Help diagnosing p1175 on 2008 6.2

[cameronc]

I've diagnosed issue with scanner for months now trying to fix problem without success. I've replaced parts I didn't think were bad but I don't know what else to do to fix. Replaced o2 sensors with genuine gm. Tune up. Replaced fuel injectors. Checked for vacuum leaks. Tested fuel pressure. The freeze frame data when the code sets don't seem out of range to me. Both banks seem normal. The fuel trims are good and the maf is in range. No misfire codes at all although it has had a rough idle since I purchased 3 years ago with 100k on it. Now has 140k. Runs great just rough idle. Misfire data on scanner doesn't show anything out of range on either bank. I have more info if someone interested in helping. Thanks 

[Bleepster]

try new plugs/wires/coils?

[redvett]

Code P1175 Chevrolet Tech Notes The P1175 code sometimes is triggered by clogged fuel injectors. Start by using high octane fuel and/or fuel additive to clean injectors. If the problem persists fuel injectors may need to be replaced. There is a Factory Service Bulletin for all 2000-2013 Chevrolet models: 2000-2013 Chevrolet Factory Service Bulletin OBDII Code P1175

Read more: https://www.autocodes.com/p1175_chevrolet.html

[Bleepster]

2 hours ago, redvett said:

Code P1175 Chevrolet Tech Notes The P1175 code sometimes is triggered by clogged fuel injectors. Start by using high octane fuel and/or fuel additive to clean injectors. If the problem persists fuel injectors may need to be replaced. There is a Factory Service Bulletin for all 2000-2013 Chevrolet models: 2000-2013 Chevrolet Factory Service Bulletin OBDII Code P1175

Read more: https://www.autocodes.com/p1175_chevrolet.html

he replaced fuel injectors and verified fuel pressure.

[richard wysong]

Possibly carbon build=up on the intake valves?

[cameronc]

Already replaced plugs, wires, and injectors. Scanner doesn't pick up any misfires out of range. I haven't done a leak down compression test on bank 2 yet. Thats my next step but I just don't understand why the code sets because the freeze frame data shows bank 1 and 2 both very close and not crazy lean. Also ran seafoam upper intake cleaner through intake but I'm not going to say that definitely cleaned carbon. 

Edited September 6, 2023 by cameronc

[Bleepster]

coils?

[newdude]

static.nhtsa.gov/odi/tsbs/2022/MC-10219266-0001.pdf

 

DTC P1174 or P1175
DTC P1174
Fuel Trim Cylinder Balance Bank 1
DTC P1175
Fuel Trim Cylinder Balance Bank 2
Circuit/System Description
The Fuel Trim Cylinder Balance diagnostic detects a rich or lean cylinder to cylinder air/fuel ratio imbalance in each bank. The diagnostic monitors the pre-catalyst heated oxygen sensor (HO2S) signal's frequency and amplitude characteristics by calculating an accumulated voltage over a predetermined sample period. An imbalance is indicated when multiple samples of the accumulated voltage are consistently higher than the desired value.
Conditions for Running the DTC

DTCs P0030, P0036, P0050, P0053, P0059, P0101, P0102, P0103, P0106, P0107, P0108, P0117, P0118, P0128, P0131, P0132, P0133, P0134, P0135, P0151, P0152, P0153, P0154, P0155, P0201–P0206, P0300, P0301–P0306, P0411, P0412, P0418, P0442, P0443, P0446, P0449, P0452, P0453, P0454, P0455, P0496, P1133, P1153, P1516, P2101, P2119, P2120, P2125, P2135, P2138, P2176, P2431, P2432, P2433, P2440, P2A00, P2A03 are not set.

The device control is not active.
The intrusive diagnostics are not active.
The engine overspeed protection is not active.
The power take-off (PTO) is not active.
The traction control is not active.
The fuel control is in air-fuel Closed Loop.
The system voltage is more than 10 volts, or less than 18 volts.
The engine run time is greater than 100 seconds.
The engine coolant temperature (ECT) is greater than −20°C (−4°F).
The engine speed is greater than 425 RPM, but less than 6,000 RPM.
The mass air flow is greater than 25 g/s, but less than 510 g/s.
Conditions for Setting the DTC
Multiple samples of the pre-catalyst HO2S accumulated voltage are consistently greater than the desired value.
Action Taken When the DTC Sets
DTCs P1174 and P1175 are Type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P1174 and P1175 are Type B DTCs.

Diagnostic Aids
The fuel trim cylinder balance diagnostic is very sensitive to heated oxygen sensor (HO2S) design. A non-OE sensor or an incorrect part number may cause a DTC to set.

Monitoring the misfire current counters, or misfire graph, may help to isolate the cylinder that is causing the condition.

Two or more fuel injectors on one bank skewed in the same direction may cause a DTC to set, even if they pass the fuel injector balance test.

Circuit/System Testing
Read and record the Freeze Frame/Failure Records data taking note of the speed and load at which the DTC set.
Diagnose any other DTCs that are set. Refer to Diagnostic Trouble Code (DTC) List - Vehicle.
With the engine idling and the transmission in the Park or Neutral position, observe the manifold absolute pressure (MAP) sensor parameter. The MAP sensor parameter should be between 19–42 kPa.
If the MAP sensor parameter is not between 19–42 kPa, refer to DTC P0106 or DTC P0107 or P0108.

Inspect the air induction system for modified, damaged, leaking, or restricted components.

Inspect the crankcase ventilation system for improper operation.

