I have a 2006 Monte ls with the 3.5 v6. And for just short of a year i've had a check engine light on. I hooked it up to a code reader and it gave the code P1174. So some time whent by and my stock muffler rusted out so I replaced it with a flowmaster super 40 muffler. Just 3 days ago I got my tax return and decided to repair the check engine light. I took the car to the local chevy dealership and they said that the flowaster was causeing the check engine light to come on and that to clear the code I would have to buy the 600$ stock exaust system. Allthough the code was on when the stock exaust was still good. Im seriously doubting that the flowmaster muffler is causeing this problem because if it was then every person on this forum whould have this code showing. And according to other opinions I have gotten, this code dosent relate to the exaust. Is there anyone out there who has any idea what is going on with my car because I dont want to rip off my flowmaster and put on the stock system. After three days of fighting the dealership I am so frustrated and I dont know what to do. I actually have the feeling that the dealership didnt want to spend the time on it so they just saw the new muffler and said ohh aftermarket thats it.

 

check for a vacuum leak somewhere...

P1174 = Fuel Trim Adaptation Inactive Bank 1 Malfunction

also, here's the GM service info about getting that DTC:

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Service Information
2006 Chevrolet Impala | Impala, Monte Carlo (VIN W) Service Manual | Document ID: 1618983
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DTC P1174
DTC Descriptor
DTC 1174: Air Fuel Imbalance Bank 1


Diagnostic Fault Information
Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

System Description
The air fuel imbalance monitor (AFIM) diagnostic detects a rich or lean cylinder to cylinder air/fuel ratio imbalance. An imbalance will result in oxygen sensor signal switching above the desired frequency. Diagnostic detection is accomplished by measuring the frequency of the pre-catalyst oxygen sensor signal. If the frequency of the oxygen sensor signal exceeds the calibrated limit, a failure is reported.

Conditions for Running the DTC
• DTCs P0030, P0036, P0101, P0102, P0103, P0106, P0107, P0108, P0117, P0118, P0128, P0131, P0132, P0133, P0134, P0135, P0201-P0206, P0300, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0496, P1133, P1516, P2101, P2119, P2120, P2125, P2135, P2138, P2176, P2A00, are not set.

• The device control is not active.

• The intrusive diagnostics is 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 greater than 10 volts, or less than 18 volts.

• The engine run time is greater than 50 seconds.

• The engine coolant temperature (ECT) is greater than 10°C (50°F).

• The engine speed is greater than 1,000 RPM, but less than 4,000 RPM.

• The mass air flow is greater than 7 g/s, but less than 400 g/s.

Conditions for Setting the DTC
The air-fuel imbalance is monitored for a predetermined amount of time before the DTC sets.

Action Taken When the DTC Sets
• The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

• The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
• The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

• A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• Clear the MIL and the DTC with a scan tool.

Reference Information
Schematic Reference
Engine Controls Schematics

Electrical Information Reference
• Circuit Testing

• Troubleshooting with a Test Lamp

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs

Scan Tool Reference
• Scan Tool Data List

• Scan Tool Output Controls

Special Tools Required
• J 34730-1A Fuel Pressure Gage

• J 39021 Fuel Injector Coil and Balance Tester

• J 39021-210 Injector Tester Adapter Box

• J-39021-450 Fuel Injector Harness Adapter

Circuit/System Testing
Important: If any DTCs other than DTC P1174 is also set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

• Inspect the air intake system for the following:

- Modified, damaged, or restricted components

- Dirty or deteriorating air filter element

• Test fuel injector balance for a rich or lean condition. Refer to Fuel Injector Diagnosis .

• Inspect the base engine for the following:

- The crankcase ventilation system for correct operation.

- A vacuum leak and other un-metered air downstream of the mass air flow (MAF) sensor

- The intake manifold for a leak

• Inspect the exhaust system for the following:

- An exhaust leak

- Damaged, restricted, modified or enhanced exhaust system.

• Inspect the engine mechanical for items that could alter the air flow into the combustion chamber.
© 2008 General Motors Corporation. All rights reserved.

 

Wow thanks, so do you're pretty shure its a vac leak? I looked around the engine compartment and did'nt find much but I did'nt check everything. Is there somewhere spicific that I should look. I took apart the air intake box and there was what seemed to be a foam gasket missing I was'nt shure if that would cause it tho. You would think that the 90 dollar diagnostic fee whould include checking for a vac leak, but then again maybee not. In addition my transmission seems to shift hard through all 6 gears for about 10 minutes every week or two. Do you have any insight about that? Anything you have will help. Plus if anyone else looks at this and has an idea it would be very appreciated if you can share it.

 

the hard shifting could be the flex plate in the tranny... another guy on another forum had the same issue - with his SS tho, and did some testing/discovery on a dyno... here's what he found out:

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The 06 LS4 has a 6 bolt flex plate and later models have a 8 bolt.

As it turns out the flex plate is flexing just enough to allow a small amount of air to pass into the tranny fluid, thus causing the shudder and hard shifts at times due to a computer call for higher pressure.

 

Is there anyway to fix that?

 

Well, (on the orignial issue) it could be a vacuum leak, but that's not all it could be. Plus, if it was a significant vacuum leak you would probably notice it in other ways like poor idling and possibly even vacuum noise, but that is iffy.

I had a similar problem with my 02 along with other codes that developed from a bad thermostat. Things didn't heat up properly so the comparisons the electronics did were thrown off and several codes got wrapped up in the process. Only once have I ever had a vacuum leak bad enough to throw a code and I have over 180,000 miles on the car. That one time was due to a back fire that blew the line to the pressure regulator off the throttle body. Found that quick enough, popped it back in place - no issues. I actually caught that before it ever threw a code and I had run it for two days with the line off. I was really pretty surprised it would even run.

Anyway, for me, the first thing I would do is clear the code. You've been running it this long it won't hurt. If the problem does still exist, the code will come back soon enough. If the code doesn't come back so much the better. The condition that threw the code may be gone already.

Food for thought.

 

Ok so heres an update. Been looking for a vac leak and cant seem to find one but I can hear a whistle once and a while. My check engine light came on not but a few hours after I left the dealership and stayed on for a week but went off for about an hour and then came back on for about and hour or so and then just went off and hasent came back on but I have a feeling it will come back on again.

 

Just run down to Sears or Walmart and get an OBD II scanner that has the ability to clear the code. Costs 70 - 100 bucks.