Chevy Check Engne light on for 20 seconds at start-up

Overheating fuel pump or ignition module?

Check for rodent damage. Do head lights or horn work (no key necessary) ?

If neither the headlights nor the horn are working then the BCM is not functioning. Check BCM fuses (more than one).

First you need to have EBCM - electronic brake control module check for DTC'S - diagnostic trouble code's . If the light is on there is a code stored . I think most part stores can do this and for free . After you find out what code is stored , looking up that code in service repair information for diagnostic trouble shooting chart would be next step . There are a few codes too.
DTC C0035 or C0040
DTC C0045 or C0050
DTC C0110
DTC C0131
DTC C0161
DTC C0186
DTC C0196
DTC C0201
DTC C0240
DTC C0241 or P0856
DTC C0244 or P1689
DTC C0245
DTC C0283
DTC C0287
DTC C0290 or C0292
DTC C0455
DTC C0550
DTC C0558

Find the code do the diagnostic's , fix the problem , wiring issue's , a sensor , bad module ,what ever it is . The light will go out then . Here is a sample of code discription .
• DTC C0035 Left Front Wheel Speed Sensor Circuit
• DTC C0040 Right Front Wheel Speed Sensor Circuit

Yes....10 years or 120,000 miles
Condition
Some customers of 2007-2009 model year Chevrolet Equinox and Pontiac Torrent vehicles equipped with a 3.4L engine (LNJ), and 2008 Chevrolet Express, Silverado; GMC Savana, Sierra vehicles equipped with a 4.3L engine (LU3) may comment about rough engine operation and the illumination of the Check Engine Light. This may be caused by spark plug wire boots that do not provide a sufficiently robust dielectric seal to withstand the high voltage required to fire the spark plugs.
Special Coverage Adjustment
This special coverage covers the condition described above for a period of 10 years or 120,000 miles (193,000 km), whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership. Dealers are to replace all spark plug wires and, if necessary, the spark plug. The repairs will be made at no charge to the customer. For vehicles covered by Vehicle Service Contracts, all eligible claims with repair orders on or after January 5, 2011, are covered by this special coverage and must be submitted using the labor operation codes provided with this bulletin. Claims with repair orders prior to January 5, 2011, must be submitted to the Service Contract provider.
Vehicles Involved
Involved are 2007-2009 model year Chevrolet Equinox and Pontiac Torrent vehicles equipped with a 3.4L engine (LNJ), and 2008 Chevrolet Express, Silverado; GMC Savana, Sierra vehicles equipped with a 4.3L engine (LU3).

The quoted capacity is just under 4 litres including a filter change.

I put 3.5 litres in, start the engine check the oil light goes out after a few seconds, check for leaks from the filter, then switch off engine.

Wait at least 3 minutes, check oil level on dipstick and top up to maximum.

It is the responsibility of the vehicle owner to check the engine oil level periodically (preferably, at least every other fill-up). The oil pressure light does not illuminate until there is practically no oil pressure at all. Most vehicles illuminate the light at somewhere around 7 PSI (49 Kg/cm2). This is low enough to cause severe damage to most modern engines. The engine needs about 20 PSI (1.4 Kg/cm2) to keep the bearings properly lubricated and cooled.

The light is not designed to tell you when you are low on oil. That is what the oil dipstick was created for. These lights are usually only good for letting you know when your engine is is so low on oil that is has most likely already sustained some damage. It is there to let you know to get off of the road IMMEDIATELY.

My question would be this: When was the last time you had an oil change? How long since the oil change did the engine go without the oil level being checked? A new engine will use more oil than one that has 50,000 miles because the piston rings can take that long to get seated in. That car only holds 4 U.S. quarts (3.8 L). On a new 4 cylinder engine, it is not unusual to use 0.5 quarts (0.47 L) every 1000 miles. At that rate, it would only take 7000 miles to get to the point you described (0.6 L left in engine).

Is it your fault? I do not have all the facts with which to make that call. All I can say is look at the information above and you decide.

Folow these steps to make the check engine light disappear:
1. Put the key in and switch it to the ON position, but don't go all the way - the car should not start
2. Wait for three seconds then push the accelerator five times in five seconds or less
3. Remove your foot from the gas and wait for seven seconds
4. Press on the accelerator and keep it pressed for 10 seconds - the SES light will illuminate and start blinking
5. Release your foot from gas
6. Move the key to the Off position and crank up the car.

Take the vehicle to Auto zone to clear the computer. It may just quit doing that after the codes are clear. if the flashing continues the computer is at fault

Catylatic converter. get it checked. Also check to see if your engine ground wire is properly secured.

first if you have a chiltons manual check the troubleshooting /diagnostic codes. Check fuel filter. check the codes for the computer. sounds like the computers sending back a kill engine order.