About a week ago while on the interstate I got a check engine light with misfiring and severely reduced engine power. At the time I was low on fuel with about 48 miles until empty and up until this point the car has run flawlessly. I was NOT out of fuel. However, earlier in the week my fiance got half a tank of premium gas from a non-mainstream station. I wondered if I had "bad gas" perhaps with water in it from that questionable station. I AAA guy stopped and gave me 2 gallons of gas. With some initial misfiring and rough idle the car started and then drove fine. I then drove 6 miles to my usual station and filled the tank with premium. I drove home and checked my codes. The only relevant code was PCM P0300 H engine misfire detected. The problem had resolved. I cleared all codes and the engine light went away. As I drove the car during the week I occasionally chjecked the codes. There was no recurrences of the code or the problem. Until today. With about a 1/4 - 1/3 of a tank the check engine light came on. The car was running fine. Todays code was PCM P0442 H C -- indicating a current problem. I have not been able to find a definition for this code yet. I again filled the tank with 93 Chevron and cleared the code. It has not returned in the last few engine cycles and the check engine light has stayed off. I think this problem is fuel related. If it is a little water in the tank is there an easy way to deal with this problem? What other things could be responsible? And why can I not find the P0442 code listed?


[Modified by Alesnik-MD, 7:38 PM 5/24/2003]

 

P0442 is a failure of the small leak test of the EVAP (fuel evaporative emission system). The PCM uses engine vacumn to occasionally test the EVAP system by creating a vacumn in the system and then sealing and watching system pressure. P0440 means a large leak, P0442 is a small leak. Check that you've got the fuel filler cap on correctly as this can often lead to a failure of this test.

Steve


[Modified by BlackZ06, 4:43 PM 5/24/2003]

 

Thanks Stephen.

But Why would it code 8 days and 240 miles after I last filled up? What other small leaks are we talking about?

 

The test isn't run continuously. Certain conditions must be present for the test. For example, the fuel level must be between 20 and 85 percent full, the engine must have performed a "cold" start (the Engine coolant temp at start must not be more than 14 degrees F higher than the Intake air temp), the vehicle speed is below 75 mph, and barometric pressure is "normal".

In other words the test is performed once per "cold start" drive cycle, and if your fuel tank is full, or close to full, then it won't perform the test either.

When the test fails, the DTC is stored and the CHECK ENGINE light is illuminated. If you do nothing to erase the code, but let's say for the sake of argument that you add fuel shortly after the failure and it was the gas cap that caused it, the DTC will clear after three straight succesful tests, and the CHECK ENGINE light will go out.

Diagnostis listed are:
l* inspect for loose, incorrect, damaged or missing fuel fill cap
* inspect EVAP canister service port dust cap and/or schrader valve
* Inspect for damaged EVAP canister purge valve
- Raise vehicle and
* Inspect for disconnected or damaged EVAP pipes and hoses.
* Inspect for damaged EVAP canister vent valve

Check the fuel filler cap (be sure it is seating OK) and clear the code. If it comes back, it is probably easiest to let the dealer hunt this one down.

Steve :cheers:


[Modified by BlackZ06, 6:35 PM 5/24/2003]


[Modified by BlackZ06, 6:46 PM 5/24/2003]

 

Thank you very much, Steve. How did you know all that stuff?

 

Because I'm f**king brilliant :lol: :lol: :lol: ????

Actually, the truth is I have a set of the service manuals for my 2001 vehicle, and it is kinda fun, in a perverse way, to look up the codes and learn more about how the car works.

If you do any work on the car yourself (I've replaced brake rotors, for instance) they are really invaluable. You can order them through your dealer, or get them direct from Helm, who publish them for GM.

Take a look at:
http://www.helminc.com/

and you can order them there alos.

Have a good holiday weekend,

Steve :D


[Modified by BlackZ06, 7:13 PM 5/24/2003]

 

Here's a brief explanation of your problem

Document ID# 824194
1999 Chevrolet/Geo Corvette

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Info - Evaporative Emissions DTC P0440, P0441, P0442, P0446 #00-06-04-011A - (10/04/2001)
Evaporative Emissions DTC P0440, P0441, P0442, P0446
1996-2002 Passenger Cars and Trucks

With Enhanced Evaporative Emissions Engines

Except 1998-1999 Chevrolet Prizm

This bulletin is being revised to add model years and diagnostic enhancements. Please discard Corporate Bulletin Number 00-06-04-011 (Section 6-Engine).

Enhanced Evaporative Emissions testing of 1996 and newer vehicles with enhanced evaporative emissions requires more stringent testing of the fuel system for evaporative emissions leaks. Vehicles with this system use an on-board diagnostic module (i.e. Powertrain Control Module (PCM) or Vehicle Control Module (VCM) as the controller. For the balance of this bulletin, we will refer to either of these components as a module.

Enhanced Evaporative Emission tests may be performed by the vehicle's module when specific conditions are met. These conditions are determined by the calibration within the module. These calibrations are vehicle platform and engine family specific.

When the key is turned to the start or run position, the module checks the output of various sensors on the vehicle to determine when and if the Evaporative Emissions tests should be run. Refer to Engine Controls sub-section of the appropriate Service Manual for specific DTC information.

Some of the most widely used parameters are listed below:

The Barometric Pressure (BARO) is greater than a specified kPa (psi).
The system voltage is between 10 and 18 volts.
The intake air temperature (IAT) is within specified temperature values.
The engine coolant temperature (ECT) is within specified temperature values.
The ECT and IAT are within specified temperatures of each other when the vehicle engine was started.
The fuel level sensor indicates the fuel level is greater than a specified % of empty and less than a specified % of full. (For a 76 L (20 gal) fuel tank, a fuel level of more than 11 L (3 gal) but less than 64 L (17 gal) or as specified in the calibration).
Some platforms such as the Alero and Grand Am, use a miles driven check as well.
For the ECT and IAT to be within the specified temperatures of each other at the time of engine start-up, the engine will have to be in the non-running condition for a long enough period of time for the engine coolant temperature to drop from its normal operating temperature down to roughly 30°C (90°F). This could take several hours.

When the control module determines that the above conditions are met, the module tests for a leak in the EVAP system by:

Electrically closing the vent valve in order to seal the system.
Electrically opening the purge valve which allows the running engine to draw a vacuum on the fuel tank.
The module then closes the purge valve, resealing the system.
The module then monitors the fuel tank pressure sensor and determines:
If vacuum was achieved.
If a leak is present, how large the leak is.
If vacuum was not achieved.
If one of the above tests fails, the module remembers that the system failed the test.
If the module sees a failure of the EVAP test for two consecutive tests, the module will set a trouble code for EVAP leak (DTCs P0440, P0442, or P0446).

Important
If the PCM is completing the EVAP diagnostic, filling of the fuel tank cannot be completed as the vent valve will be closed and the fuel dispenser nozzle will sense the pressure build-up and shut down. This is the expected result. No parts should be replaced as nothing is faulty. To keep from encountering this situation, it is imperative all customers and dealership personnel be advised NOT TO FILL THE FUEL TANK WITH THE ENGINE RUNNING. If the condition is encountered, turn the ignition to the OFF position for a minute. This will allow the PCM to go to sleep completely, thereby opening the vent valve.




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.
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© Copyright General Motors Corporation. All Rights Reserved.


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Document ID# 824194
1999 Chevrolet/Geo Corvette

 

Thanks for the info, Tom.