DIAGNOSIS
- OBD-I[ (On-Board Diagnostic System
)
FO
REFERENC
E
BD-
If
(On-Board Diagnostic system
)
OBD regulations refer to those regulations used in the U
.S
.A
.
In order to detect if the vehicle is emitting harmful exhaust gases into the atmosphere, the OBD system
enables the Engine ECU *' to detect any malfunctions of the engine and exhaust control systems and
warn the driver of such conditions via the "CHECK ENGINE" lamp * z
.
There are two types of OBD regulations, namely OBD- I and OBD-I[
. OBD- I regulations are satisfied
with the diagnostic system that has been conventionally used by Toyota
. OBD-II regulations require the
functions shown in the table below against OBD- I regulations
.
*
i
*z
SAE term
; ECM (
engine control
module)
SAE term
; MIL (malfunction
indicator lamp)
0= Required
.
x =
Not require
d
Required item
OBD- I
OBD-I
I
• Detect malfunctions and turn on "CHECK ENGINE"
lamp
0
(
8 items)
0
(41 items
)
• Standardize malfunction
codes
x
0
• Output Engine ECU data
x
0
(17 items
)
• Freeze-frame data*
x
0
(13 items
)
• Communicate between Engine ECU and
diagnostic tool
x
0
• Standardize diagnostic
tools
x
0
• Standardize diagnostic
connectors
x
0
*An Engine ECU function to store important control data into internal memory during the detection of a
malfunction
.
The main characteristic of OBD-II is the unifica-
tion of diagnostic codes and the use of a
special-purpose tester
. As a result, communica-
tion protocol between the tester and the DLC
(Date Link Connector) and Engine ECU are stan-
dardized
. Furthermore, in the case of OBD-II,
measurement of engine rpm and inspection of
each function of the Engine ECU cannot be per-
formed without using a special-purpose tester
.
Toyota employs a system in which original
functions have been added to those required by
OBD-II regulations
. The following describes
some of the major differences between
Toyota's conventional OBD system and the
new OBD system (OBD-II) provided in vehicles
sold in the U
.S
.A
. and Canada
.
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