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post #1 of 8 (permalink) Old 11-20-2012, 03:20 PM Thread Starter
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Running to Lean P0171

I have a 06 Chevy Cobalt LT 2.2 automatic and i cannot figure out for the life of me why this check engine light keeps coming on. I have checked for any leaks that could cause this, and did not find any. I bought the car a year ago with this problem and about 3 or so months ago i was visiting family in the city taking care of wedding stuff and all of a sudden i was driving down the road, gassed it to get through a light to keep up with my mom, right after i gassed it it went completely dead, after a week of having it at two seperate dealers the second dealer figured out the tcm had gone out. After replacing it til a week ago i had no problems now my light is coming on again. It has came on twice and is off now. I had read on the cobalt ss threads that it has something to do with the pcm? The stock programming is funky and really touchy, and it said it can be reprogrammed at a dealer to be fixed. Is that something i need to look into, or was the info i was reading bs? I dunno what to do and i want to get it fixed. I have no other ideas on this subject, maybe someone can help?
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post #2 of 8 (permalink) Old 11-20-2012, 03:31 PM
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First let me say Welcome to the site! Glad to see you did some searching first!

Do you have any mods done to the car at all? Also, GM from the factory actually runs their cars a little lean (for the sake of better gas mileage even tho it can cause LOTS of problems later on down the line). What all did the dealerships check if you know? Being lean and throwing that code could mean quite a few things actually. If it's instantly too lean, then you're front 02 sensor could be out, or your fuel filter could be clogged, or your fuel pump could be going out or your injectors could use a little cleaning or your TPS has come out of adjustment, or your MAF may need to be retuned. If it's throwing the code for being too lean for too long then it could be your rear 02 sensor. There are quite a few things that can be tested here and some can get quite expensive, so I'd try to figure out what the dealership checked.

Also a little more information about the problem would be very helpful. Does it pop the light on under hard throttles or no? Is it random? Does the light stay on or keep going off? How many miles on the car? What mods are done to the car?

Answer some of this and it will help to diagnose your problems .

'09 SS/TC - Stolen
Mods - Injen CAI, CIA MAF Relocate CP's, Dejon FMIC,
Custom 3" DP, 3" Exhaust, GT3076R, Pioneer AVH-4100DVD, Hurst STS, ZZP triple pod, Autometer Cobalt boost/DPIC/WB gauges, Nitto NT05 245/40/18's, H&R Springs, 80:20 Meth Spray
Future - KSport Kontrol Pro Coilovers, 10% Tint, FMIC spray
538whp/501wtq @38 psi on meth and 93 oct on stock ish motor


06 EVO IX MR/SE - Sold
Mods - *Updated 10/6/13* AEM TRUboost EBC, 4in custom TBE, SD dual 93/e85 tune, ETS 4in Race Core FMIC, Dual Aeromotive 400lph Fuel Pumps, T4 Tubular Manifold w/ dual WG's, FP Super99HTZ DBB Turbo, GSC 274 mivec cams, ARP headstuds/rod studs, FIC 2150cc Injectors, Aeromotive FPR, Aeromotive Fuel Rail, catch can, Mini Battery Kit, Slim Coolant Fan, Kiggly Racing high pressure valve Springs/Titanium Retainers, Supertech Stainless Steel Valves, Dual VTA Tial 44mm WG's, 4g64 Stroker Manley Pistons, 155mm 2.4 LR Manley Turbo Plus I Beam Rods with ARP 625 Studs, 100mm forged non-billet Manley Crankshaft, Full H/E PNP with Port Matching, Kiggly Racing Girdle, Dual Tial 50mm BOV's, Excedy Triple Disc Carbon HD Clutch, AEM EMS

'95 Ram 2500 Diesel
Mods - 5in TBE, Boost Elbow set to 28psi, Adjusted fuel pump, Open Turbo.

Future Mods- Super Street Clutch (rated @1400ftlbs tq), 67mm turbo, 160lb valve springs, added timing, tubular exhaust manifold, larger injectors, possible 6 spd swap.


Master ASE Certified Gasoline/Diesel Technician since 2004

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post #3 of 8 (permalink) Old 11-20-2012, 03:40 PM
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DTC P0171
Circuit Description
The powertrain control module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during Open Loop and Closed Loop. During Open Loop, the PCM determines fuel delivery based on sensor signals, without heated oxygen sensor (HO2S) input. During Closed Loop, the PCM adds HO2S inputs and level of purge to calculate the short and long term fuel trim adjustments. If the HO2S indicates a lean condition, the fuel trim values will be above 0 percent. If the HO2S indicates a rich condition, the fuel trim values will be below 0 percent. The short term fuel trim values change rapidly in response to the HO2S voltage signals. The long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. A block of cells contain information arranged in combinations of engine RPM and engine load for a full range of vehicle operating conditions. The long term fuel trim diagnostic is based on an average of cells currently being used. The PCM selects the cells based on the engine speed and load. If the PCM detects an excessively lean condition, DTC P0171 sets.

