MAP Posted October 9, 2014 Share Posted October 9, 2014 Does anyone know what the normal output voltage is for the front oxygen sensor on our GTs? My autoxray scanner shows the output to be between 2.2V to 2.7V at idle. The downstream sensor stays at around 0.5V. I also have a GoPoint bluetooth dongle that works with an app on my IPAD.. that damn thing shows 0V for the sensor 1 output.... I've always thought oxygen sensors vary between 0.1V and 0.9V or so... i.e. less than 1V. I read that Toyotas have a different type of sensor that can have an output between 2V and 4V and that the behavior is the reverse of most oxygen sensors. A high voltage is a lean condition and low voltage is a rich condition. Does anyone have answers on this? I'm trying to troubleshoot a P0171 code, lean condition. Tough to do if I can't figure out what the correct oxygen sensor output should be. My vacuum gauge shows near 20inHg at idle so it would have to be a very tiny vacuum leak if that is the cause. I reset the code about a week ago and it hasn't come back. My scanner shows no pending code either.. Any input is appreciated. Thanks. Link to comment Share on other sites More sharing options...
Max Capacity Posted October 9, 2014 Share Posted October 9, 2014 http://people.csail.mit.edu/ilh/vacation/ should be in the service manual WHen you replace it, I 'd use a OEM front O2 sensor, my after market one lasted 2 years. 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
MAP Posted October 10, 2014 Author Share Posted October 10, 2014 I've looked through the manual but couldn't find a clear answer which is why I posted. I'm not sure that I need to replace it. The one in there is a Denso sensor that I installed 2 years ago which I believe is the OEM part. I'll keep researching this. if someone has the info, let me know. Thanks. Link to comment Share on other sites More sharing options...
apexi Posted October 10, 2014 Share Posted October 10, 2014 I don't think it's the front oxygen sensor, I would look everywhere for a vacuum leak. The FSM doesn't mention the o2 sensor being a possible culprit for p0171, and after doing a little searching here the solutions have been fixing intake leaks or finding disconnected vacuum lines. Link to comment Share on other sites More sharing options...
MAP Posted October 10, 2014 Author Share Posted October 10, 2014 The issue with that is that a disconnected vacuum line would show up on my vacuum/boost gauge. It doesn't. If it's a leak it very small and intermittent, which is the worst type of problem to track down. My line of thinking is that if the oxygen sensor was biased toward reading lean, the short term fuel trim would compensate by making the mixture rich and if high enough would set off the P0171. I've been checking the fuel trim at idle and at 2500RPM or so.. I've had cases where the trim will be low +5-6% or so at idle and then jump up to 14-18% for a while. The same is true at 2500RPM. The oxygen sensor would at the very least tell me if it is measuring lean or rich. I'll probably determine this by checking the voltage measurement when I disconnect a vacuum line(should show voltage for lean condition) and again when I spray throttle body cleaner or ether into the intake(should show voltage for a rich condition). If it doesn't change, I'm suspecting something wrong with the oxygen sensor. I think I'm going to finally replace all my vacuum lines and possibly the intake tube to the turbo to eliminate those as possibilities. Link to comment Share on other sites More sharing options...
Max Capacity Posted October 10, 2014 Share Posted October 10, 2014 Before replacing the lines, I'd might try a boost leak test. See if you can find the leak. If a hose has a small crack in it... 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
MAP Posted October 11, 2014 Author Share Posted October 11, 2014 Max, I've had the silicone vacuum lines for a while, just havent gotten around to replacing them. The engine has 120k miles on it. Many of those vacuum lines are rock hard. If one of those lines is cracked i should be able to find it in the process. Link to comment Share on other sites More sharing options...
