[JRMF]

2012 terrain 2.4L AWD
I keep getting the p0191 code after the vehicle has warmed up and I come to a stop in gear, then limp mode is activated.
What should the low and high fuel pressure numbers read on my scanner?
Here is the list of EVERYTHING I've done so far
New head gasket, New timing chain kit with sprockets, new VVT solenoids, water pump, cam sensor (exhaust), NEW throttle body (relearned), new high pressure fuel pump, new fuel rail pressure sensor.
I guess maybe the next thing to do is get my fuel pressure numbers then maybe drop the tank and install new fuel tank pump?? I'm at a loss, everything I've replaced is because it's either thrown a code or it was recomended by other posts I have been reading. All of the things I've replaced has fixed what was wrong (at that time) all except the fuel pressure sensor on the rail, and the throttle body. Any help is greatly appreciated at this time. Thanks

 

[JRMF]

Well, Fuel pressure numbers are all over the map. while running the regular pump is pushing 31-60psi.. while the high pressure reading is around 600psi Idling. I don't like the the low side fluctuating so much so fast, ordered a new pump for the tank, we will see how it goes.

 

[stopwatch]

Have you tried taking some freezeframe data of the fuel pressure ( from the tank pump ) and the fuel rail pressure showing whats happening just before the code sets? In my shop manual ( for the 2017 nox ) it clearly states that the tank fuel pump module or the fuel pump control module could set a P0191. I'm not saying this is your problem, but you might be going in the right direction.

 

[stopwatch]

Also have you checked the fuel pressure using a gauge at the engine comparing that reading to what the scan tool is showing?

 

[JRMF]

is there just one module?? I hate to admit it but there is a mechanic fella on one of the social media things, and he did mention the same code I got and he replaced the module, looked like the weather really got the best of this thing. I really don't want to drop the tank. I just learned about the live data function on my reader(s) last night. When I checked it earlier today I tried 2 different scanners with same results. but I can throw an analog gauge on and see what that says. I'll keep you posted. thanks for the reply

 

[stopwatch]

JRMF, yes there is a separate fuel pump control module and a fuel pump. ( which is sometimes referred to as fuel pump module )
So I went for a drive this morning and took some realtime readings of the fuel pressure ( from the in tank pump ) and readings of the fuel rail pressure. Both reading were not steady - they jumped arround a alot.
Now my Nox is a 2017 with a 2.4L and is running great, no codes, no troubles, it is not a 2012 but the readings should be similar. I used Torque Pro to get these reading, they were taken on a 45F day, engine at operating temperature, running regular gas which might be E10.

1) The fuel pressure was between 37 and 47 psi when moving, it did increase to 55-60 psi when not moving at idle and returned to 37-47 psi range once I started moving again. The pressure also increased to 65 - 72 on a good WOT pull.
Cold start key On engine not running gave 60-64 psi and cold start running gave about 54-58 psi.

2) The fuel rail pressure at hot idle was in the 425 to 440 psi range and when moving varied between 600 psi and 1450 psi depending upon the amount of throttle and the engine RPM. On a good WOT pull the pressure climbed to 1800 - 2125 psi range. When coasting to a stop ( foot off the gas ) the fuel rail pressure briefly dropped to 280-350 psi range then returned to 425-440 range.
On a cold start the pressure was 1800-2050 for the first 30 seconds or so..

Hope these number can help you out.

 

[JRMF]

I didn't have time to get live data this weekend. I did get new module and low pressure sensor today, I also have not checked psi when hot, I'll keep you updated as soon as I get some free time to put some miles on with the psi tests. Thanks for helping me, I really appreciate it

 

[JRMF]

I had a few minutes to mess with the Terrain today. I replaced fuel low pressure sensor, I tried replacing the Fuel pressure module located in the rear hatch behind the drivers fender well. That's a no go until I can get someone to reprogram the car to the new module?? so just replacing the one sensor it didn't fix anything. My fuel pressure readings are right there with yours, if not exactly the same.

so I noticed while in gear, I can press the gas oh so lightly, maybe 1/8" and I can get the rpms to drop and make the motor stumble. hasn't stalled doing this but its close, still no codes off of that. I haven't been able to test drive it yet. i'll take it to work tomorrow and do some recordings.

 

[JRMF]

Ok I got the terrain to mess up halfway to work this morning... fuel pressure readings seemed alright, then threw the code with the high pressure only reading 195psi... I was able to clear the code while it was running and everything worked itself out besides the stabilitrak BS. When i put it in gear it stalled. But I couldn't get it to mess up on the 2nd half of the trip... maybe get in contact with the high pressure pump company and get a warranty swap?

 

[repairman54]

Did you use Genuine GM parts? Aftermarket electronic parts are not reliable.

 

[JRMF]

Did you use Genuine GM parts? Aftermarket electronic parts are not reliable.

I was not able to get a genuine GM pump at the time (from rockauto). I got "Standard" brand, which I've mostly had good luck. I am going to request a warranty exchange, but I'm unsure how that will work since the "Standard" brand is out of stock now... wish me luck

 

[Cwalter]

Im having the same exact issue with my 2014 Nox. Were you able to figure out the issue??

 

[testdis]

Same problem here with 2011 NOX....any updates or remedies?

 

[ex400rocks]

2013 terrain 2.4 When it starts to spit and sputter, my "desired" HPFS reads 0. Which doesn't make any sense, being as the vehicle is running. The PCM is wanting 0 psi... And this customer has replaced everything fuel related with all new GM parts. Wish me luck.

 

[Howardrific]

Did you find a fix? My 15' terrain slt-1 with 2.4 has started do this, mechanic says I need a new sensor. As I read on here and other places it's not the sensor.

 

[nick196606]

I'm having the same problem. I replaced the in tank pump and it fixed the low side pressure fluctuation. This is very aggravating as I have changed many parts with the exception of the throttle body. I'm kinda leaning towards pointing the blame at the Delphi hpfp. Is everyone else who's having this issue using an aftermarket hpfp? When the engine is warmed up at an idle it occasionally goes into a bit of surging then goes into limp mode.

 

[mkrager60]

2013 terrain 2.4 When it starts to spit and sputter, my "desired" HPFS reads 0. Which doesn't make any sense, being as the vehicle is running. The PCM is wanting 0 psi... And this customer has replaced everything fuel related with all new GM parts. Wish me luck.

ex400rocks, did you get this figured out? This is exactly what my 2013 Chevrolet Captiva is doing. I've replaced the hpfp, fuel rail pressure sensor, vvt solenoids.