toyota training course t874 engine control systems II ch02

On-Board Diagnostics OBD IISection 2 Slide 10 The primary objective of on-board diagnostic OBD systems is to detect and report any engine control system malfunctions.. OBD II standards g

On-Board Diagnostics (OBD II)

Section 2

Slide 10

The primary objective of on-board diagnostic (OBD) systems is to detect and report any engine control system malfunctions This helps prevent excessive vehicle emissions (from damaged or malfunctioning circuits and/or components) and to lessen the possibility of further damage OBD

is capable of detecting shorts and opens in most sensor electrical circuits and in some actuator circuits Later models equipped with the OBD II system can also detect component and system performance

In 1988, the California Air Resources Board (CARB) set the requirement that all vehicles have a system that could identify faults in the emission and powertrain system This is recognized as OBD I

At the same time OBD requirements were set, CARB also set the requirements for OBD II OBD II was required by the federal government

on all vehicles beginning in 1996 OBD II standards greatly enhanced the on-board diagnostic system’s capabilities and changed the way technicians troubleshoot engine and emission control systems

CAN, which stands for Controller Area Network, is a standard (or

“protocol”) for high-speed electronic communication CAN OBD II requirements do not significantly change the way technicians troubleshoot engine and emission control systems Instead, CAN improves the speed and accuracy of information exchange among the vehicle’s ECM/ECUs, and between the vehicle and the diagnostic tester CAN OBD II must be

OBD Generations

OBD

OBD II

CAN OBD II

The diagnostic toolset consists of the TIS techstream, also known as the Techstream or the “scan tool.” Depending on the vehicle you are working

on and the nature of the customer concern, this tool is extremely valuable for gathering large quantities of diagnostic data in a relatively short period of time For troubleshooting engine control system concerns, the Techstream allows you to quickly perform the following functions:

• Read and define Diagnostic Trouble Codes (DTCs)

• Display serial data stream containing sensor, actuator, and diagnostic information

• Store and playback snapshot data

• Display OBD II monitor status and results

• Test sensors and actuators dynamically using active tests

If the Techstream cannot communicate with ECU controlled systems when connected to DLC3, the ignition switch is ON, and the Techstream

is on, then there is a problem on the vehicle side or tool side

1) If communication is normal when the Techstream is connected to

another vehicle, inspect the diagnosis data link line (Bus-line) or ECM (ECU) power circuit of the vehicle

2) If communication is still not possible when the Techstream is

connected to another vehicle, the problem is probably in the Techstream itself Check the Techstream Operator’s Manual or call Techstream support for help

Diagnostic Toolset On-Board Diagnostics (OBD II)

Slide 11

Diagnostic Toolset

General OBD II Scan Tool

or Techstream Procedure

The TIS Techstream displays all ECU specific DTC information on one screen, including Code name and Description, and specifies it as a Current, Pending, History and/or Permanent DTC

The numbers below correspond to the number callouts in the illustration

1) These columns display the DTC as Current, Pending, History and/

or Permanent DTC

2) Use the eraser button to clear DTC(s), monitor information, etc 3) To access Freeze Frame data, click on the snowflake icon next to

the DTC, or highlight the DTC and click the snowflake button at the bottom of the screen

4) Use the disc button to store DTC(s), Freeze Frame, and Monitor

information to the Stored Data tab If DTCs are not stored from the DTC or Monitor screens, the current DTC and Monitor Status/ Results will not be stored to the Stored Data tab and cannot be accessed later

5) The current user is displayed here Double-click the current user to

access the Change/Create User pop-up window

Diagnostic Trouble Codes are set when the ECM detects a malfunction in

a monitored component or system There are two types of DTCs:

• One Trip DTCs

• Two Trip DTCs

TIS Techstream Diagnostic

Trouble Codes Screen

Diagnostic Trouble Codes

(DTCs)

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Drive Patterns On-Board Diagnostics (OBD II)

NOTE:

The Confirmation Driving Pattern is used to provide DTC specific vehicle operation to confirm normal judgment This driving pattern is specific for each DTC and system monitoring strategy After normal judgment is obtained the Universal Trip Driving Pattern will need to be completed to fully clear the permanent DTC column (or three consecutive drive cycles with normal judgment)

The Universal Trip Driving Pattern (UTDP) can be performed consecutively with the Confirmation Drive Pattern Be sure to let the engine idle for 30 or more seconds before proceeding and drive the vehicle at 25 mph or more for at least 5 minutes

It is possible to complete the drive pattern even if the vehicle decelerates below 25 mph during drive cycle provided that the vehicle is driven at

or above 25 mph for a total of 5 minutes Allow 10 minutes or more

to elapse from the time the engine is started and cycle the ignition to confirm the permanent DTCs have been cleared

Confirmation Driving

Pattern

Universal Trip Driving

Pattern

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The ECM records vehicle and driving condition information the moment a DTC is stored This “Freeze Frame data” can be helpful when troubleshooting, especially if the problem is intermittent or cannot be duplicated during a test drive

Earlier model vehicles record one (1) Freeze Frame per applicable DTC

at the time the DTC set

Later model vehicles (CAN OBD II) store five sets of data:

• Three sets of data before the DTC was set

• One set of data when the DTC was set

• One set of data after the DTC was set Freeze Frame data shows the input value of all system sensors and the output conditions commanded by the ECM at that precise moment in time

Freeze Frame Data

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Data List On-Board Diagnostics (OBD II)

The Data List provides important current parameter values.

The numbers below correspond to the number callouts in the illustration

1) To create a custom data list, select all desired parameters, and then

click the New List button.

2) To remove parameters from a data list, select the parameters, and

then click the Remove button.

3) The Data List Manager can also be used to create a custom data

list

4) Use the data list pull-down menu to access optional data lists Note: If a custom list has been created, it can be accessed from the

pull-down menu at any time during the session

5) Use the Graph button to graph parameters.

6) Anytime the Record button is enabled (red), a snapshot can be

recorded

7) The ms reading displays the current refresh interval A smaller

number indicates a faster refresh rate (more real-time data) Most CAN OBD II vehicles will display a reading around 200 ms OBD

II vehicles (non-CAN) will display a much larger (slower) refresh interval To reduce the refresh interval, reduce the number of parameters of the data list by making a custom data list

Data List

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Active tests allow the Techstream user to control specific components

in order to test them for proper operation and electrical control Active test control windows can be dragged to different parts of the screen by clicking on the top of the control window

Active Test

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Monitors and Malfunction Indicator Lamp (MIL) On-Board Diagnostics (OBD II)

To meet OBD II regulations, the ECM monitors various engine systems and components and tests their performance In addition to monitoring and testing systems and components that are obviously emissions-related, such as engine misfire and EVAP systems, the ECM may also monitor general engine components such as the cooling system thermostat

When the ECM detects a malfunction that will cause emission levels to exceed a certain level, it turns on the Malfunction Indicator Lamp (MIL) The ECM may also store a Diagnostic Trouble Code (DTC) in memory Depending on the fault, the MIL may be turned OFF if the malfunction does not return during subsequent key cycles

Monitors

Malfunction Indicator Lamp

(MIL)

Slide 17