GM Service Manual Online
For 1990-2009 cars only

When you've started your engine, let it run for 20 to 30 seconds before you put a load on the engine. But don't leave the vehicle while the engine is running.

Avoid unnecessary idling of diesel engine equipped vehicles.

If the engine idles too long, the temperature of the engine coolant will fall below the normal operating range. Low engine operating temperature causes several conditions which affect engine operation and reduce engine life.

The engine should be permitted to go through a warm-up period. Operate the vehicle at a minimum of 600 rpm during the warm-up period. During this period and during operation, the following observations should be made.

During this warm-up period, check your warning lights and gages:

    • If oil pressure doesn't begin to rise within 15 seconds of starting, stop the engine and find the cause.
    • If the engine coolant temperature gage needle goes into the hot area on the gage, stop the engine and find the cause of the overheating.
    • If you have air brakes, the dual-needle air pressure gage should read at least 115 psi (790 kPa) for both service systems before you try to move the vehicle. When air pressure is below 60 psi (420 kPa), the LOW AIR light will come on and you will hear a tone alarm. If the pressure doesn't build up or drops during warm-up, stop the engine and find the cause before you try to move the vehicle. Recommended air pressure before actually driving away is 120 psi (830 kPa).
    • The charging system light should come on when the ignition key is turned to RUN or START and should go out when the engine is running above idle. If the light doesn't go out or comes back on during normal engine operation, have the charging system checked right away. (This light tells you if the generator is not charging; it doesn't reflect the condition of the battery.)
    • The voltmeter charge indicator gage tells you the condition of your battery's charge. The gage should be in the center area during engine operation. The red area on the left indicates an undercharge condition; the red area on the right indicates an overcharge. If the gage is in either red area, have the battery and charging system checked right away.

Notice: Do not allow the engine to operate at low idle for more than five minutes. This can cause low engine operating temperatures which can affect engine operation and reduce engine life. Engine idle speed should be increased to 1200 rpm whenever extended idle is required. Once started, the engine should be placed under load to allow the engine coolant temperature to reach 150°F (66°C) before shutting off the engine.