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post #1 of 12 (permalink) Old 03-09-2010, 10:55 PM Thread Starter
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My CEL Engine Codes-How to Rid Them.

P0304-Misfire on cylinder 4
P0497-EVAC Low Purge
P2261-Intake

What are these and how do I fix em? Techs and mechanics chime in. Thx.

*Also, side question.... how much pressure is put on the engine coolant system? I know its under pressure, but how serious is it? And does that pressure change with increased RPM or engine heat or what?--I guess a basic rundown of how the coolant flows through the system from the resivoir would be nice. Thx again.
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post #2 of 12 (permalink) Old 03-09-2010, 11:06 PM
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A P0304 code means that the the car's computer has detected that one of the engines cylinders is not firing properly. In this case it's cylinder #4.

Symptoms may include:
  • the engine may be harder to start
  • the engine may stumble / stumble, and/or hesitate
  • other symptoms may also be present

A code P0304 may mean that one or more of the following has happened:
  • Faulty spark plug or wire
  • Faulty coil (pack)
  • Faulty oxygen sensor(s)
  • Faulty fuel injector
  • Burned exhaust valve
  • Faulty catalytic converter(s)
  • Running out of fuel
  • Poor compression
  • Defective computer

P0497-EVAC Low Purge

This DTC tests for proper intake manifold vacuum flow to the evaporative emission (EVAP) system. The engine control module (ECM) opens the EVAP canister purge solenoid valve and closes the EVAP canister vent solenoid valve. The ECM then monitors the fuel tank pressure (FTP) sensor to determine if a vacuum is being drawn on the EVAP system. If vacuum in the EVAP system is less than a predetermined value within a predetermined time, this DTC sets.



P2261-Intake

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PI: LNF- Intermittent DTC P2261
Service Information
2009 Chevrolet Cobalt | Cobalt, G5 (VIN A) Service Manual | Preliminary Information | Document ID: 2324723
--------------------------------------------------------------------------------

#PIP4669A: Intermittent DTC P2261 Setting - (Aug 10, 2009)


Subject: Intermittent DTC P2261 Setting


Models: 2008-2010 Chevrolet Cobalt SS

2008-2010 Chevrolet HHR SS




--------------------------------------------------------------------------------

This PI was superseded to update model years. Please discard PIP4669.


--------------------------------------------------------------------------------

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
A technician may find DTC P2261: Turbocharger Bypass Valve Stuck Closed set with no problem found. It may be intermittent in nature or they may find the dtc will set after a hard acceleration, usually in third gear. DTC P2261 is a type B dtc and will not set on the first drive cycle the dtc sets, therefore multiple test drives should be performed to confirm repair.

Recommendation/Instructions:
SI diagnostics for this DTC states that the ECM compares the measured MAF reading to the modeled MAF and has detected a series of pulsations in the induction system that exceed a calibrated threshold. A snapshot of "Induction Data" will show the fault, however the tech may need to compare the snapshot data to another vehicle if they are unfamiliar with the readings. They should note a fluctuation and or a difference in the desired versus requested boost level. When diagnosing this dtc pay close attention to Circuit/System testing step #1. This step has you inspecting for any vacuum leaks, damage, restrictions, improper routing or connecting of the vacuum hoses on the charge air bypass valve solenoid, the charge air bypass valve, and the charge air bypass valve vacuum tank.

We have found leaking vacuum tanks causing this dtc. When testing the vacuum tank, care must be used or the results may not be valid. The vacuum tank has an integral check valve not noted in SI. To check the Vacuum Tank operation, disconnect the hose that runs from the tank to the Bypass Valve Solenoid at the solenoid and apply vacuum to the tank. The tank should be able to maintain vacuum with no decay. Note: If you remove the vacuum hose from the intake manifold and plug it and the decay stops the check valve is leaking, if the decay continues the tank itself is leaking.

Note: Front wheel drive platforms using the 2.0 Liter RPO (LNF) incorporate a charge air bypass valve supplemental vacuum tank. The purpose of the tank is to provide an instant source of vacuum to the bypass valve via the bypass solenoid (when it is commanded open by the ECM). This results in less pressure buildup under closed throttle conditions, thereby reducing compressor noise, surge and spool time.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION


2009 General Motors Corporation. All rights reserved.
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Conditions for Setting the DTC
• The ECM detects weak vacuum during a purge condition.