Max Capacity Posted October 13, 2014 Share Posted October 13, 2014 I'm betting you have one thats cracked. Put normal hoses back on. 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
MAP Posted October 13, 2014 Author Share Posted October 13, 2014 Max, I phrased things a little odd... What I meant to say is that I have only installed 1 section with silicone hose at this time but was planning on replacing all the rubber hoses with the silicone stuff. Many of the rubber vacuum hoses on there now are rock hard. The silicone hose from what I can tell doesn't seem to have the same cut resistance as the rubber stuff, but it should do better with the heat. Have you had bad experiences with the silicone hose? Link to comment Share on other sites More sharing options...
MAP Posted October 28, 2014 Author Share Posted October 28, 2014 Just wanted to give an update on this. I was trying to figure out what was causing a P0171 lean code. Everyone seemed to think it was a vacuum leak which was a possibility but I couldn't find one. So I though if it isn't a vacuum leak then maybe it's running lean because my injectors are partially clogged?? I've always used fuel injector cleaner once or twice a year, honestly thinking I was doing the engine some good without ever actually noticing any difference. My local Autozone had a bottle of Techron fuel system cleaner, that treats up to 12 gallons on sale for less than half the price of the bottle that treats up to 20 gallons of gas. So I said what the hell, I bought 2 bottles that treat up to 12 gallons each and put them both in the tank at the next fill up. So I was running this at 40% higher concentration than what they sell it for. Within 1/4 tank I noticed a considerable difference in throttle response and smoothness at idle. I've refueled a couple times now and the lean code has not come back. I checked the fuel trims and they are much lower. Sometimes even going between negative and positive while before it was only staying positive and would jump up to 14-18%. Over the past year I noticed that there seemed to be slightly more lag on acceleration than the normal turbo lag. I never would have thought it was due to clogged injectors. I maintain my car pretty well. I was surprised this took care of the problem. This engine is definitely more touchy than a normally aspirated version. From now on I'm putting in a bottle of Techron with every oil change and making it a 1.5 to 2x concentration at least once a year. So for anyone with a rough idle or lean code, you might want to give this a try first. Link to comment Share on other sites More sharing options...
JmP6889928 Posted October 29, 2014 Share Posted October 29, 2014 You are correct in .1V to .9V and it should be up and down the scale when it runs. Try the Berryman B12 Chemtool injector cleaner and I think you'll notice a difference. Link to comment Share on other sites More sharing options...
fchen0000 Posted November 1, 2017 Share Posted November 1, 2017 Actually I read from Amazon that Chevron sells fuel injector cleaner and fuel system cleaner. The only difference is the concentration, the system cleaner is more concentrated. I believe I am experiencing the same problem and it's getting better with one normal treatment. I will do another one at higher concentration soon. Just wanted to give an update on this. I was trying to figure out what was causing a P0171 lean code. Everyone seemed to think it was a vacuum leak which was a possibility but I couldn't find one. So I though if it isn't a vacuum leak then maybe it's running lean because my injectors are partially clogged?? I've always used fuel injector cleaner once or twice a year, honestly thinking I was doing the engine some good without ever actually noticing any difference. My local Autozone had a bottle of Techron fuel system cleaner, that treats up to 12 gallons on sale for less than half the price of the bottle that treats up to 20 gallons of gas. So I said what the hell, I bought 2 bottles that treat up to 12 gallons each and put them both in the tank at the next fill up. So I was running this at 40% higher concentration than what they sell it for. Within 1/4 tank I noticed a considerable difference in throttle response and smoothness at idle. I've refueled a couple times now and the lean code has not come back. I checked the fuel trims and they are much lower. Sometimes even going between negative and positive while before it was only staying positive and would jump up to 14-18%. Over the past year I noticed that there seemed to be slightly more lag on acceleration than the normal turbo lag. I never would have thought it was due to clogged injectors. I maintain my car pretty well. I was surprised this took care of the problem. This engine is definitely more touchy than a normally aspirated version. From now on I'm putting in a bottle of Techron with every oil change and making it a 1.5 to 2x concentration at least once a year. So for anyone with a rough idle or lean code, you might want to give this a try first. Link to comment Share on other sites More sharing options...
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