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post #4 of 8 (permalink) Old 11-20-2012, 04:55 PM
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Quote:
Originally Posted by Coby7 View Post
DTC P0171
Circuit Description
The powertrain control module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during Open Loop and Closed Loop. During Open Loop, the PCM determines fuel delivery based on sensor signals, without heated oxygen sensor (HO2S) input. During Closed Loop, the PCM adds HO2S inputs and level of purge to calculate the short and long term fuel trim adjustments. If the HO2S indicates a lean condition, the fuel trim values will be above 0 percent. If the HO2S indicates a rich condition, the fuel trim values will be below 0 percent. The short term fuel trim values change rapidly in response to the HO2S voltage signals. The long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. A block of cells contain information arranged in combinations of engine RPM and engine load for a full range of vehicle operating conditions. The long term fuel trim diagnostic is based on an average of cells currently being used. The PCM selects the cells based on the engine speed and load. If the PCM detects an excessively lean condition, DTC P0171 sets.
Nice! Glad you explained how each 02 sensor inputs directly to give your fuel trims (that is the biggest part of tuning right there, you're STFT's (short term fuel trims (off front pre-cat 02)), and LTFT's (long term fuel trims (post cat 02 sensor))).

'09 SS/TC - Stolen
Mods - Injen CAI, CIA MAF Relocate CP's, Dejon FMIC,
Custom 3" DP, 3" Exhaust, GT3076R, Pioneer AVH-4100DVD, Hurst STS, ZZP triple pod, Autometer Cobalt boost/DPIC/WB gauges, Nitto NT05 245/40/18's, H&R Springs, 80:20 Meth Spray
Future - KSport Kontrol Pro Coilovers, 10% Tint, FMIC spray
538whp/501wtq @38 psi on meth and 93 oct on stock ish motor


06 EVO IX MR/SE - Sold
Mods - *Updated 10/6/13* AEM TRUboost EBC, 4in custom TBE, SD dual 93/e85 tune, ETS 4in Race Core FMIC, Dual Aeromotive 400lph Fuel Pumps, T4 Tubular Manifold w/ dual WG's, FP Super99HTZ DBB Turbo, GSC 274 mivec cams, ARP headstuds/rod studs, FIC 2150cc Injectors, Aeromotive FPR, Aeromotive Fuel Rail, catch can, Mini Battery Kit, Slim Coolant Fan, Kiggly Racing high pressure valve Springs/Titanium Retainers, Supertech Stainless Steel Valves, Dual VTA Tial 44mm WG's, 4g64 Stroker Manley Pistons, 155mm 2.4 LR Manley Turbo Plus I Beam Rods with ARP 625 Studs, 100mm forged non-billet Manley Crankshaft, Full H/E PNP with Port Matching, Kiggly Racing Girdle, Dual Tial 50mm BOV's, Excedy Triple Disc Carbon HD Clutch, AEM EMS

'95 Ram 2500 Diesel
Mods - 5in TBE, Boost Elbow set to 28psi, Adjusted fuel pump, Open Turbo.

Future Mods- Super Street Clutch (rated @1400ftlbs tq), 67mm turbo, 160lb valve springs, added timing, tubular exhaust manifold, larger injectors, possible 6 spd swap.


Master ASE Certified Gasoline/Diesel Technician since 2004

Speed Junkies Social Group

Yourcobalt Official Facebook Page!

Syndicate of Tuners Official Page! Up and going again as of 1/11/13

Click here to PM me if you have questions or issues!
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post #5 of 8 (permalink) Old 11-20-2012, 08:10 PM Thread Starter
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No there are no mods to the car at the moment. All the dealership did as far as i know is figure out why my car wouldn't start and the problem for that was the tcm, they said they just go out on the cobalts. The light does just pop up at random the majority of the time and goes back off after a little further driving or a couple of days. The car has a little over 90,000 miles on it.

Quote:
Originally Posted by Leveecius View Post
First let me say Welcome to the site! Glad to see you did some searching first!

