DIDYQ-01
FI0534
- DIAGNOSTICSAUTOMATIC TRANSMISSION
DI-361
554 Author: Date:
PRE-CHECK
1. DIAGNOSIS SYSTEM
(a) Description
(1) When troubleshooting OBD II vehicles, the only dif-
ference from the usual troubleshooting procedure
is that you need to connect an OBD II scan tool com-
plying with SAE J1987 or a hand-held tester to the
vehicle, and read off various data output from the
vehicle's ECM.
(2) OBD II regulations require that the vehicle's on-
board computer illuminate the Malfunction Indicator
Lamp (MIL) on the instrument panel when the com-
puter detects a malfunction in the computer itself or
in the drive system components which affect the ve-
hicle emissions. In addition to the MIL illuminating
when a malfunction is detected, the applicable
DTCs prescribed by SAE J2012 are recorded in the
ECM memory (See page DI-381).
If the malfunction does not occur in 3 consecutive trips, the MIL
goes off but the DTCs remain in the ECM memory.
(3) To check the DTCs, connect the OBD II scan tool or
hand-held tester to the DLC3 of the vehicle. The
OBD II scan tool or hand-held tester also enables
you to erase the DTCs and check freeze frame data
and various forms of engine data (For instruction
book).
(4) The DTCs include SAE controlled codes and
Manufacturer controlled codes. SAE controlled
codes must be set as prescribed by the SAE, while
Manufacturer controlled codes can be set freely by
a manufacturer within the prescribed limits (See the
DTC chart on page DI-381).
(5) The diagnosis system operates in the normal mode
during the normal vehicle use, and also has a check
mode for technicians to simulate malfunction symp-
toms and perform troubleshooting. Most DTCs use
2 trip detection logic(*) to prevent erroneous detec-
tion. By switching the ECM to the check mode when
troubleshooting, the technician can cause the MIL
to light up for a malfunction that is only detected
once or momentarily. (hand-held tester).
(6) *2 trip detection logic:
When a malfunction is first detected, the malfunc-
tion is temporarily stored in the ECM memory. If the
same malfunction is detected again during the se-
cond test drive, this second detection causes the
MIL to illuminate.
DIC20-01
A05658
A07061DLC3
Hand-Held Tester
- DIAGNOSTICSENGINE
DI-3
196 Author: Date:
PRE-CHECK
1. DIAGNOSIS SYSTEM
(a) Description
When troubleshooting On-Board Diagnostic (OBD
ll) vehicles, the vehicle must be connected to the
OBD ll scan tool (in compliance with SAE J1978) or
the hand-held tester. Various data output from the
vehicle's ECM can then be read.
OBD ll regulations require that the vehicle's on-
board computer illuminates the Malfunction Indica-
tor Light (MIL) on the instrument panel when the
computer detects a malfunction in: 1) the emission
control system/components, or 2) the powertrain
control components (which affect vehicle emis-
sions), or 3) the computer. In addition, the applica-
ble Diagnostic Trouble Codes (DTCs) prescribed by
SAE J2012 are recorded in the ECM memory
(See page DI-36).
If the malfunction does not reoccur in 3 consecutive trips, the
MIL goes off automatically but the DTCs remain recorded in the
ECM memory.
To check the DTC, connect the hand-held tester or
OBD II scan tool to the Data Link Connector 3
(DLC3) of the vehicle. The hand-held tester or OBD
II scan tool also enables you to erase the DTC and
check the freeze frame data and various forms of
engine data (See the instruction manual for the
OBD ll scan tool or the hand-held tester). The DTC
includes SAE controlled codes and manufacturer
controlled codes. SAE controlled codes must be set
according to the SAE, while manufacturer con-
trolled codes can be set by a manufacturer with cer-
tain restrictions (See the DTC chart on page
DI-36).
