Engine Diagnostics & Troubleshooting Trouble Codes
Download the stored codes from the computer by plugging a scan tool into the computer's interface, usually located underneath the driver's side kick panel. Scan tools will vary, but they are typically small held-held devices with a small LCD screen and cable. The software in the scanner will query the vehicle's computer and display the stored trouble codes, which can then be looked up in the repair manual or online for the fault.
Most auto parts stores will scan a car's computer for free, but they cannot "clear" the codes and turn off Check Engine lights in most states. The computer interface will vary, but most use a OBD-I or OBD-2 connector.Manual CodesRotate the ignition switch (key) on and off three times to prompt the computer to flash the Check Engine or SES light, if applicable. Many older vehicles, especially GM models, will flash the SES light a number of times to relate the stored trouble codes. The flashing will stop briefly for each code number Auto diagnostic tools, in sequence, ending with the light going out. This code can then be looked up just like the scanned code.Classic TroubleshootingUse observation to determine the problem with any given engine, as all gasoline motors will use similar designs and break down in common ways.
A gasoline engine requires fuel, spark and air to run Auto tools, and when any of these are reduced or cut off then the motor will not run correctly. A lack of fuel will prevent it from starting or cause it to suddenly stop running. The fuel can be blocked or restricted by a clogged fuel filter or fuel pump fault. An ignition or spark problem can cause a rough running motor or severe lack of power. Restricted air flow can cause a motor to "lope" or lag, and can cause a running engine to stall under load. Bent exhaust piping is an air related problem and can cause the same issues. If these three components of a motor's health are attended to, then most other issues will be minor.
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