Description and Operation

OBD-II Overview

1. Overview. The California Air Resources Board (CARB) introduced On-Board Diagnostic (OBD) regulations for vehicles sold in California starting with the 1988 model year. The first stage, OBD-I, required monitoring of the fuel metering system, exhaust gas recirculation (EGR) system and other emission-related components. The Malfunction Indicator Lamp (MIL) was required to illuminate and warn the driver of a malfunction and the need to service the emission control system. A Diagnostic Trouble Code (DTC) associated with the MIL identified the specific area of the fault. The OBD system, which identifies vehicles exceeding emission standards, was proposed by CARB to improve air quality. The passage of the 1990 Clean Air Act Amendments also prompted the Environmental Protection Agency (EPA) to develop on-board diagnostic requirements. CARB OBD-II regulations were not introduced until 1999, when federal laws took effect. The OBD-II system complies with government standards by monitoring the emission control system. When a system or component exceeds the emission threshold value, or a component operates outside its tolerance, a DTC is stored and the MIL illuminates. The diagnostic executive is a computer program in the engine control module (ECM) or powertrain control module (PCM) that coordinates the OBD-II self-diagnostic system. This program controls all monitors and interactions, DTC and MIL operation, freeze frame data and the scan tool interface. Freeze frame data describes the stored engine conditions, such as engine status, fuel control status, spark, engine speed, load and warm-up status at the moment the first malfunction was detected. Previously stored conditions are replaced only when a fuel or misfire malfunction is detected. This data is accessible with a scan tool to assist in vehicle repair. The core of the OBD-II system is a microprocessor called the engine control module (ECM) or powertrain control module (PCM). The ECM or PCM receives data from sensors and other electronic components (switches, relays, etc.). Based on the received information and the information programmed in its memory (random access memory and others), the ECM or PCM generates output signals to control various relays, solenoids and actuators. 2. Hardware Configuration and Related Terms 1) GST (Generic Scan Tool)

2) MIL (Malfunction Indicator Lamp) - MIL transistor operation

The Malfunction Indicator Lamp (MIL) is connected to the ECM or PCM Malfunction Indicator Lamp terminal and to battery power (open collector driver). On most vehicles the MIL is installed on the instrument panel. The lamp driver cannot be damaged by a short circuit. Lamps with power dissipation much greater than the total MIL and lamp dissipation in the tester may cause a false indication. ? With the ignition on and engine speed (rpm) < MIN. RPM, the MIL illuminates for a visual check by the driver. 3) MIL Illumination When the ECM or PCM detects an emission-related malfunction during the first driving cycle, the DTC and engine data are stored in freeze frame memory. The MIL illuminates only when the ECM or PCM detects the same malfunction associated with the DTC in two consecutive driving cycles. 4) MIL Extinguishing

• Misfire and Fuel System Faults: For misfire or fuel system faults, the MIL may be turned off if the same fault is not detected during monitoring over three subsequent consecutive driving cycles in which conditions are similar to those under which the fault was first detected.
• All Other Faults: For all other faults, the MIL may be turned off after three subsequent consecutive driving cycles during which the monitoring system responsible for illuminating the MIL functions without detecting the fault, and provided no other fault has been detected that could illuminate the MIL independently under the requirements stated above.

5) DTC Erasing. The diagnostic system may erase a DTC if the same malfunction is not recorded again within 40 engine warm-up cycles and the MIL is not illuminated for that DTC. 6) Communication Line (CAN)

• Bus Topology: Line (bus) structure
• Wiring: Twisted pair
• DLC External Cable Length: 5 m max.
• Data Transfer Rate
• Diagnostics: 500 kbps
• Service mode (reprogramming, VIN write): 500 kbps or 1 Mbps

7) Driving Cycle. A driving cycle consists of engine start and engine shutdown. 8) Warm-up Cycle. A warm-up cycle means vehicle operation sufficient to raise the engine coolant temperature by at least 40 °F (22 °C) after engine start, with the temperature reaching a minimum of 60 °F (16 °C). 9) DTC Format

• Diagnostic Trouble Code (SAE J2012)
• DTCs used in OBD-II vehicles begin with a letter followed by a four-digit number.

