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CHAPTER 19 Onboard Diagnosis

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CHAPTER 19

Onboard Diagnosis

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.2

After studying Chapter 19, the reader will be able to:

1. Prepare for ASE Electrical/Electronic Systems (A6) certification test content area “A” (General Electrical/Electronic Systems Diagnosis).

2. Explain the purpose and function of onboard diagnosis.

3. List the various duties of the diagnostic executive (task master).

4. List five continuous monitors.

5. List five noncontinuous monitors.

OBJECTIVES

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.3

KEY TERMS

• California Air Resources Board (CARB)

• Component identification (CID)

• Comprehensive component monitor (CCM)

• Diagnostic executive • Enable criteria • Exponentially weighted

moving average (EWMA) monitor

• Federal Test Procedure (FTP)

• Freeze-frame

• Functionality • Malfunction indicator lamp

(MIL) • On-board diagnosis (OBD)• Parameter identification

(PID) • Rationality • Society of Automotive

Engineers (SAE) • Test identification (TID) • Task manager

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.4

ON-BOARD DIAGNOSTICS GENERATION-II (OBD-II) SYSTEMS

• PURPOSE AND FUNCTION OF OBD II• The automotive industry calls these systems On-

Board Diagnostics (OBDs). The California Air Resources Board (CARB) developed the first regulation requiring manufacturers selling vehicles in that state to install OBD.

• OBD Generation I (OBD I) applies to all vehicles sold in California beginning with the 1988 model year.

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.5

ON-BOARD DIAGNOSTICS GENERATION-II (OBD-II) SYSTEMS

FIGURE 19–1 A typical malfunction indicator lamp (MIL) often labeled “check engine.”

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.6

ON-BOARD DIAGNOSTICS GENERATION-II (OBD-II) SYSTEMS

• OBD-II OBJECTIVES• Generally, the CARB defines an OBD-II-equipped

vehicle by its ability to do the following:• 1. Detect component degradation or a faulty

emissionrelated system that prevents compliance with federal emission standards.

• 2. Alert the driver of needed emission-related repair or maintenance.

• 3. Use standardized DTCs and accept a generic scan tool.

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.7

DIAGNOSTIC EXECUTIVE AND TASK MANAGER

• On OBD-II systems, the PCM incorporates a special segment of software.

• On Ford and GM systems, this software is called the diagnostic executive.

• On Chrysler systems, it is called the task manager.

• This software program is designed to manage the operation of all OBD-II monitors by controlling the sequence of steps necessary to execute the diagnostic tests and monitors.

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.8

MONITORS

• A monitor is an organized method of testing a specific part of the system.

• Monitors are simply tests that the computer performs to evaluate components and systems.

• If a component or system failure is detected while a monitor is running, a DTC will be stored and the MIL illuminated by the second trip.

• The two types of monitors are:• CONTINUOUS MONITORS• NONCONTINUOUS MONITORS

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.9

OBD-II MONITOR INFORMATIONCOMPREHENSIVE COMPONENT MONITOR

• The circuits and components covered by the comprehensive component monitor (CCM) do not include those directly monitored by another monitor.

• However, OBD II also requires that inputs from powertrain components to the PCM be tested for rationality, and that outputs to powertrain components from the PCM be tested for functionality.

• Both inputs and outputs are to be checked electrically.

• Rationality checks refer to a PCM comparison of input value to values.

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.10

OBD-II MONITOR INFORMATION

• CONTINUOUS RUNNING MONITORS• ONCE PER TRIP MONITORS• EXPONENTIALLY WEIGHTED MOVING

AVERAGE (EWMA) MONITORS• NONCONTINUOUS MONITORS

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.11

ENABLING CRITERIA

• With so many different tests (monitors) to run, the PCM needs an internal director to keep track of when each monitor should run.

• As mentioned, different manufacturers have different names for this director, such as the diagnostic executive or the task manager.

• Each monitor has enabling criteria. • These criteria are a set of conditions that must be

met before the task manager will give the go-ahead for each monitor to run.

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.12

ENABLING CRITERIA

• Most enabling criteria follow simple logic, for example:• The task manager will not authorize the start of the

O2S monitor until the engine has reached operating temperature and the system has entered closed loop.

• The task manager will not authorize the start of the EGR monitor when the engine is at idle, because the EGR is always closed at this time.

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.13

ENABLING CRITERIA

• TRIP• WARM-UP CYCLE• MIL CONDITION: OFF• MIL CONDITION: ON STEADY• MIL CONDITION: FLASHING• MIL: OFF

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.14

OBD-II DTC NUMBERING DESIGNATION

• A scan tool is required to retrieve DTCs from an OBD-II vehicle.

• Every OBD-II scan tool will be able to read all generic Society of Automotive Engineers (SAE) DTCs from any vehicle.

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.15

OBD-II DTC NUMBERING DESIGNATION

FIGURE 19–2 OBD-II DTC identification format.

