Anybody have experience with obdii iPhone apps?

I'm hoping somebody here has experience with 1st Gen Tacoma and an OBDII scanner with an iPhone app. I'm troubleshooting a P0420 code on a 2002 3.4 taco, "catalytic converter efficiency below threshold" or something to that effect.

I have brand new cats installed, and unfortunately I also paid a shop to replace both O2 sensors (well technically 1 O2 and one AF sensor). First they said it was one sensor, I paid, then after the code returned they said it's the other. Fuck.

So, I'm now troubleshooting on my own. I bought a Foseal obdii scanner that links to my iPhone. Just plugged it in today and checked it out. The app I'm using is OBD Fusion. What I notice is the app reports "O2 sensor 1" and "O2 sensor 2".

O2 sensor 1 reports no output. Is it safe to assume that the app is referring to the AF sensor just before the cats? Anybody with experience?

 

Sensor 1 is before the cat, AKA upstream and B1S1 it is supposed to be an air fuel sensor and no output may be wromg sensor or loose/corroded wire/connection. a simple multimeter OHMS test should read .07 to .11 unless it already died. Check freeze frame data if you havent cleared the code and your scanner will do freeze frame. Live data while driving is helpful if it will do it. Also an exhast leak before S1 will throw P0420 as will a cracked exhaust manifold. A good shop will have diagnostic scanner and not just throw parts at it on your dime.

 

Thanks! My manifold and exhaust system is pretty good, just did an engine swap and replaced all the exhaust gaskets with OEM parts and torqued everything to spec. That part I did myself and did a great job.

The shop I had look at the CEL gave me good indication their tests definitively showed the downstream sensor was bad, I was so happy I just said "go ahead and replace it." Then when the CEL came back I brought it back to the shop and they then said the front sensor was bad. Again, just happy to have it fixed I said "go ahead and replace it". Shit I could have just thrown parts at it for less money. I should have just done my own troubleshooting from the start.

Thanks for the tips!

 

You are welcome. Just did an engine swap is an important detail to have left out of your original post. Any other details left out?

 

The same code was present prior to the engine swap. The old engine threw a rod. When I did the swap I had all the injectors serviced and flow tested. I cleaned the MAF.

 

I still suspect a exhaust leak upstream of B1S1. Possibly manifold or flange joint upstream. Plug the tailpipe while engine running and check for leaks. Run a tank of ethanol free 87 octane gasoline. Some cheap gas stations gas is over 10 percent ethanol Toyota says is a NO NO.

 

So the ODB scan indicated no output B1S1? Is that correct?

 

sorry about the book...

there might not be anything wrong with the app or the sensors. I will try to explain. The A/F sensor, the one in front of the cat or B1S1, immediatly reads the O2 content in the exhaust stream and the sensor adjusts the output voltage and the PCM reads this and immediatly adjusts the time that the fuel injectors stay open. The rear O2 sensor, B1S2 reads the O2 content of the exhaust as it leaves the cat. The cat is nothing more than and O2 storage device and it uses this O2 to burn and convert harmful exhaust gases ito less harmful gases and water. If the cat is doing its job there should be less O2 coming out the back of the cat than goes it the front. There is a ratio of how fast and how many times the front A/F signal switches compared to the rear O2 sensors switches and if the rear O2 sensor adjustments mimics the front O2 sensor then the cat isnt doing anything.

Other things can effect the O2 content such as false air (Vacuum leak), a flaky MAF, a small exhaust leak etc. This is where $ spent with a tech who knows and understands what is going on is worth the expense.

There is a device that Underdog Racing sells that plugs in between the rear O2 that smooths out the signal and fools the PCM into thinking that the cat is doing itys job... I have one on each of my Tacomas that are in Mexico... the low quality gas down there used to trip this code all the time, the cats are original and are marginal at best.

Now, as to your original question, you get what you pay for. I have used a couple of $20 iPhone apps.. FixXD, iirc, and the other I deleted immediatly it was so bad so I do not remember. They are good enough to just read codes and to use for diagnostics I found them to be untrustworthy.

My first and my goto app/device is BlueDriver. It does everything I want for an inital diagnostic and when I need more I will choose one of my other scan tools depending on the year/make/model of the vehicle I am tinkering on atm. I dont do professional repairs anymore, fixing cars for a living has gotten to the "it sucks" stage many years ago, nah, let me correct that, it is the customers that got to the it sucks point. One more thing about scan tools... there is no ONE scan tool that does it all. Manufacturers are continually modifying what can be scanned... some vehicles require a scan tool if you replace the battery, some require a scan tool to reset the oil change reminder light.

If you are needing the CEL to be off for smog purposes the Underdog device is illegal as it is a smog defeat device... having said that, the P0420 code does not happen immediatly, it takes a few miles of driving for it to trip. Install the device, drive her around to clear the smog monitors, I hope your iPhone app shows if it is smog ready or not, and if it is for smog purposes stop around the corner from teh smog shop and unplug it and put it in your pocket. Your 2002 should be a ODBII check only and not require a tailpipe test.

 

It doesn't use that specific term "B1S1", but it does indicate 0 output from O2 Sensor 1. I'll hopefully have more time this evening. Sensor 2 does indicate some output.

And yes, I need this thing smogged.

 

Even if the tailpipe test is not required the inspectors OBD will show a not ready or O2 pending when engine is started OBD check engine READY with O2 imitator removed. He has new cats and a/f and O2 sensors installed but wants it to be right not just pass or fail state inspection.