Do you have any mods done to the car at all? Also, GM from the factory actually runs their cars a little lean (for the sake of better gas mileage even tho it can cause LOTS of problems later on down the line). What all did the dealerships check if you know? Being lean and throwing that code could mean quite a few things actually. If it's instantly too lean, then you're front 02 sensor could be out, or your fuel filter could be clogged, or your fuel pump could be going out or your injectors could use a little cleaning or your TPS has come out of adjustment, or your MAF may need to be retuned. If it's throwing the code for being too lean for too long then it could be your rear 02 sensor. There are quite a few things that can be tested here and some can get quite expensive, so I'd try to figure out what the dealership checked.

Also a little more information about the problem would be very helpful. Does it pop the light on under hard throttles or no? Is it random? Does the light stay on or keep going off? How many miles on the car? What mods are done to the car?

Answer some of this and it will help to diagnose your problems .
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post #6 of 8 (permalink) Old 11-24-2012, 09:10 AM
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Welcome to the forum, Shay!

You're already getting solid feedback from the community and I wish you success in getting this addressed. I'm here to assist if you have any questions about warranty or recall information, and can also work with you and your dealership if you decided to go that route.

I will see you around the forum, and if you have any questions for me don't hesitate to ask!
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Have you checked into Chevrolet Owner Center? You can maintain service history, check on warranty or recall information, and more. Visit my.chevrolet.com!
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post #7 of 8 (permalink) Old 11-24-2012, 09:18 AM
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Ok, I know cycling the key on and off a few handfuls of times will actually reset the CEL on the car. However it doesn't delete the code. So if it's still throwing the codes, I would first start by putting some Sea Foam into your fuel tank (a whole can) on your next tank fill up. Let it run through the whole tank and see what happens from there. If you are still getting the light to come on at random times I would suggest getting your Cat checked as well as your Rear 02 sensor as that is usually the one that goes out if you're not hard on your throttle all the time. That would be about all I can suggest as of right now.

'09 SS/TC - Stolen
Mods - Injen CAI, CIA MAF Relocate CP's, Dejon FMIC,
Custom 3" DP, 3" Exhaust, GT3076R, Pioneer AVH-4100DVD, Hurst STS, ZZP triple pod, Autometer Cobalt boost/DPIC/WB gauges, Nitto NT05 245/40/18's, H&R Springs, 80:20 Meth Spray
Future - KSport Kontrol Pro Coilovers, 10% Tint, FMIC spray
538whp/501wtq @38 psi on meth and 93 oct on stock ish motor


06 EVO IX MR/SE - Sold
Mods - *Updated 10/6/13* AEM TRUboost EBC, 4in custom TBE, SD dual 93/e85 tune, ETS 4in Race Core FMIC, Dual Aeromotive 400lph Fuel Pumps, T4 Tubular Manifold w/ dual WG's, FP Super99HTZ DBB Turbo, GSC 274 mivec cams, ARP headstuds/rod studs, FIC 2150cc Injectors, Aeromotive FPR, Aeromotive Fuel Rail, catch can, Mini Battery Kit, Slim Coolant Fan, Kiggly Racing high pressure valve Springs/Titanium Retainers, Supertech Stainless Steel Valves, Dual VTA Tial 44mm WG's, 4g64 Stroker Manley Pistons, 155mm 2.4 LR Manley Turbo Plus I Beam Rods with ARP 625 Studs, 100mm forged non-billet Manley Crankshaft, Full H/E PNP with Port Matching, Kiggly Racing Girdle, Dual Tial 50mm BOV's, Excedy Triple Disc Carbon HD Clutch, AEM EMS

'95 Ram 2500 Diesel
Mods - 5in TBE, Boost Elbow set to 28psi, Adjusted fuel pump, Open Turbo.

Future Mods- Super Street Clutch (rated @1400ftlbs tq), 67mm turbo, 160lb valve springs, added timing, tubular exhaust manifold, larger injectors, possible 6 spd swap.


Master ASE Certified Gasoline/Diesel Technician since 2004

Speed Junkies Social Group

Yourcobalt Official Facebook Page!

Syndicate of Tuners Official Page! Up and going again as of 1/11/13

Click here to PM me if you have questions or issues!
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post #8 of 8 (permalink) Old 11-24-2012, 10:19 PM
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There are so many things that could throw a lean code. Leak behind your MAF, brake booster leak, Intake manifold gasket, EGR problem, exhaust leak just to name a few easy suspects. Like mentioned above, any mods or maintenance done lately etc? Sorry..Edit.. saw no mods...

Last edited by scagnetti76; 11-24-2012 at 10:22 PM.
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