• The fuel tank vacuum is less than -1 inches H2O for 4 seconds continuously or 50 seconds cumulative, within 10 minutes of cold start.

• The 11 second test can run up to 10 times within 10 minutes of cold start and must be completed before this DTC will set.

---------- Post added at 02:06 AM ---------- Previous post was at 02:05 AM ----------

I found that info on Google...




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post #3 of 12 (permalink) Old 03-10-2010, 01:18 AM
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For one, check your spark plugs, if not upgrade them to NGK BRK7E Spark Plugs, those should help with your cylinder misfire...

The coolant system builds pressure as the temperature of your car rises, it never really gets above like 18 PSI, in your coolant resevoir, as for everything else it is up in the air, if your system is warm or hot, and you open your surge tank cap, it will overflow because of the pressure, that is why it says not to open when hot lol, because of the pressure and possible burns one could recieve.

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post #4 of 12 (permalink) Old 03-10-2010, 04:54 AM
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Your Rad cap is what controls the cooling system pressure.
GM uses 16 lbs rad caps on our cars...
Pressure gets higher when hot, but not over 16
if your rad cap is in working order.

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post #5 of 12 (permalink) Old 03-10-2010, 06:19 PM Thread Starter
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OK, got back from the dealership..... money is skimpy in my wallet these days so I skipped any CEL codes with the dealer and just went with a Package deal, their "Diagnostic fee" and figure out the Low coolant........

And of course ive voided my warranty since I have a bunch on new shiny stuff under the hood---But anyway, they pressure tested and there is a crack in my radiator.... and its totally obvious to me and the dealership dude that its a stress crack, or something like that...... but I cant play it off as normal wear and tear on a 2009 SS even though I know I didnt crack the darn thing.

Anyway, I said thanks but no thanks... not shelling out 1000 bucks for a new OEM radiator and labor. Either I go aftermarket, or I just JB/Putty weld that crack and seal it now that i know were the leak is.

HELP--QUESTION: Ok, so the coolant system stays at a constant pressure or does it fluctuate? Im worried that since im running added boost that installing a NEW OEM radiator.... or OEM LIKE radiator that it will just crack under added pressure as well.... IS THIS THE CASE?--AND IF SO THAT MEANS I NEED TO GO WITH AN AEM RADIATOR?

Q1-Just Putty/epoxy the crack to fix er up?

Q2-Where can I find a high performance radiator that will fit---Added boost, so its gotta be aluminum with no plastic.


WHATS YOUR TAKE ON THIS SITUATION?
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post #6 of 12 (permalink) Old 03-10-2010, 08:45 PM
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I would say fix it for right now and then get a new oem one or one that is like it. The pressure in the coolant system doesn't fluctuate, but it isn't constant until an "appropriate" operating temperature is reached where the pressure gets up there.

If you fix it for right now, try to keep out of boost and "PE" and just grandma the thing and then go from there, that is all you really can do, because, it could just be me, I don't think I would want to drive around with just a repaired radiator, knowing something isn't fixed fully.

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post #7 of 12 (permalink) Old 03-10-2010, 09:14 PM
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Boost doesn't effect your coolant pressure. If the system exceeds a certain pressure it will exhaust through the overfill tank or vent tube.

I would get the new factory radiator. It didn't break because of what you have done, you probably just have a faulty one. However, they are totally justified in voiding your warranty. You upgraded, gotta pay to play.

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post #8 of 12 (permalink) Old 03-10-2010, 11:42 PM Thread Starter
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Quote:
Originally Posted by BlackBaltSS View Post
However, they are totally justified in voiding your warranty. You upgraded, gotta pay to play.
Yeah yeah.... im understanding and aware of that. So both of you guys are recommending a NEW stock OEM radiator... or like/same quality radiator... but im afraid that it will just crack from excess engine mount vibes, or road bumps like the current one that broke.

Are you suggesting that this crack is just a flaw or fluke from the factory then? Cuz heck, if i gotta replace it, why not go all aluminum.... only thing is, is i havent found one yet :(
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post #9 of 12 (permalink) Old 03-11-2010, 09:39 PM Thread Starter
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post #10 of 12 (permalink) Old 03-12-2010, 02:18 PM Thread Starter
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Help MEH bump!

Im putty'd the crack, still looking for a rad vendor... aiming for a solid alum... or even brass endcaps.... i just dont want plastic.
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