few guesses, but I truly have no clue of what might be a relationship between a battery and an O2 sensor?

[marc780]

I have a few guesses: Maybe your battery clamps loose before you changed the battery causing intermittent voltage to computer, (causing it to think something was wrong when it wasnt); maybe your ignition switch is worn and weak battery only passed intermittent voltage to computer because of this; maybe the worn battery caused the computer to reset its memory a few times when you shut off the car and then restarted and this caused the computer to throw the codes.

I dont know and i could be full of sh%t about this, any experts have the real answer?

[ghettosled]

how long has it been since you replaced the battery? im wondering if the ECU being reset has anything to do with this.

[bigbird]

when u reset teh ecu it does take some time for the computer to redisplay codes. i reset mine with o2 codes and then a week later they came back. the ecu has to cycle through tests several times to be sure that the signal its getting from the sensor is not just a one time thing.

[hoiskii]

Originally Posted by ghettosled

how long has it been since you replaced the battery? im wondering if the ECU being reset has anything to do with this.

About 2 weeks. Before that, the codes were coming every day or two. In fact, all have been reset with the old battery, I can remember that a few times my radio settings went to default in mornings.

But still, I remember once the light came on when I was driving for a while and when I looked at the freeze-frame it was "too low coolant temperature for A/F sensor closed loop operation". This code can ONLY come on when the car is working (and moving) for a while. And this is where I am getting completely confused of how this code could be due to the battery???


But it was the battery causing the problems! After I've changed it, I drove well over 700 miles with no problems, codes, etc.

... who knows what will come up next...

[bigbird]

what were the o2 codes u were pulling at first

[hoiskii]

Originally Posted by bigbird

what were the o2 codes u were pulling at first

P0125 Insufficient Coolant Temperature for Closed Loop Fuel Control
P1135 Air/Fuel Sensor Heater Circuit Response. (Bank 1 Sensor 1)

I don't remember now, but there also was one of these codes:
P1130 Air/Fuel Sensor Circuit Range/Performance. (Bank 1 Sensor 1)
P1133 Air/Fuel Sensor Circuit Response. (Bank 1 Sensor 1)

[bigbird]

Originally Posted by hoiskii

P0125 Insufficient Coolant Temperature for Closed Loop Fuel Control
P1135 Air/Fuel Sensor Heater Circuit Response. (Bank 1 Sensor 1)

I don't remember now, but there also was one of these codes:
P1130 Air/Fuel Sensor Circuit Range/Performance. (Bank 1 Sensor 1)
P1133 Air/Fuel Sensor Circuit Response. (Bank 1 Sensor 1)

thats weird, thoes are the same codes im pulling, i did need a new battery

[jmborchers]

This happens because of the way the computer circuit board works. When you go to start your car with an old battery the voltage at the battery may drop to 6V. At this voltage the computer can't detect certain sensors properly. If you go to start the car again a little while later without a full trip COLD-HOT-COLD in between the computer will throw the code. Some codes don't need a 2 trip fault to trigger.

The specification for software should have ruled out any codes within one minute of startup to prevent these kinds of problems. They didn't, so this is why they show up.

The dealer guide is also flawed here as they don't have you look at the battery voltage during the car start up. They have you look before or after the car is running. In either of these cases, the battery voltage is likely good otherwise the car won't start.

This code trigger is a good way albeit unfortunate way to find out a battery is going bad on the vehicle.

[SaganGathering]

Originally Posted by bigbird

when u reset teh ecu it does take some time for the computer to redisplay codes. i reset mine with o2 codes and then a week later they came back. the ecu has to cycle through tests several times to be sure that the signal its getting from the sensor is not just a one time thing.

I don't know about that. I have a 2001 Camry with a check engine light throwing a P1135 code. I used one of the OBD II readers to clear my P1135 error code. I drove only about 3 car lengths before the check engine light came back on.

Somebody want to explain why that error code came back so darn fast? I expected it to take at least a few miles before it was even possible. Especially since it's supposed to take about 2 minutes for the heating element in the A/F sensor to get hot enough to even be of any use to the PCM/ECU.

[jmborchers]

I believe it's because the P1135 does not require 2 trip fault logic to appear.

[SaganGathering]

Originally Posted by jmborchers

I believe it's because the P1135 does not require 2 trip fault logic to appear.

Huh?


Put it another way, while i'm waiting for pinout info on the A/F sensor connector (to do the heater resistance test) what other things are definitely known to can cause a 2001 Camry (4cyl 5S-FE) to have a p1135 error? These are the various other causes bandied about:

Loose air intake hose?
Fuel pressure issues (maybe a dirty gas filter)?
Bad Manifold Absolute Pressure (MAP)
Coolant Temperature Sensor?
Poor connection at Air Filter sensor?
Check circuit-fuse?

Thanks!

PS According to the haynes repair manual the correct A/F sensor heating circuit resistance should be betwnee 0.8 and 1.4 ohms. That seems both low and a very narrow range to me. Where can i get confirmation on that?