GENERAL INFORMATION
- A large number of ECU controlled systems are used in the TOYOTA TUNDRA.
In general, ECU controlled systems are considered to be very intricate,
requiring a high level of technical knowledge to troubleshoot. However,
most problem checking procedures only involve inspecting the ECU
controlled system's circuits one by one. An adequate understanding of
the system and a basic knowledge of electricity is enough to perform
effective troubleshooting, accurate diagnoses and necessary repairs.
1. TROUBLESHOOTING PROCEDURES
- The troubleshooting procedures consist of diagnosis procedures for when a
DTC is stored and diagnosis procedures for when no DTC is stored. The
basic idea is explained in the following table.
|
Procedure Type |
Details |
Troubleshooting Method |
|
DTC Based Diagnosis |
The diagnosis procedure is based on the DTC that is stored.
|
The malfunctioning part is identified based on the DTC detection conditions using a process of elimination.
The possible trouble areas are eliminated one-by-one by use of the Techstream and inspection of related parts.
|
|
Symptom Based Diagnosis
(No DTCs stored) |
The diagnosis procedure is based on problem symptoms.
|
The malfunctioning part is identified based on the problem symptoms using a process of elimination.
The possible trouble areas are eliminated one-by-one by use of the Techstream and inspection of related parts.
|
- Vehicle systems are complex and use many ECUs that are difficult to
inspect independently. Therefore, a process of elimination is used,
where components that can be inspected individually are inspected, and
if no problems are found in these components, the related ECU is
identified as the problem and replaced.
- It is extremely important to ask the customer about the environment and
the conditions present when the problem occurred (Customer Problem
Analysis). This makes it possible to simulate the conditions and confirm
the symptom. If the symptom cannot be confirmed or the DTC does not
recur, the malfunctioning part may not be identified using the
troubleshooting procedure, and the ECU for the related system may be
replaced even though it is not defective. If this happens, the original
problem will not be solved.
- In order to prevent endless expansion of troubleshooting procedures, the
troubleshooting procedures are written with the assumption that
multiple malfunctions do not occur simultaneously for a single problem
symptom.
- To identify the malfunctioning part, troubleshooting procedures narrow
down the target by separating components, ECUs and wire harnesses during
the inspection. If the wire harness is identified as the cause of the
problem, it is necessary to inspect not only the connections to
components and ECUs but also all of the wire harness connectors between
the component and the ECU.
DIAGNOSTIC TESTER 2. DESCRIPTION System
data and the Diagnostic Trouble Codes (DTCs) can be read from the Data
Link Connector 3 (DLC3) of the vehicle. When the system seems to be
malfunctioning, use the Techstream* to check for a malfunction and
perform repairs. HINT: *: Techstream is the name for the diagnostic tester in North America.
3. DATA LINK CONNECTOR 3 (DLC3) (a)
The vehicle's ECU uses the ISO 15765-4 communication protocol. The
terminal arrangement of the DLC3 complies with SAE J1962 and matches the
ISO 15765-4 format.  |
Terminal No. (Symbols) | Terminal Description |
Condition | Specified Condition | |
7 (SIL) - 5 (SG) | Bus "+" line |
During transmission | Pulse generation | |
4 (CG) - Body ground |
Chassis ground | Always |
Below 1 Ω | |
5 (SG) - Body ground |
Signal ground | Always |
Below 1 Ω | |
16 (BAT) - Body ground |
Battery positive | Always |
11 to 14 V | |
6 (CANH) - 14 (CANL) |
CAN bus line | Ignition switch OFF* |
54 to 69 Ω | |
6 (CANH) - 4 (CG) | HIGH-level CAN bus line |
Ignition switch OFF* |
200 Ω or higher | |
14 (CANL) - 4 (CG) | LOW-level CAN bus line |
Ignition switch OFF* |
200 Ω or higher | |
6 (CANH) - 16 (BAT) | HIGH-level CAN bus line |
Ignition switch OFF* |
6 kΩ or higher | |
14 (CANL) - 16 (BAT) |
LOW-level CAN bus line |
Ignition switch OFF* |
6 kΩ or higher | NOTICE: *:
Before measuring the resistance, leave the vehicle as is for at least 1
minute and do not operate the ignition switch, any other switches, or
the doors. If the result is not as specified, the DLC3 may have a malfunction. Repair or replace the harness and connector.
(b)
Connect the cable of the Techstream to the DLC3, turn the ignition
switch ON and attempt to use the tester. If the display indicates that a
communication error has occurred, there is a problem either with the
vehicle or with the tester.
HINT:
- If communication is normal when the tester is connected to another vehicle, inspect the DLC3 of the original vehicle.
- If communication is still not possible when the tester is connected to
another vehicle, the problem may be in the tester itself. Consult the
Service Department listed in the tester's instruction manual.
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