O2 Sensor resistance

1.8-liter VVTL-i (2ZZ-GE) and VVT-i (1ZZ-FE) engine, transmission, exhaust, intake, and performance tuning discussions
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2006
Posts: 43
Joined: Mon Jul 23, 2018 9:01 am

O2 Sensor resistance

Post by 2006 »

Among the 4 codes I have...0031 is one of them. I may have read that it is possible to have this code come in when the intake gasket is leaking? I know I read on post in there that it is an open circuit on the heater. I also have a 0171 code.

Anyway, I changed the intake manifold gasket since the car does have 349,000 km (216,000 miles) on it and it's a cheap and easy thing to do....Fel-Pro blue, not Toyota. I thought I would check the resistance of the O2 sensor.....which indicated 1.7 ohms. I took the reading with the sensor installed (only unplugged it and took the reading). The reading is not within 5-14 ohms which I saw stated in a post here.

I figured that a heater failure or open circuit would indicate an infinite resistance....and that my 1.7 ohms obtained would not bring in code 0031.

Unfortunately the car is not plated so I cannot just clear the codes and drive it for a while to see if the code(s) return.

Do you think my PO 0031/0171 issues should be resolved?

Thank you in advance.
Paul
jolt
Posts: 945
Joined: Sun Mar 02, 2014 2:07 am
Location: Twin Cities, Minnesota

Re: O2 Sensor resistance

Post by jolt »

Check all the information here about your codes:

https://www.engine-codes.com/p0031_toyota.html

https://www.engine-codes.com/p0171_toyota.html
Do you think my PO 0031/0171 issues should be resolved?
If you look in the upper right hand corner of those pages, it gives you "Repair Importance Level" for the code. Scroll down the page, read the information and watch the videos.

Some more info: The ECM uses a fixed range of values for the heater. If it goes out of range the ECM will trip the code. Using Ohms Law and some of the information you provided here, you can figure the amp draw for the heater. At ~13 volts and said you measured 1.7 ohms, that makes for an amp draw of ~7.7 amps. A value of 14 ohms would give you about 1 amp and a value of 5 ohms would give you about 2.6 amps. From what you said above, using 5 to 14 ohms as the normal values that would put the normal amp draw for the heater at 1 to 2.6 amps and you are pulling some where around 7.5 or more. You are close to a short, just the opposite of an open circuit that you were reading about. This value is well out of range of normal for the ECM if you consider using your values of 5 to 14 ohms. A heater needs resistance in the circuit to generate heat. If the resistance is to low, little heat will be made and a lot of current will be used.

All factory testing in this system for these codes are voltage and amp measurements that are seen at the ECM. A "scanner" is required to check these values that the ECM see from the oxygen sensors. A "code reader" will NOT tell anything useful to further diagnose the problem to resolve the issue you are seeing. You should have two sensors but I am not sure what year you are working on here.
2006
Posts: 43
Joined: Mon Jul 23, 2018 9:01 am

Re: O2 Sensor resistance

Post by 2006 »

Thanks for the quick response jolt. It is an 06 Vibe I am dealing with by the way, as well as the upstream sensor...should have mentioned that in my post.

I checked another site.....toyotanation, and it mentions specifications of 1.8 to 3.4 ohms resistance for the upstream O2 sensor (03 to 08 Corrola, Matrix, Vibe). 1.7 is still out of that range.

I cleared my codes after replacing the intake manifold gasket as mentioned. I had the car running for a good 30 minutes or so and drove it around the block a couple of times, as well as to the shop that will be doing my safety check. The check engine light didn't come it....at least yet.

The evap codes I had didn't come back either (replaced the gas cap)....but that's another story.
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