The first letter of the DTC identifies the controlled system: "P" indicates the powertrain, "C" indicates the chassis, "B" indicates the body, and "U" indicates a network or communication bus code. The first number indicates whether the code is generic (common to all manufacturers) or manufacturer-specific. "0" and "2" mean generic, "1" indicates manufacturer-specific. The second digit, from 1 to 7, indicates the affected system. The list below shows the numbers assigned to each system.

• 1: Fuel and Air Metering
• 2: Fuel and Air Metering (injector circuit malfunction only)
• 3: Ignition System or Misfire
• 4: Auxiliary Emission Controls
• 5: Vehicle Speed Control and Idle Control System
• 6: Computer Output Circuits
• 7: Transmission

The last two digits of the DTC indicate the component or section of the system where the fault is located. 10) Freeze Frame Data. When a freeze frame event is triggered by an emission-related DTC, the ECM or PCM stores various information about the vehicle as it existed at the moment the malfunction occurred. The DTC number together with the engine data can help the technician determine the cause of the fault. Once the 1st driving cycle malfunction data is stored, it remains there even if the malfunction reappears (2nd driving cycle) and the MIL is illuminated.

• Freeze Frame List

1. 1
   Calculated Load Value
2. 2
   Engine Speed
3. 3
   Fuel Trim
4. 4
   Fuel Pressure (if available)
5. 5
   Vehicle Speed (if available)
6. 6
   Engine Coolant Temperature
7. 7
   Intake Manifold Pressure (if available)
8. 8
   Closed Loop or Open Loop Operation
9. 9
   Malfunction Code

3. OBD-II Readiness Check [Hyundai Motors Drive Cycle]. The Hyundai OBDII Drive Cycle is designed to perform and complete OBDII monitoring. To complete a specific monitor for repair verification, follow the driving cycle table below. The Hyundai OBDII drive cycle consists of two modes (Mode 1 and Mode 2), and Mode 2 is used to perform catalyst diagnosis on Delphi ECM only.

• Continental, Bosch or Kefico EMS: One Mode 1 driving cycle must be performed to diagnose all systems.
• Drive cycle for Mode 2 should be performed twice in a row. The series after Mode 1 is performed once for diagnosis on all systems.
• Mode 1

  

• Mode 2

  

Mode	No	Operation	Speed (mph)	Duration (s)	E/Time (s)	Notes
Mode 1	1	Starting the Engine	0	0	0	ECT @ Start 32~104°F
	2	Idle (N)	0	30	30	Neutral range
	3	Idle (D)	0	270	300	D Range
	4	Acceleration	0 > 50	15	315
	5	Steady speed	50	230	545
	6	Deceleration	50 > 45	5	550
	7	Steady speed	45	5	555
	8	Acceleration	45 > 55	5	560
	9	Steady speed	55	5	565
	10	Deceleration	55 > 45	5	570
	11	Steady speed	45	5	575
	12	Repeat steps 8 through 11 ten times.	-	180	755
	13	Acceleration	45 > 55	5	760
	14	Steady speed	55	5	765
	15	Deceleration	55 > 0	45	810
	16	Idle (D)	0	120	930	D Range
	17	Idle (N)	0	760	1690	Neutral range
	18	Acceleration	0 > 55	15	1705
	19	Steady speed	55	60	1765
	20	Deceleration	55 > 0	15	1780
	21	Idle (D)	0	60	1840	D Range
	22	Acceleration	0 > 55	15	1855
	23	Steady speed	55	60	1915
	24	Deceleration	55 > 0	15	1930
	25	Idle (D)	0	60	1990	D Range
	26	Acceleration	0 > 40	15	2005
	27	Steady speed	40	15	2020
	28	Acceleration	40 > 50	15	2035
	29	Steady speed	50	5	2040
	30	Deceleration	50 > 40	15	2055
	31	Steady speed	40	60	2115
	32	Repeat steps 28 through 31 five times.	-	380	2495
	33	Acceleration	40 > 50	15	2510
	34	Steady speed	50	5	2515
Mode 1	35	Deceleration	50 > 0	40	2555
	36	Idle (D)	0	25	2580	D Range
Mode 2	1	Starting the Engine	0	0	0
	2	Idle (N)	0	30	30	Neutral range
	3	Idle (D)	0	210	240	D Range
	4	Acceleration	0 > 49	16	256
	5	Deceleration	49 > 47	2	258	Lift foot off pedal: APS = 0
	6	Steady speed	47	10	268
	7	Acceleration	47 > 55	4	272	Medium tip or wide-open throttle acceleration
	8	Deceleration	55 > 52	3	275	Lift foot off pedal: APS = 0
	9	Steady speed	52	10	285
	10	Deceleration	52 > 45	3	288	Lift foot off pedal: APS = 0
	11	Acceleration	45 > 47	2	290
	12	Repeat steps 6 through 11 twelve times.	-	330	620
	13	Steady speed	47	57	677
	14	Deceleration	47 > 0	8	685
	15	Idle (D)	0	60	745	D Range
	16	Acceleration	0 > 50	15	760
	17	Steady speed	50	90	850
	18	Deceleration	50 > 0	10	860
	19	Repeat steps 15 through 18 twice.	-	175	1035
	20	Idle (D)	0	90	1125	D Range

