Check/Service engine lights

FYI, most computers when they know something is wrong stop running monitors and self test because with something wrong can get false results. Problem with that is that there may be more than one problem with vehicle but only the first problem may be reported and identified because some on board testing may have stopped after first problem occurred.

AFTER REPAIR, CODE(S) NOT CURRENTLY PRESENT. YOUR COMPUTER WILL NOW START PERFORMING SELF TESTING, THAT WAS STOPPED BECAUSE OF PREVIOUS CODE(S)/DTC(s). IF NEW DRIVE CYCLE SELF TEST FINDS NEW PROBLEM AND TURNS ON CHECK ENGINE/SERVICE ENGINE SOON LIGHT, RECOMMEND RETURN FOR NEW DIAGNOSTIC, OR YOU CAN LEAVE VEHICLE (SOMETIMES OVERNIGHT), PAY FUEL AND LABOR COST FOR DIAGNOSTIC TECHNICIAN TO DRIVE FOR SEVERAL DRIVE CYCLES.

This note is to help inform the customer how a automotive OBD (on board diagnostic) computer works with self testing and monitors, some continuous work. Most have to meet ” enabling” condition(s) to run which also means there are like “blocking” condition(s) that will stop monitors/self test from running such as a code set, fuel in tank too high or low, temperature of air/coolant too high, or not run long enough to be considered full drive cycle. Some faults also require more than one failure before they will turn on check/service engine light. A proficient technician with the right scan tool (not just a code reader like many part stores use) can check for “pending codes: which are a failure that has occurred but not enough times to turn on light.

Hope this helps, anymore questions, I am here for you,

Thanks, Jim

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