P0171 and P0174 - Stabilitrak...only under certain conditions.

Jimxms · Sep 19, 2024

I purchased an 07 Esky a few weeks back and managed to get a bit of a discount as it had a CEL due to failed o2 sensors (heater circuit codes - P0030 P0050 P0053 P0059). I just figured that it needed some new o2 sensors, so I went and replaced all 4 with genuine Bosch items from rockauto. This fixed the codes.

However, now when i drive the truck I occasionally get a 'stabilitrack bing' and a new code set for lean bank 1, 2 or both (p0171 p0174. Even with the code set the bing continues to occur as I drive, and generally under these conditions:

- when going up a long steep gradient at a constant rpm.
- when towing (it happens constantly when towing)

No other codes are set.

It does not occur when the car is idling or if i hold the revs high in park, it also doesn't occur if I floor it and drive it around like I stole it.

My OBD scanner shows STFT (fuel trims) at 0 - 1 for both banks at idle, and around -2 - 10 when driving. Occasionally going as high as 14. LTFT's are both at 0 though.

I cant hear any vacuum leaks at idle and as the fuel trims are 0 it seems to indicate there isnt one. My only thought is that my rusty exhaust manifolds are maybe allowing air to be sucked in - but only when the engine is under heavy load and maybe leaning (worn engine mounts?) for long enough for the o2 sensors to get a good steady sample of the air and set a code?

Does this sound plausible, has anyone else had a similar issue?

Jimxms · Sep 19, 2024

The only other odd thing I've noticed is that my H02S Bank 2 Sensor 2 stays at a value of around 300mv, whereas the Bank 1 Sensor 2 is steady around 700mv. That said, these are post-cat sensors so shouldn't play any part in the engine fuelling right?

B1S1 and B2S1 jump between 99-800mv

j91z28d1 · Sep 19, 2024

are all the exhaust manifold bolts there? it's pretty common to have a one pop the head off and have an exhaust leak that can suck in air.

the r other thing I see is the Bosch sensors. there's a few threads floating around where these some of these trucks basically act up with anything but the oem o2 sensors. even the DENSO which makes the o2 sensors for acdelco have had issues. usually some kinda performance code. I don't remember exactly and I haven't looked up what your codes mean. Just off the top of my head. that and aftermarket air boxes and filters like to cause issues some times too.

Jimxms · Sep 20, 2024

As far as I can tell I still have all of the exhaust bolts. However the manifolds look like the titanic with big chunks of rust flaking off.

I’ve held a piece of paper all around the manifold while the engine was idling to see if a slight leak could be detected, but there was nothing. I may try blocking the exhaust with a rag tomorrow to see if additional pressure reveals a small leak some more.

That’s annoying about the Bosch sensors. I thought I was buying the best

swathdiver · Sep 20, 2024

Jimxms said:
I purchased an 07 Esky a few weeks back and managed to get a bit of a discount as it had a CEL due to failed o2 sensors (heater circuit codes - P0030 P0050 P0053 P0059). I just figured that it needed some new o2 sensors, so I went and replaced all 4 with genuine Bosch items from rockauto. This fixed the codes.

These codes are generally indicative of a wiring issue such as a critter munching on the wires or a bad ECM. That being said, you may have a cat on its way out. If the downstream sensors move a lot, that's indicative of a failed cat. Slow and steady is normal.

Have you inspected your plugs and wires yet?

Jimxms · Sep 20, 2024

swathdiver said:
These codes are generally indicative of a wiring issue such as a critter munching on the wires or a bad ECM. That being said, you may have a cat on its way out. If the downstream sensors move a lot, that's indicative of a failed cat. Slow and steady is normal.

Have you inspected your plugs and wires yet?

I've put in new plugs, wires and coils (just for general maintenance). The old plugs looked fine, but possibly a little like the car was running on the lean side (like the codes suggest). I'm gonna smoke test the intake later today to look for any leaks but I have a feeling that if its only setting the lean codes under certain conditions it's probably not going to reveal anything.

