DID7X±01
FI0534
D13872
Hand±Held Tester
DLC3
DI±40
± DIAGNOSTICSENGINE
234 Author: Date:
2005 SEQUOIA (RM1146U)
DIAGNOSIS SYSTEM
1. Description
When troubleshooting On±Board Diagnostic (OBD ll) ve-
hicles, the vehicle must be connected to 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 Indicator Light (MIL)
on the instrument panel when the computer detects a
malfunction in: 1) the emission control system/compo-
nents, or 2) the powertrain control components (which af-
fect vehicle emissions), or 3) the computer. In addition,
the applicable Diagnostic Trouble Codes (DTCs) pre-
scribed by SAE J2012 are recorded in the ECM memory
(See page DI±58).
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 hand±held tes-
ter). The DTC includes SAE controlled codes and manufacturer
controlled codes. SAE controlled codes must be set according
to the SAE, while manufacturer controlled codes can be set by
a manufacturer with certain restrictions (See the DTC chart on
page DI±58).
2. NORMAL MODE AND CHECK MODE
The diagnosis system operates in ºnormal modeº during normal
vehicle use. In ºnormal modeº, 2 trip detection logic* is used to
ensure accurate detection of malfunctions. A ºcheck modeº is
also available to technicians as an option. In ºcheck modeº, 1
trip detection logic is used for simulating malfunction symptoms
and increasing the system's ability to detect malfunctions, in-
cluding intermittent malfunctions (See page DI±11).
3. 2±TRIP DETECTION LOGIC
When a malfunction is first detected, the malfunction is tempo-
rarily stored in the ECM memory. This is known as 1st trip detec-
tion. If the ignition switch is turned OFF and then ON again, and
the same malfunction is detected again, the MIL will illuminate.
This is known as 2nd trip detection.
DIDIZ±01
D14150
D13872DLC3
OBD II Scan Tool
(Hand±held Tester)
CAN VIM
D14151
DLC3
1314 1516 12 11 10 9 12345678 DI±562
± DIAGNOSTICSAUTOMATIC TRANSMISSION
756 Author: Date:
2005 SEQUOIA (RM1146U)
DIAGNOSIS SYSTEM
DESCRIPTION
When troubleshooting On±Board Diagnostic (OBD II) vehicles,
the vehicle must be connected to the OBD II scan tool (comply-
ing with SAE J1987). Various data output from the vehicle's
ECM can then be read.
OBD II regulations require that the vehicle's on±board comput-
er illuminates the Malfunction Indicator Lamp (MIL) on the
instrument panel when the computer detects a malfunction in:
1) The emission control system/components
2) The powertrain control components (which affect vehicle
emissions)
3) The computer
In addition, the applicable Diagnostic Trouble Codes (DTCs)
prescribed by SAE J2012 are recorded in the ECM memory.
If the malfunction does not reoccur in 3 consecutive trips, the
MIL turns off automatically but the DTCs remain recorded in the
ECM memory.
To check DTCs, connect the scan tool to the Data Link Connec-
tor 3 (DLC3) of the vehicle. The scan tool displays DTCs, the
freeze frame data and a variety of the engine data.
The DTCs and freeze frame data can be erased with the scan
tool (See page DI±565).
NORMAL MODE AND CHECK MODE
The diagnosis system operates in ºnormal modeº during normal
vehicle use. In normal mode, º2±trip detection logicº is used to
ensure accurate detection of malfunctions. ºCheck modeº is
also available to technicians as an option. In check mode,
º1±trip detection logicº is used for simulating malfunction symp-
toms and increasing the system's ability to detect malfunctions,
including intermittent malfunctions.
2±TRIP DETECTION LOGIC
When a malfunction is first detected, the malfunction is tempo-
rarily stored in the ECM memory (1st trip). If the ignition switch
is turned OFF and then ON again, and the same malfunction is
detected again, the MIL will illuminate.
