toyota training course t874 engine control systems II ch02

Section 2

On-Board Diagnostics (OBD II)

Slide 10

OBD Generations 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.
OBD

OBD II

CAN OBD II

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
phased in by 2008.

Toyota Engine Control Systems I

Course 852

9


Diagnostic Toolset

On-Board Diagnostics (OBD II)

Slide 11

Diagnostic Toolset 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
General OBD II Scan Tool
or Techstream Procedure

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.

10

TOYOTA Technical Training


Diagnostic Trouble Codes (DTC)

On-Board Diagnostics (OBD II)

Slide 12

TIS Techstream Diagnostic
Trouble Codes Screen

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
(DTCs)

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

Toyota Engine Control Systems I

Course 852

11


Drive Patterns

On-Board Diagnostics (OBD II)

Slide 1

T874f509, T874f310,Slide
T874f508
13

Confirmation Driving
Pattern

Universal Trip Driving
Pattern

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.

NOTE: 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.

12

TOYOTA Technical Training


Freeze Frame Data

On-Board Diagnostics (OBD II)

Slide 1

T874f509, T874f310,Slide
T874f508
14

Freeze Frame Data

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.

Toyota Engine Control Systems I

Course 852

13


Data List

On-Board Diagnostics (OBD II)

Slide 1

T874f509, T874f310,Slide
T874f508
15

Data List

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.

14

TOYOTA Technical Training

Active Test

On-Board Diagnostics (OBD II)

Slide 1

T874f509, T874f310,Slide
T874f508
16

Active Test

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.

Toyota Engine Control Systems I

Course 852

15


Monitors and Malfunction Indicator Lamp (MIL)

On-Board Diagnostics (OBD II)

Slide 1

T874f509, T874f310,Slide
T874f508
17

Monitors

Malfunction Indicator Lamp
(MIL)

16

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.

TOYOTA Technical Training