User manual

18
On-Board Diagnostics (OBD) Diagnostic Service Definitions
4.6.3 Service $03: Emission-related DTCs
The purpose of this service is to enable the scan tool to obtain stored DTCs from the power train
ECMs that are emission-related.
The OBD-I ECM primarily identifies a faulty signal or a faulty sensor using three steps:
• Signal or component shorted to ground
• Signal or component shorted to battery positive
• No signal or component (open circuit)
For each of these tests, a specific trouble code is set.
With OBD-II/EOBD, expanded diagnostics now includes “rationality” testing. One input signal is
compared against other input signals to determine if the reading is reasonable, given the current
operating conditions.
Table 4-3
Diagnostic Trouble Code description
Position Description
1
P = Power train
C = Chassis
B = Body
U = Network
2
0 = Standardized emission-related trouble code
1 = Manufacturer-specific trouble code
2 = Standardized or Manufacturer-specific trouble code
3 = Standardized or Manufacturer-specific trouble code
3
0 = Overall system
1 = Secondary air system/Mixture preparation
2 = Fuel system
3 = Ignition system/Misfires
4 = Additional exhaust gas monitoring
5 = Cruise control/Idle speed control
6 = Input/Output signals, Control units
7 = Gearbox/Transmission
8 = Transmission
9 = Transmission
A = Hybrid Propulsion
B = Reserved
4 & 5 Serial numbering of individual components or systems