EOBD Fault Code Prefix

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EOBD Fault Code Prefix

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Diagnostic Code Identifiers (SAE / EOBD Standards)

Here are the explanations of the make up of a diagnostic fault code Prefix:
First (Character)Identifies the Related System
PPowertrain
BBody
CChassis
UNetwork
Second (Digit)Type of Code
0Complies with EOBD Standard
1Manufacturer Specific Enhanced
Third (Digit)Sub-System Affected
0Fuel and air metering and auxiliary emission controls
1Fuel & Air Metering
2Fuel & Air Metering Injector Circuit
3Ignition System or Misfire
4Auxilliary Emission Controls
5Vehicle Speed & Idle Control Systems
6Computer Output Circuit
7Transmission
8Transmission
Fourth & Fifth (Digits)These refer to the specific fault within the sub-system
Note there are also manufacturer-specific codes that are not based on EOBD standards, which are beyond the scope of this guide.
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