From Joe Heuel's Desk






Check Engine light Repairs


Today’s cars are outfitted with a system called OBD, which stands for Onboard Diagnostic System. For decades, cars had dashboard indicators that only monitored the basics: fuel level, oil temperature, coolant temperature and whether our generators or alternators were charging. That all changed in 1981 when federal clean air statutes required catalytic converters on all domestic cars and light trucks to help reduce the level of smog-causing emissions in the atmosphere. 

In April 1985, the California Air Resources Board (CARB) approved On-Board Diagnostic system regulations, referred to as OBD. These regulations, which apply to almost all 1988 and newer cars sold in the State of California, require that the engine control module (ECM) monitor critical emission related components for proper operation and illuminate a malfunction indicator lamp (MIL) on the instrument panel when a malfunction is detected. 

In 1996, the federal government required U.S. automakers to upgrade to OBD II, a sophisticated system of sensors and actuators that conduct on-the-road diagnostic tests. When the OBD II detects a problem, it logs it as a trouble code in its computer memory. Once retrieved via a diagnostic reader, this code directs the repair technician to the source of the trouble.

However this System gives the technician only a general description of the Problem, for example, Mixture adaptation at Limit, that means that the Fuel mixture is either too rich or too lean, however there are many possible reasons for that, for example, the Car’s intake manifold gasket is defective and lets extra air get into the Engine, the Air Mass Meter may be defective and misreading the amount of Air going into the Engine, the oxygen Sensor is defective and reads rich or too lean,  the Engine temperature Sensor is defective and reads Engine cold all the Time so your ECU keeps enriching the Fuel Mixture which is needed for a cold Engine. There are many many more possibilities for just this one Malfunction Code and there are hundreds of different Malfunction Codes so you can see that this type of Repair is highly complicated. There is a widely spread misconception, that all “today’s mechanics” have to do is plug into a Computer and that Computer will tell them what Part to replace. Nothing could be further from the truth, cars are more complicated than ever, and mechanics are now called Technicians that need among other things, extensive knowledge in electronics, the OBD system like any other system is able to malfunction, giving false alarms via check engine Light or leading the technician down the wrong path.

You may have seen on TV or read in some Publications, all you need to do is buy a Code-Reader and you can Repair your Vehicle yourself. It is also a gross misstatement and shows how misinformed the Media is on this Issue. There is the fact that these simple Code Readers also called “generic Code Readers” are not capable of accessing large portions of the Cars electronics due to the fact that most manufacture’s have their own special software to access each Control unit like the Engine ECU separately. These manufacturers’ specific readers are mostly in specially designed Laptops and sometimes exceeded $30k. You can see how today’s repair facility’s need to spend large amounts of money to keep up with the advancement of Car Manufacturers.

All these factors must be considered when encountering a check engine light repair, it will take a skilled and well trained technician and sometimes a substantial amount of time to run multiple component tests especially when encountering an intermittent problem where components test OK one moment and fail when retested.

So please show patience when you Car is in the Shop for a check engine light repair, a shop that calls you after an hour with its diagnosis may not do the necessary component testing that will save you from spending money on unnecessary repairs. Time now is money saved later.


By Joe Heuel