I’m new to the camry world. I hooked my scanner up to the obd2 port and got a little surprise. The scanner is only showing O2 volts for sensor 2 which I assume is downstream from the cat. It only displays some long term (?) O2 volts for sensor 1. Neither of these sensors display the usual continuous switching waveforms during closed loop operation that I’m used to seeing on other cars however the system otherwise seems to be happy with no fault codes or CEL. Engine runs fine. Also the LTFT goes pretty high at about +10% during idle condition but settles at lower values of less than 5% with even a small amount of throttle or load. Again this is not the kind of operation I’m used to thinking is typical.
Is something wrong here or is the 2014 Camry fuel injection different than American cars a few years older? What should I expect the O2 volts to look like during closed loop operation on this Camry? All help with be appreciated.
Confused for now.

 

Doubt something is wrong or the check light would be on.

The fuel system is not always in closed loop such as starting, cold engine, hard acceleration, fuel cut off and wide open throttle. If not in closed loop the A/F sensor signal will not be used.

What does the waveform look like, it is a sine wave?

 

The commanded and measured air fuel sensor signals track well provided its in closed loop. i expect this. The only available O2 sensors are wide range voltage for sensor 1 and sensor voltage for sensor 2. I dont know what wide range voltage is supposed to look like. During closed loop its constant at 3.2 volts. Sensor 2 volts switches from the usual range of a few tenths to 9 tenths of a volt. This only swithces every 10 seconds or even longer again during closed loop operation. i'm not really sure what to expect here since my understanding is that sensor 2 is only used to monitor the cat and for some reason i don't have access sensor 1 volts, only its wide range volts whatever that is. Normally sensor 1 volts would switch frequently during closed loop but i can only read what is called sensor 1 wide range volts.
Any insight as to what these volts are supposed to look like or why i can't pull sensor 1 volts from the computer??

 

The first sensor is an A/F, the second is an 02.

The O2 will have a lower voltage output and yours is right in the range.

Normal first sensor output alternates around 3.2v. So, this is correct.

 

Thanks toyomoho. I'm not familiar with A/F sensors. All my prior endeavors were with O2 sensors only and these switched about once per second or so. Clearly the A/F sensor doesn't look like the classical O2 sensor. I'll google it to see what i can learn. In the meantime:
1) Why is my scanner identifying sensor 1 as an oxygen sensor with a wide range voltage? is this simply another designator for an A/F sensor?
2) Is the sensor 2, the actual O2 sensor, simply used to check if the cat is working and not actually used by the fuel injection?
Thanks for your help!

 

1) Yes, an A/F sensor is an O2 sensor having a wide range voltage. Also called a wide band or wide range air fuel (WRAF).

Unlike an O2 sensor, an A/F sensor has a heating element to bring its sensing element up to operating temp quickly. O2 sensor only work well when hot, about 600F.

The O2 is a rich/lean sensor which switches rapidly and sends out a voltage signal to ECU.

The A/F sensor system has a reference voltage applied to the sensor from the ECU (3.3v for Toyota). The sensor voltage gradually changes with A/F ratio which is compared to the ref voltage, which then generates a varying current which is what is actually used by the ECU.

2) Yes, Sensor 2 is there to check for cat performance and not fuel injection. Would presume this sensor need not be as complex as the criteria for a failed cat is either good (signal from O2 sensor deemed within a range) or bad.

 

Thanks very much toyomoho for the very thorough explanation. This is what I was looking for!
As long as we're on the subject of A/F sensors here's two more questions:
1) Are the A/F sensors the same in all states for a given car or does CA have a different version?
2) I always assumed the only pollution equipment on a given car that is different in CA is the Cat. Is this correct?
Thanks again!

 

1) Toyota switched from the 02 to A/F for all emissions standards some time ago. Prior to this CA cars had the A/F sensor. Prior to A/F sensors coming into use, Toyota used 02 sensors.

2) When CA mandated their own emissions standards Toyota built cars to federal or CA standards. The CA car could have had a second cat plus other changes including to the engine.

There was a label on the car stating meeting FED, CALIF standards or something to this effect.

Thought Toyota now builds all cars to CA standards.

CA has their own emissions control board (CARB) which must certify the emissions parts. Thus aftermarket cats must meet CARB standards. This is why when looking for after market cats, many have verbiage stating not legal for use in CA. This is because they are not certified by CARB which costs $$. It is possible they still could met CA emissions standards if the manufacturer wanted to comply with CARB certification requirements.

Since fed law mandates the cat be warranted for 8 years or 80K miles, there may be no sense in aftermarket manufacturers certifying their product at this time for later model cars still under fed warranty.

 

Interesting. When I hooked up my scanner to my 2014 Camry (a Texas car) it said something like:
“the ECU complies with OBD-II as defined by the CARB.”
1) I found that to be mystifying since it’s not a CA car and I doubt it’s been tampered with. Is this because as you mentioned, Toyota now builds all its US cars to CA standards or is it because the OBD-II specification is a CARB specification that has been adopted by the EPA (or the FEDS) or do you think there is a different explanation?
2) I have never heard that CARB has specs for any emissions part other than Cats, at least for recent cars. Do you know differently?
Thanks again for your help!

 

1) California required on-board diagnostics in cars around 1991. Then in 1996 required improved diagnostics. EPA required standardized diagnostics for cars in 1996. The purpose is to diagnose and maintain emissions standards.

Your car also meets CA emissions requirements. Assume given California being a large market for cars, plus other states having their own stricter rules. Toyota decided to build all cars sold in the US after a certain date to meet CA requirements. Canada and other countries have their own requirements which can be lower and car makers builds cars to meet these requirements.

As CA goes, the Feds seem to go. Thus the saying CA leads the way in emissions regulations.

2) In CA, it is OK to replace a factory cat or other part related to emissions (exhaust) with another factory cat or part. The car marker has been granted an executive order that links everything together in the cars design to meet and maintain CA emissions requirements over the life of the car.

An after market part marker wanting to sell parts related to generating or controlling emissions would need to show their part maintained this linkage. They would then be granted an executive order certification the part meets or beats what would be assumed the original part specs.

If your car is in Texas, you need to maintain Texas State emissions rules. These rules may allow you to replace say a cat with a non CA certified cat or just state nothing about replacement parts. The state sets their emission rules but still must comply with federal rules.

California states the car manufacturer specifies what replacement camshafts, carbs, cats, ECU, electronic ignition systems and more can be used. It is illegal to replace a camshaft unless it has the same specs (profile) as manufacturer specs. If not the after market manufacturer needs to obtain a executive order certification. It is illegal to swap engine parts such as heads from another engine model unless the replacement heat meets the same specs as the original. Or the head has a certification.

This limits performance increases by swapping parts between engine models as is sometimes done.

California has verbiage of what can and can not be done in great detail and lists of what after market manufacturer parts are certified. Some parts such as ign coils and wires can be swapped if the part meets OEM specs. Perhaps this is why vendors state a part meets OEM specs.