1) Catalyst Monitor. The catalyst monitor is a self-test strategy within the ECM or PCM that uses the downstream heated oxygen sensor (HO2S) to determine when the catalytic converter has deteriorated below the minimum efficiency level required to control exhaust emissions. 2) Misfire Monitor. A misfire is defined as the lack of proper combustion in the cylinder due to a lack of spark, poor fuel metering, or poor compression. Any combustion that occurs outside the cylinder or at the wrong time is also a misfire. The misfire detection monitor detects fuel, ignition, or mechanical misfires. The purpose is to protect the catalytic converter from irreversible damage and to alert the customer to an emissions failure or a service-required condition by illuminating the MIL. When a misfire is detected, special software saves so-called freeze frame data. Freeze frame data records the vehicle operating conditions at the time the misfire detection monitor strategy detected the fault. 3) Fuel System Monitor. The fuel system monitor is a self-test strategy within the ECM or PCM that monitors the adaptive fuel table. The system uses the adaptive fuel table to compensate for normal variation in fuel system components due to wear or aging. During normal vehicle operation, if the fuel system runs lean or rich, the adaptive value table shifts the fuel delivery calculations to remove the bias. 4) Engine Cooling System Monitor. The cooling system monitor is a self-test strategy within the ECM or PCM that monitors the ECT (engine coolant temperature) sensor and the thermostat for circuit continuity, range/performance, and rationality faults. 5) Oxygen Sensor Monitor. OBD-II regulations require monitoring of the oxygen sensor (HO2S) to detect sensor deterioration that exceeds threshold values. The downstream oxygen sensor is located downstream of the Warm-Up Three-Way Catalytic Converter (WU-TWC) to determine catalyst efficiency. Although the downstream HO2S is similar in type to the one used for fuel control, it operates differently. The downstream HO2S is monitored to determine whether voltage is being generated. This voltage is compared with a calibrated acceptable range. 6) Evaporative Emission (EVAP) System Monitor. The EVAP monitor is a self-test strategy within the ECM or PCM that checks the integrity of the EVAP system. The complete evaporative system detects leaks, or combined leaks, equal to or greater than a leak caused by a 0.040 inch and a 0.020 inch orifice. 7) Air Conditioning (A/C) System Monitor. The A/C system monitor is a self-test strategy within the ECM or PCM that monitors the A/C system for faults in all A/C system components. N/A. 8) Comprehensive Component Monitor. The comprehensive component monitor is a self-test strategy within the ECM or PCM that detects a fault in any electronic component or transmission system that provides input to the ECM or PCM and is not exclusively an input for any other OBD-II monitor. 9) A/C Component Monitor. Requirement: If the vehicle includes an engine control strategy that disables fuel and/or spark control at idle when the A/C system is on, the OBD II system must monitor all electronic A/C system components for faults that prevent the system from causing the alternate control when the A/C system is on, or that cause the system to cause the alternate control when the A/C system is off. In addition, the OBD II system must monitor for faults all electronic A/C system components that are used as part of the diagnostic strategy for any other monitored system or component. Implementation plan: No engine control strategy is included that changes the idle fuel and/or spark control position when the A/C system is on. A/C system component faults are not used as part of the diagnostic strategy for any other monitored system or component.