Introduction to On Board Diagnostics (II)

Fundamentals of PowertrainControl strategies & OBD IIDiagnosticsHigh Circuit Input: The circuit voltage, frequency or other signal measured at the controlmodule input terminal or Pin is at or near full scale. This is measured with the external circuit,component, or system connected. The signal type (voltage, frequency) shall be included inthe message in place of the word”input”.DTC codes are grouped in different categories. Each category has 100 codes assigned to itas follows: P01 - Fuel and Air metering 100-199, P02 - Fuel and Air metering,P03 - Ignition system or Misfire 300-389, P04 - auxiliary emission controls 400 - 485,and P05 - vehicle speed, idle control, and auxiliary inputs 500 - 574, P06 - Computer andauxiliary outputs 600- 605, and P07 Transmission 700 - 790.Since OBD II focuses on emissions control only DTCs upto P04 followed by three digitfault code are covered here.DTCs are defined to indicate a suspected trouble or problem area and are intendedas a directive to the proper service procedure. DTC s should not be used to indicate theabsence of problems but only to indicate specific fault. The decision to illuminate MIL forany DTC is manufacture specific based on their testing of how each system malfunctionaffects emissions.