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.16

OBD-II DTC NUMBERING DESIGNATION

• DTC NUMBERING EXPLANATION• TYPES OF DTCS

• TYPE A CODES• TYPE B CODES• TYPE C AND D CODES

• DIAGNOSTIC TROUBLE CODE PRIORITY

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.17

OBD-II FREEZE-FRAME

• To assist the service technician, OBD II requires the computer to take a “snapshot” or freeze-frame of all data at the instant an emission-related DTC is set.

• A scan tool is required to retrieve this data.

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.18

OBD-II FREEZE-FRAME

• 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

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.19

OBD-II FREEZE-FRAME

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.20

What Are Pending Codes?

• Pending codes are set when operating conditions are met and the component or circuit is not within the normal range, yet the conditions have not yet been met to set a DTC. For example, a sensor may require two consecutive faults before a DTC is set. If a scan tool displays a pending code or a failure, a driveability concern could also be present. The pending code can help the technician to determine the root cause before the customer complains of a check engine light indication.

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.21

ENABLING CONDITIONS OR CRITERIA

• These are the exact engine operating conditions required for a diagnostic monitor to run.• Example:

• Specific RPM• Specific ECT, MAP, run time, VSS, etc.

• PENDING• CONFLICT• SUSPEND

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.22

PCM TESTS

• RATIONALITY TEST• FUNCTIONALITY TEST• ELECTRICAL TEST

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.23

GLOBAL OBD-II

• All OBD-II vehicles must be able to display data on a global (also called generic) scan tool under nine different modes of operation.

• The global (generic) data is used by most state emission programs.

• Global OBD-II displays often use hexadecimal numbers, which use 16 numbers instead of 10.

• The numbers 0 to 9 (zero counts as a number) make up the first 10 and then capital letters A to F complete the 16 numbers.

• To help identify the number as being in a hexadecimal format, a dollar sign ($) is used in front of the number or letter

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.24

GLOBAL OBD-II

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.25

How Can You Tell Generic from Factory?

• When using a scan tool on an OBD-II-equipped vehicle, if the display asks for make, model, and year, then the factory or enhanced part of the PCM is being accessed. If the generic or global part of the PCM is being scanned, then there is no need to know the vehicle details.

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.26

SUMMARY

1. If the MIL is on, retrieve the DTC and follow the manufacturer’s recommended procedure to find the root cause of the problem.

2. All monitors must have the enable criteria achieved before a test is performed.

3. OBD-II vehicles use common generic DTCs.

4. OBD II includes generic (SAE), as well as vehicle manufacturerspecific DTCs, and data display.

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.27

REVIEW QUESTIONS

1. What does the PCM do during a trip to test emissionrelated components?

2. What is the difference between a type A and type B OBD-II DTC?

3. What is the difference between a trip and a warm-up cycle?

4. What could cause the MIL to flash?

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.28

CHAPTER QUIZ

1. A freeze-frame is generated on an OBD-II vehicle ________.

a. When a type C or D diagnostic trouble code is set

b. When a type A or B diagnostic trouble code is set

c. Every other trip

d. When the PCM detects a problem with the O2S

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.29

CHAPTER QUIZ

2. An ignition misfire or fuel mixture problem is an example of what type of DTC?

a. Type A

b. Type B

c. Type C

d. Type D

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.30

CHAPTER QUIZ

3. The comprehensive component monitor checks computercontrolled devices for_______.

a. Opens

b. rationality

c. shorts-to-ground

d. All of the above

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.31

CHAPTER QUIZ

4. OBD II has been on all passenger vehicles in the United States since ________.

a. 1986

b. 1991

c. 1996

d. 2000

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.32

CHAPTER QUIZ

5. Which is a continuous monitor?a. Fuel system monitor

b. EGR monitor

c. Oxygen sensor monitor

d. Catalyst monitor

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.33

CHAPTER QUIZ

6. DTC P0302 is a ________.a. Generic DTC

b. Vehicle manufacturer-specific DTC

c. Idle speed-related DTC

d. Transmission/transaxle-related DTC

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.34

CHAPTER QUIZ

7. Global (generic) OBD II contains some data in what format?

a. Plain English

b. Hexadecimal

c. Roman numerals

d. All of the above

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.35

CHAPTER QUIZ

8. By looking at the way diagnostic trouble codes are formatted, which DTC could indicate that the gas cap is loose or defective?

a. P0221

b. P1301

c. P0442

d. P1603

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.36

CHAPTER QUIZ

9. The computer will automatically clear a DTC if there are no additional detected faults after ________.

a. Forty consecutive warm-up cycles

b. Eighty warm-up cycles

c. Two consecutive trips

d. Four key-on/key-off cycles

Automotive Engine Performance, 3/eBy James D. Halderman

Copyright © 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 • All rights reserved.37

CHAPTER QUIZ

10.A pending code is set when a fault is detected on ________.

a. A one-trip fault item

b. The first fault of a two-trip failure

c. The catalytic converter efficiency

d. Thermostat problem (too long to closed-loop status)