I recently changed to high flow converters and have encountered a trouble code ever since. The code is coming from the upstream sensor, showing that it is out of Performance Range. The sensor, itself, has been replaced. The converters have been inspected and the intake/exhaust have been inspected for leaks. Is it possible that the downstream (post-cat) is actually tripping the upstream sensor, if the readings don't compare well? I am at a loss at where to go from here and my technician friend is at the point of guessing what else it could be. Any help on this is appreciated. 2007 G35x with an UpRev tune.

 

no. if the downstream o2 sensor was reading out of range there is a code for that. what is the code it is throwing? i had my 04 throw o2 sensor codes because there was a leak where the headers and the block meet.

 

P2A00. Could be any number of things. I just wasn't sure if the downstream sensor sometimes compared it's readings to the upstream, like with some other makes/models.

 

be sure to check all the wiring to the o2 sensor. make sure there is no damage and the clips make a good connection.
the code says it is running on a lean condition. if there are no leaks be sure to check your fuel injector and fuel system to make sure they are working well.

any engine mods?

 

Definitely no intake leaks, as confirmed by a tuner. It's possible that there is a leak in the exhaust, either at the manifold or on the converter itself, but my off-the-clock technician is too lazy to confirm that for me . I can't have his boss talk him in to it either, since it was off hours.

I'll have to get under there, myself, to check out the harnesses. I don't think there's a fuel issue... the fuel pressure was also checked with the tune. Would an injector issue throw it's own code? Haven't done any modifications to the engine, just the exhaust.

 

The downstream O2 just makes sure the upstream is working within spec, so it's possible. You can try seeing if you can swap the rear sensors to see if the code jumps. You can also swap the upstream sensors to see if the code jumps.

If you want to find exhaust leaks you can use SeaFoam for 10 bucks. I used it to find my exhaust leak. Suck some in the brake booster and if you see smoke from anywhere except the back there is your leak.


Did you use OEM A/F sensor?
Do you have spacers on the HFC?
If manual can you do a exhaust valve relearn?

Try cleaning the MAF as well.

 

Well, I have some form of update. I was doing a monitor/sensor test with Torque Pro today and failed the test. TID: #03 CID: $02 - Low Sensor Voltage for Switch Time

I have no idea what this means or what it may be pointing to. I want to believe that this is due to a wiring/ground issue and that the sensor, itself, is fine. However, the sensor I installed is NTK (NGK) but the actual OEM is Denso... that could have something to do with it but the car was throwing this code before switching sensors. It really sucks that my tech won't take the time to inspect the wiring harnesses... have to wonder if they could be inspected on ramps...

There is also a ground strap that isn't connected on the vehicle. It goes from the exhaust manifold to the strut tower but I cannot locate a part number for it. I checked the auto parts stores around here but they only have generic ones with eyelets at each, the Infiniti/Nissan one has a bracket for the strut tower connection. No idea if has anything to do with the o2 sensor voltage

 

 

Ok so typically those braided ground straps went to exhaust components, it might have been originally landed on the headers.

The blackened end on it looks like it got into something energized, maybe on the alternator, and arced out.

I would just fold it up and cable tie it out of the way to make sure it doesn't end up on the alternator again and fry something.

Then verify your ground path from the engine all the way to the negative on the battery. Not sure about the V36 chassis but the V35 has a main bonding jumper from the right (passenger) side of the timing chain cover that goes to the chassis below the coolant reservoir.

Also make sure both ends of your negative battery cable are brushed down to clean bare metal, apply a little electrical anti-oxidation grease to all mated fittings before reinstalling.