Engine light diagnosis
Basic check engine light diagnosis tips. Determining which part or area of a computerized engine control system is defective requires having a thorough knowledge of how the system operates. Then you can follow a logical troubleshooting procedure until the malfunction is uncovered. Most late-model computerized engine control systems have self diagnostic capabilities.
Stored codes can be retrieved with an inexpensive auto scan tool. This will help isolate the specific systems that contain the failure and greatly reduce the amount of troubleshooting time required. A good car repair manual will not only provide you with repair diagrams and diagnostic charts but also provides an education of the system that has the defect. When you fully understand the operation of the circuit in question the malfunction often jumps out at you.
Basic troubleshooting tests
The following methods can be used to check individual system components and I personally always start with a visual inspection. In many cases this first step will direct you right to the particular problem. When performing visual inspections for check engine light diagnosis look for obvious problems. Any part that is burned, broken, cracked, corroded, or has any other visible problem must be replaced or repaired before continuing with the diagnosis. Examples of things you may find on a visual inspection include a disconnected sensor. Or maybe even a broken or disconnected vacuum line, and also wiring that has been damaged from an external source. Many times I will find damaged wiring or components from external sources such as mice or rodents. They love to chew on these tasty auto parts. Also, when I lived up north. It was common to find damage from ice balls and fender burgs. Also corrosion problems caused by salted roads.
Basic electrical diagnosis
I always recommend having a automotive meter to perform quick resistance and voltage checks. Most sensors and output devices can be checked with an ohmmeter. For example, an ohmmeter can be used to check a temperature sensors operation. Normally the ohmmeter reading is low on a cold engine and high or infinity on a hot engine. If the engine coolant sensor is a positive temperature coefficient or PTC. If the sensor were a negative temperature coefficient or NPC, the opposite readings would be expected on the meter. Output devices such as coils or motors can also be checked with an ohmmeter. Resistance readings can be compared to specifications listed in your auto repair manuals. You can also use the same multimeter to perform voltage checks on sensors. You can compare voltage readings from many sensors, output devices, and their wiring can be diagnosed by checking the voltage to them. And also in some cases, the voltage that is going away from the sensor. Even oxygen sensors can be checked in this manner if the scale chosen on the meter is in mili volts.
By watching their activity you are doing more than just testing them. Often problems elsewhere in the system cause this device to behave abnormally. With a little practice, a do-it-yourself auto mechanic will be able to pick up these abnormal activities and relate them to the systems that affect these readings. Service bulletin informationWhen it comes to engine light diagnosis, technical service bulletins are extremely helpful. If a mechanic does not look for an issued service bulletin many hours of troubleshooting time may be wasted. This information is available from different suppliers, and also in the recommended car repair manual available through this website. I have also taken some of the most popular technical service bulletins and made them available on the page labeled
auto repair news
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