Inspect the vacuum hoses for splits, kinks, and improper connections.

Inspect for vacuum leaks at the intake manifold, the throttle body, and the injector O-rings.

Test for a restricted, damaged, leaking, or modified exhaust system from the catalytic converter forward. Refer to Symptoms - Engine Exhaust.
Test the fuel injectors for improper operation. Refer to Fuel Injector Diagnosis.

Test for fuel contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis.

Test for fuel composition error, FlexFuel/E85, only. Refer to Fuel Composition Diagnosis.

Test for excessive fuel in the crankcase due to leaking injectors.

Test the ignition system for improper operation. Refer to Electronic Ignition System Diagnosis.

Test the engine for any mechanical conditions such as sticking valves, lifters, etc., which could alter the flow into the combustion chamber. Refer to Symptoms - Engine Mechanical.

Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verify the repair under the same speed and load as noted in the Freeze Frame/Failure Records data recorded during testing.

[cameronc]

Well here's results from today's testing.

Fuel pressure koeo 64psi, idling 44psi.

Compression bank 2-Full throttle, 4 revolutions.

#2 220psi, #4 225psi, #6 230psi, #8 230psi

Double checked plug gap at .040

Ecm is in control of fuel trims. Both banks run between -5.0 & +5.0. I can pump brakes and drive both banks lean and add fuel to intake and drive them rich. B1s1 and b2s1 ho2 both steady switching. Maf graph is steady consistent with throttle pedal.

[rdartua]

On 9/4/2023 at 10:24 PM, cameronc said:

eplaced fuel injectors. Checked for vacuum leaks. Tested fuel pressure. The freeze frame data when the code sets don't seem out of range to me. Both banks seem normal. The fuel trims are good and the maf is in range. No misfire codes at all although it has had a rough idle since I purchased 3 years ago with 100k on it. Now has 140k. Runs great just rough idle. Misfire data on scanner doesn't show anything out of range on either ban

Dude - any luck figuring this out? I have same damn issue on 6.2l 2008 Denali - took same course of action across the board - even replaced exhaust manifold with new gm gasket. I do run NTK o2 sensors though - all 4. Not sure if this could cause an issue. honestly maybe we sould use O2 sensor extension tube?

[X-man]

On 9/4/2023 at 7:24 PM, cameronc said:

I've diagnosed issue with scanner for months now trying to fix problem without success. I've replaced parts I didn't think were bad but I don't know what else to do to fix. Replaced o2 sensors with genuine gm. Tune up. Replaced fuel injectors. Checked for vacuum leaks. Tested fuel pressure. The freeze frame data when the code sets don't seem out of range to me. Both banks seem normal. The fuel trims are good and the maf is in range. No misfire codes at all although it has had a rough idle since I purchased 3 years ago with 100k on it. Now has 140k. Runs great just rough idle. Misfire data on scanner doesn't show anything out of range on either bank. I have more info if someone interested in helping. Thanks 

I don’t know if this will help but I received a letter in the mail from GM years ago, it was in ref. to vehicles equipped with V8 engines may have condition where the throttle position sensor may cause the engine to run rough and cause the malfunction indicator lamp/or engine reduced power message to illuminate.

GM would replace the throttle body if these symptoms occurred. This was only good for a limited time and mileage so it has expired by now.

It may be worth checking this out. 
 

[swathdiver]

On 4/2/2024 at 3:21 PM, rdartua said:

Dude - any luck figuring this out? I have same damn issue on 6.2l 2008 Denali - took same course of action across the board - even replaced exhaust manifold with new gm gasket. I do run NTK o2 sensors though - all 4. Not sure if this could cause an issue. honestly maybe we sould use O2 sensor extension tube?

 

These trucks do not take kindly to aftermarket oxygen sensors, use GM OE only.

[AJ Fitz]

I have a 2009 Chevy Silverado 1500 6.2 flex fuel I've been running codes off and on for about 6 months to a year it's ridiculous I've done all kinds of things to try to fix my truck it all started with a bad rusted fuse for the fuel pump control module which took a while to figure that out cuz the fuse tested fine that was causing my truck not to start sometimes and then I've been getting Bank to running lean for a while and I got a ridiculous quote for the fuel injectors of 2400 I replaced them myself and saved a lot of money and that got the codes off and the truck started running good for about 3 days and then now it's running bad again and it's like breathing hard when it shift gears and it's losing a lot of horsepower when I accelerate and it's a code came up p 0 1 1 7 5 gm DTC definitions not found I replaced all kinds of stuff on this car the purge valve the canister the canister solenoid the filter every part of the EVAP system I've replaced I replaced all the fuel injectors I got a new starter which went bad there's a screw this seems like there's a lot of screws missing on the manifold like there's four spots where it looks like there could be a bolt but there's nothing there I don't know if those holes are supposed to be there or not I may sound down but I'll have to take some pictures and add it to this post soon but it's a nightmare lately with this truck it's always something I don't know what to do I'm thinking maybe the next thing I got to do is replace the fuel filter and the fuel pump I don't know what to do anybody can help me I'd really appreciate it possible maybe the fuel pump control module needs to be replaced I don't know where I was seeing O2 sensor someone please help me

[richard wysong]

Welcome to the Forum! check the fuel pressure and volume

[AJ Fitz]

5 hours ago, richard wysong said:

Welcome to the Forum! check the fuel pressure and volume

The fiel pressure goes from 40-42 idling and to 44-46 when driving