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On Board Diagnostic II trouble code break-down
With the use of a generic scan tool, specific failure codes can be retrieved that provide more detailed information as to the nature of an electrical failure than the key dance method.
OBDII systems have the ability to test, store, and display failures in the body, chassic, powertrain, or network or data link code systems. These codes are referred to as DTC's or Diagnostic Trouble Codes.
A trouble code is displayed similar to this P0753.
The letter indicates that the failure is in the powertrain system.
The first digit indicates who assigned the code. 0 would mean that it is a federally mandated code. A 1 would mean its an individual vehicle
manufacturer code.
The second number indicates the specific system of malfunction.
0 means it's the entire system
1,2 means it's air or fuel
3 means ignition
4 means auxillary emission controls
5 means speed or idle controls
6 means PCM system
7 means transaxle/transmission
8 means non-computer controlled powertrain
The last two digits indicate specific malfunction circuit.
The retrieval of specific P code failures can be very beneficial in diagnosing a check engine light condition on an OBDII vehicle. While the key dance method can be helpful in pointing to which system is having a problem, it will not pin-point the type of failure nor the specific component in that area experiencing difficulty. A prime example of this is the key dance code 21. It corresponds to an o2 sensor related failure. For which there are at least 23 different types of failures. The problem could be in the upstream o2, the downstream o2, the wiring, or the pcm.
Doug
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