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Discussion Starter · #1 · (Edited)
Hello,

I have a 2017 Trax LT that has recently started giving me some issues. It seems fine on start up and idles smoothly. After about 5-10 or so minutes of driving the engine seems to surge when I stop at an intersection or traffic light. It also threw a P0171 lean condition code and I got a service StabiliTrak warning on the dash. This only seems to happen in cold weather below about 50 F. I used my scan tool to collect some engine data at about 2500rpm. The MAF sensor shows 4.62 g/s. Is this too low? I have attached some of the data from the scan tool.

Thanks.
 

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How does it idle? Did the lean code come back? Have you tried cleaning the MAF sensor. It is normal for stabitrak to turn "OFF" with a check engine light "ON" . Last but not least check your intake clamps for a leak if you did any work under the hood lately verify your work for loose connections wires or otherwise.
 

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Discussion Starter · #3 ·
How does it idle? Did the lean code come back? Have you tried cleaning the MAF sensor. It is normal for stabitrak to turn "OFF" with a check engine light "ON" . Last but not least check your intake clamps for a leak if you did any work under the hood lately verify your work for loose connections wires or otherwise.
It seems to idle fine from cold, but once it has been driven for 5-10 minutes, it feels like the engine is surging up and down rapidly when I come to a stop, though there isn't any noticeable difference in the tachometer. The lean code went away by itself and has not come back so far although the idling problem still exists. I did check the PCV valve and hoses to see if I could find a leak, but there was nothing obvious to me. I also tightened the air filter housing hose clamp. I will try cleaning the MAF sensor.

This only seems to happen in cold weather. For example, it happens when driving to work with the outside temperature at 40F or below, but not 9 hours later driving home from work with the temperature around 60F or above.
 

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I did notice your IAT temperature reading was a bit high and found that a bit puzzling since your outside air was only 55.4°F. Maybe you just have a bad intake air sensor. But to have 2 bad IAT being bad would be almost impossible unless you have a voltage problem.
 

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The air isn't being compressed with no load and no boost so why is air temperature reading so high. Intriguing.
 

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Discussion Starter · #6 ·
I did notice your IAT temperature reading was a bit high and found that a bit puzzling since your outside air was only 55.4°F. Maybe you just have a bad intake air sensor. but to have 2 bad IAT being bad would be almost impossible unless you have a voltage problem.
So the PCM thinks the temperature is warmer than it is, possibly causing the lean condition?
 

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Did you check your battery voltage at idle. I suspect you have a bad battery. Batteries are always at their worst when colder. These vehicles need a steady voltage to be above 12 volts at all times or ECM will start to randomly throw erroneous codes and bad signals. The sensors in question need an 11V regulated. If your battery has a bad cell it will go to 10.25 volts and screw everything up.
 

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This probably happens as you come to a stop sign an your idle tries to drop but then alternator kicks out because RPMs are too slow and ECM all of a sudden has a 5 cell voltage (10.25 ) triggering a rev signal to re-engage alternator then all of a sudden voltage is back to normal triggering and idle speed signal and the vicious cycle continues.
 

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Discussion Starter · #9 ·
This probably happens as you come to a stop sign an your idle tries to drop but then alternator kicks out because RPMs are too slow and ECM all of a sudden has a 5 cell voltage (10.25 ) triggering a rev signal to re-engage alternator then all of a sudden voltage is back to normal triggering and idle speed signal and the vicious cycle continues.
Thanks for all the info! I will check the battery voltage and update.
 

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Should be 12.3 minimum after having headlights on for 2 minutes. Anything below that needs investigating.
 

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Discussion Starter · #11 ·
Should be 12.3 minimum after having headlights on for 2 minutes. Anything below that needs investigating.
So, according to the scan tool, the battery voltage is 13.8v while idling with the headlights on and 12.5v with the engine off. The ambient temperature is 60F though, maybe I should test it again when its colder?
 

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With engine "OFF" turn lights "ON" for 2 minutes then "OFF" and measure battery.
 

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Discussion Starter · #13 ·
With engine "OFF" turn lights "ON" for 2 minutes then "OFF" and measure battery.
With the engine off, lights on - 12.2v after 2 minutes, sometimes dipping down to 11.9v.
Turning the lights off resulted in 12.2v steady.

I also started it up after this and the internal lights were flickering noticeably, if that means anything.
 

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Keep an eye on it, that seems okay but I still think your battery somehow is the culprit. You don't happen to have an other vehicle that you could swap the battery to try?
 

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Discussion Starter · #15 ·
Thanks for your help. I don't have another vehicle, but I did get the tires replaced just before this started and the tire place tried to sell me a number of things including a new battery. It's a couple of years old so I may just replace it and see if it solves the issue.
 

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The WalMart brand made by Johnson is a good battery. Don't get anything made in Mexico or China.
 

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Discussion Starter · #17 ·
The WalMart brand made by Johnson is a good battery. Don't get anything made in Mexico or China.
I replaced the battery, and this seems to have increased power while driving, especially on hills, but unfortunately it hasn't solved the original problem. It is colder weather today and the car again idled fine from cold, but was surging and rough idling when I stopped at lights etc. It also threw the P0171 code again. From the freeze frame data (attached), the IAT values look better, but the fuel trims are off. It looks like I should be checking again for a vacuum leak?
P0171 Freeze Frame.JPG
 

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Hello,

I have a 2017 Trax LT that has recently started giving me some issues. It seems fine on start up and idles smoothly. After about 5-10 or so minutes of driving the engine seems to surge when I stop at an intersection or traffic light. It also threw a P0171 lean condition code and I got a service StabiliTrak warning on the dash. This only seems to happen in cold weather below about 50 F. I used my scan tool to collect some engine data at about 2500rpm. The MAF sensor shows 4.62 g/s. Is this too low? I have attached some of the data from the scan tool.

Thanks.
I have a 2017 trax and it threw the same code at me just yesterday. I still owe money on the darn thing also. I'm going to test out the if it has a leak around the MAF later today. My engine seems to be running just fine.
 

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Discussion Starter · #19 ·
I have a 2017 trax and it threw the same code at me just yesterday. I still owe money on the darn thing also. I'm going to test out the if it has a leak around the MAF later today. My engine seems to be running just fine.
I have narrowed the problem down by unplugging the Purge Valve's electrical connector. After this the car drives perfect and fuel trims are normal. I don't think the Purge Valve is stuck open because there is no vacuum from it. Could it be something further down the line?
 

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Could be rodents chewing on wires. Did you apply 12 volt to the purge valve to see if it worked. And maybe I did see negative pressure from the fuel sensor I'll check again. -3.44 I think this number is suppose to be positive when engine running..
 
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