Sam Memmolo
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Decoding your warning light! Robert called me and asked me to explain the trouble code dilemma that many of us will face as we drive computer controlled vehicles. He indicated the need for more than just the code number and the plain text explanation of the code.
That air / fuel mixture had to be spark ignited somehow, and then the power generated in the form of heat energy forced the piston down the cylinder on the combustion / power stroke of the conventional 4 cycle engine. This rotated the crankshaft, and off we went. In principal, this is how it was from the late 1800's until about the late 1970's. With stricter environmental legislation, and the need to begin fuel conservation, manufacturers realized that mechanical engine fuel and spark controls were not reliable or durable enough to maintain the 14.7:1 air fuel ratio, dubbed by engineers as Stoichiometric. This 14.7:1 air fuel mixture is critical for proper operation of the catalyst in gasoline fueled engines.
So around 1977 Ford Motor Company introduced the MCU or Microprocessor Control unit. By late 1980, GM and Chrysler followed suit. To keep this in perspective, this was less than 5 years after the introduction of "Electronic Ignition Modules" that replaced the familiar ignition points. While electronic ignition provided a hotter, longer duration ignition spark at the plugs, it also dramatically reduced the need for periodic maintenance. Replacing points every 12 thousand miles or so, became ancient history in a matter of a few years. The early computer systems were basic with very little intelligence, and provided little or no diagnostic functions. In 1981, GM introduced its first fully controlled system with diagnostic trouble codes. This was the "GM CCC" or Computer Command Control system. To alert the operator and the technician to a possible malfunction, a light on the instrument panel would illuminate. The first "DTC's" were now in place. The light initially read "Check Engine". That was confusing, so now many read "Service Engine Soon". This can still be misleading, because the light can illuminate when there is a transmission problem, a suspension or engine problem, and even A/C and heater malfunctions. The trade calls these "MIL" or Malfunction Indicator Lights". Most 1995 and later vehicles are controlled by the second generation computer systems called "OBD-II" or "On-Board Diagnostics II". There are plenty of codes in use now as compared to just a handful in the early systems. OBD-II systems have much greater "Self-diagnostic" ability, and can even track misfires down to the individual cylinders. The point here is to help you get an understanding of what these codes are good for. Just getting a scan tool and retrieving "DTC's" has never fixed a problem. Even if you have a reference manual that explains what the numerical codes means that is simply not enough to fix cars. If it were, we would all be in much better shape. If you experience a MIL illumination, and / or a message in the driver information panel, the first step is to perform a good visual inspection. Step 2 would be to retrieve the trouble code using a scan tool. Once you have the code, and get the definition, you are now ready to "Start" trouble shooting. Let's take this example: you are driving along and everything is normal. Then the dreaded MIL illuminates. Okay, so the oil is fine, the coolant is okay, no belts or hoses broken, and no obvious signs of a major vacuum leak or any other problem. You get the scan tool out and it tells you the code number. You look in the service manual, and the code refers to a defective EGR circuit. Some would think that you could just replace the EGR Valve, and Bingo, the problem is solved. Not so easy! The EGR or exhaust gas recirculation system is comprised of several components. The EGR valve, the vacuum or electric source that supplies the energy to open and close (modulate) the valve, and then the controls that allow the electricity or vacuum to flow to the valve, and some systems even have EGR sensors. Then add to all of the above the circuit in the microprocessor, the wiring and connections, and even the physical plugging up or carboning up of the EGR gas passages, and you have a treat in store for you when it comes to diagnosing the problem. In order to properly diagnose and repair the MIL's illumination, you will also need a diagnostic flow chart. These diagnostic charts take you through a regiment or tests specific to the code. Step by step it directs you through a procedure that should bring you to a diagnosis and pinpoint the problem. Then you can effectively perform the repairs needed. Diagnostic charts will not fix every problem, but they will teach you a tremendous amount about how that particular circuit works, and what the possibilities of component failure are. So, the only way to accurately and professionally diagnose and repair the malfunction, without shot gunning it with expensive components (that cannot be returned to the parts house or the dealer), is to have a decent scan tool with the capability to interface with your particular application, and the appropriate manual with the diagnostic flow charts. You may also need some additional equipment such as a good digital multi meter, a hand operated vacuum pump, and even a heat gun. Robert has located a good manual for the Dodge / Cummins, and that is what you'll need in addition to a scan tool. There are affordable good scanners available from Actron. These are suitable for the do-it-yourselfer, and work well. If you understand the system, follow the charts, and use a little common sense, you should be able to keep things humming yourself, and avoid the costly trips to the dealer. Purchasing these tools, manuals, and electronic devices is not inexpensive, but when a club or a few owners get together and pool their resources, it can easily become manageable. If you opt for an independent repair shop, be sure to question them as to what types of equipment and information systems they have in-house that apply to your vehicle. If they are not able to make you feel warm and fuzzy, be sure to check alternative shops.
The other thing to keep in mind is to either fix the problem or have the problem fixed at the first indication, before the problem manifests into a big deal. I promise you, if you drive it with the light on, you are asking for trouble. Happy Motoring!
Here's how to hear & call Sam
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Let's
take a quick trip back in time before there were electronic power train
management systems. From the automobile's beginning the internal combustion
engine was fueled with a mixture of air and fuel.
With
the advances in microprocessor reliability, and the fact that these marvels were
becoming relatively low cost, auto OEM's decided that using electronics to
control fuel distribution and spark timing would provide more efficient engine
operation over a longer period of time, and thereby lower tailpipe emissions,
and provide better fuel economy, as well as increased performance.
Here are a few more tips.