Jimxms · Sep 21, 2024

So I just smoke tested the intake etc and the only thing that showed any sign of leaking was the oil filler spout. It wouldn’t sit properly so I removed it and put the soul cap directly on it instead

I doubt this is the cause, but I’ll take it for a test and report back

Doubeleive · Sep 21, 2024

Jimxms said:
I purchased an 07 Esky a few weeks back and managed to get a bit of a discount as it had a CEL due to failed o2 sensors (heater circuit codes - P0030 P0050 P0053 P0059). I just figured that it needed some new o2 sensors, so I went and replaced all 4 with genuine Bosch items from rockauto. This fixed the codes.

However, now when i drive the truck I occasionally get a 'stabilitrack bing' and a new code set for lean bank 1, 2 or both (p0171 p0174. Even with the code set the bing continues to occur as I drive, and generally under these conditions:

- when going up a long steep gradient at a constant rpm.
- when towing (it happens constantly when towing)

No other codes are set.

It does not occur when the car is idling or if i hold the revs high in park, it also doesn't occur if I floor it and drive it around like I stole it.

My OBD scanner shows STFT (fuel trims) at 0 - 1 for both banks at idle, and around -2 - 10 when driving. Occasionally going as high as 14. LTFT's are both at 0 though.

I cant hear any vacuum leaks at idle and as the fuel trims are 0 it seems to indicate there isnt one. My only thought is that my rusty exhaust manifolds are maybe allowing air to be sucked in - but only when the engine is under heavy load and maybe leaning (worn engine mounts?) for long enough for the o2 sensors to get a good steady sample of the air and set a code?

Does this sound plausible, has anyone else had a similar issue?

do or have a backpressure test performed, my conditions similar or same as yours above was a due to a clogged cat, that would explain both the misfire, lean and 02 codes
testing thru a bank 1 02 sensor bung, normal psi is 2.5 (max)
mine was reading 5 at idle and 10 with throttle applied.
the problem started showing when the vehicle was under a load, going up a big hill or anytime above 80-85mph and trying to pass, etc
at idle and driving normal around the city, cruising at 60-70 on the highway zero issue
fuel trims were normal or exceptionally good, when diagnosing knock retard/misfire would occur under a load.
when it got worse stabiltrac would flash only when heavy misfire happened along with flashing cel, upon no load both would go away

Jimxms · Sep 21, 2024

Doubeleive said:
do or have a backpressure test performed, my conditions similar or same as yours above was a due to a clogged cat, that would explain both the misfire, lean and 02 codes
testing thru a bank 1 02 sensor bung, normal psi is 2.5 (max)
mine was reading 5 at idle and 10 with throttle applied.
the problem started showing when the vehicle was under a load, going up a big hill or anytime above 80-85mph and trying to pass, etc
at idle and driving normal around the city, cruising at 60-70 on the highway zero issue
fuel trims were normal or exceptionally good, when diagnosing knock retard/misfire would occur under a load.
when it got worse stabiltrac would flash only when heavy misfire happened along with flashing cel, upon no load both would go away

Interesting you should say that as I was laying awake last night thinking I should check the cats because the previous owner drove the car for a LONG time with dead 02 sensors...to the point he disconnected the CEL.

I noticed this discrepancy in the post-cat readings for the left and right bank on my scantool:

I'm somewhat of a newbie to this, but am i right in saying that the B1S2 and B2S2 sensors should be reading somewhat similar voltages if the cats are both working the same? B2S2 potentially being lean with a ~300mv constant reading?

EDIT: I've got a fuel pressure gauge on the way to test the fuel rail psi, but i'll also use it to test backpressure on the cats. Thanks for the suggestion.

Doubeleive · Sep 21, 2024

bank2 looks off, for the backpressure test you would need to either buy a tool or make one
it would just take say a pipe fitting that fits in the 02 bung, hose and a low pressure psi gauge
I think the tool just has nozzle fitting that you stick in the forward 02 sensor bung
looks like harbor freight sells a tool for $35

https://www.harborfreight.com/engine-and-transmission-oil-pressure-test-kit-64872.html?event_id=183642&utm_source=google&utm_medium=cpc&utm_campaign=17890472041&campaignid=17890472041&utm_content=140972256953&adsetid=140972256953&product=64872&store=3091&gad_source=1&gclid=Cj0KCQjw3bm3BhDJARIsAKnHoVUH8A5CTuf4pWpfDBmBRKSj3rQLn3afg92-vCsAbmL2BUSu6s4P-o0aAkhhEALw_wcB

P0171 and P0174 - Stabilitrak...only under certain conditions.

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