On Board Diagnostics II

1. On Board Diagnostics II What is OBD II? What is its purpose? Active and passive tests Monitors DTC’s Generic OBD II data

2. OBD II On board diagnostics originated in 1980’s OBD I mandated for vehicles sold in Calif. in 1988 MIL to alert driver of malfunction Ability to record and transmit DTC’s Monitored sensors for opens and shorts OBD I did not monitor: Catalyst efficiency EVAP system leaks Catalyst damaging events such as misfires OBD I did not protect catalyst from damage by incorrect fueling or misfire

3. What is OBD II Federal regulations for automobiles produced for sale in 1996 Some manufacturers began to phase in OBD II as early as 1994 Established federal test procedure for exhaust emissions and required on-board monitoring of emission control systems for correct operation and efficiency

4. Purpose Designed to detect vehicle problems that can cause increased emissions Alerts driver of emission related problems Standardization: DTC’s Scan tool interface MIL operation DLC shape and location DLC now provides power and ground for scan tool Performs active and passive tests on emission systems

5. Tests Active tests PCM changes something and measures response Passive tests Watches components during normal operation, but does not take active role in test process

6. Monitors Tests performed by diagnostic system to check performance of various components and subsystems If a component or system failure is detected that can increase emissions, MIL is illuminated and DTC will set Continuous: any component or subsystem that has catalyst damaging potential Non-continuous: performs once per trip; once monitor runs to completion it does not run again until next drive cycle Trip: a key cycle (Key-On, start-to-run, Key-Off) where driving conditions enable a monitor to run

7. Continuous Monitors Comprehensive Component Monitor (CCM): tests inputs and outputs Functionality: tests for opens, shorts and grounds Rationality: tests for inaccurate signals Some components are tested when key is turned on Some components are tested when engine meets necessary operating conditions

8. Throttle Position Sensor

9. Continuous Monitors Misfire Monitor Constantly monitors engine for misfire Determines classification of misfire Misfire type A: within 200 rpms Catalyst damaging Logs DTC and flashes MIL Misfire type B: within 1000 rpms Increases emissions Logs DTC and illuminates MIL

10. Continuous Monitors Fuel Monitor Monitors long and short term fuel correction LTFT STFT Illuminates MIL and stores DTC when corrections exceed preprogrammed limits for extended periods

11. Noncontinuous Monitors Oxygen Sensor Monitor: checks O2S voltage ranges and response times Catalyst Monitor: usually uses downstream O2S to check catalyst efficiency Looks for low activity on downstream O2S compared to upstream O2S’s EGR Monitor: checks for EGR flow

12. Noncontinuous Monitors EVAP Monitor: Non-enhanced: monitors effects of purge vapor on engine fuel control Enhanced: monitors effects of purge; also checks system for leaks AIR Monitor: checks components and operation of secondary air injection system Thermostat Monitor: (2000) monitors time to warm-up PCV Monitor: (2002) monitors integrity of closed crankcase ventilation system

13. DTC’s OBD I codes: Lack of information; vague definitions Code retrieval process varied by manufacturer Code identification set by manufacturer No consistency- too many variables Made vehicles difficult to diagnose and repair

14. DTC’s OBD II codes: A codes: sets DTC and illuminates MIL on first trip failure (misfire) B codes: sets DTC and illuminates MIL on second consecutive trip failure C and D codes: non-emission related; normally will not illuminate MIL, but may illuminate a warning lamp

15. DTC’s OBD II codes: Codes are retrieved and erased with scan tool only Code set parameters are clearly defined Standardized alphanumeric DTC identification Freeze frame data: Data stored with DTC about operating conditions when DTC is set RPM; VSS; CTS; Engine Load; MAP or MAF; Fuel Status; LTFT/STFT

16. DTC’s Pending codes: One-trip failure for a two-trip DTC Sets in memory and stores freeze frame data but will not illuminate MIL Second consecutive failure- matures into DTC and illuminates MIL DTC and MIL erasure : Requires 3 consecutive good trips to turn off MIL Requires 40 warm-up cycles to erase DTC

17. DTC’s The OBD-II System DTC Priority is listed below. Priority 0—Non-emission-related codes Priority 1—One-trip failure of two-trip fault for non-fuel, non-misfire codes Priority 2—One-trip failure of two-trip fault for fuel or misfire codes Priority 3—Two-trip failure or matured fault of non-fuel, non-misfire codes Priority 4—Two-trip failure or matured fault for fuel or misfire codes

18. DTC Numbering First digit: P: powertrain B: body system C: chassis system U: network communication Second digit: 0: SAE defined (standardized list that applies to every vehicle regardless of manufacturer) 1: manufacturer specific 2: to be used once manufacturer has filled all “1” code designations

19. DTC Numbering Third digit: Assigned to subsystem affected 1: air/fuel control 2: fuel system (injectors) 3: ignition system/ misfire 4: auxiliary emission controls (EGR/EVAP/AIR/Cat) 5: auxiliary inputs: vehicle speed/ idle speed control 6: computer system (PCM or communications) 7: transaxle/transmission 8: transaxle/transmission

20. DTC Numbering Fourth and fifth digits: Paired numbers Indicate exact nature of fault that stored DTC Correspond to old OBD I codes Example: P0300 Example: P0304 Example: P0440

21. Generic OBD II Displayed data available on all OBD II vehicles using a generic scan tool Mode 1: powertrain data (PID) Mode 2: freeze frame data Mode 3: DTC’s Mode 4: clear DTC’s; readiness status for noncontinuous monitors Mode 5: O2S test results Mode 6: test results for noncontinuous monitors Mode 7: test results for continuous monitors Mode 8: bidirectional control of onboard systems Mode 9: module identification

22. Freeze-frame items include: Calculated load value Engine speed (RPM) Short-term and long-term fuel trim percent Fuel system pressure (on some vehicles) Vehicle speed (MPH) Engine coolant temperature Intake manifold pressure Closed/open-loop status Fault code that triggered the freeze-frame If a misfire code is set, identify which cylinder is misfiring

23. Terms to know Monitors: test performed by diagnostic system Enabling criteria: exact conditions needed before a test can run (provided by a “trip”) Active test: test strategy used by PCM that changes some aspect of system operation and monitors effects of that change Passive test: test that watches components during normal operation but does not take any role in testing process KOEO: Key-On-Engine-Off KOER: Key-On-Engine-Running PID: parameter identification- individual items in scan tool data display Rationality: compares sensor inputs to see if they make sense Readiness Status: list of monitors displayed on scan tool telling whether various monitors have run to completion- does not tell of pass or failure only completion Warm-up cycle: start-to-run where coolant temp starts below and rises above 160 degrees F, and increases by at least 40 degrees F