Isuzu 2008MY N Series Workshop Manual page 58

Scan Tool Does Not Communicate with
Keyword Device
Specification)
Circuit Description
The ECM, transmission control module (TCM) and
supplemental restraint system (SRS) control unit
communicates with the scan tool over the Keyword
2000 serial data link. The hill start aid (HSA) control unit
communicates with the Keyword 82 serial data link.
However, the ECM, TCM, electric hydraulic control unit
(EHCU) and the data recording module (DRM)
communicate with each other over the controller area
network (CAN) link. The CAN link is not used for
communication with the scan tool and is shared only
among each module.
Circuit/ System Testing Scan Tool Does Not Communicate with Keyword Device (Except Euro 4
Specification)
Step
Did you perform the Diagnostic System Check
1
- Engine Controls?
1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. Attempt to communicate with the listed control
modules.
• ECM
• Transmission
(Smoother only)
• Hill start aid (HSA) control unit
2
(If so equipped)
• Supplemental restraint system (SRS)
control unit (If so equipped)
• Immobilizer Control Unit (ICU)
(If so equipped)
Does the scan tool communicate with any of
the listed control modules?
Does the scan tool communicate with the
ECM?
3
Notice: If no Smoother transmission is installed,
skip to Step 5.
4
Does the scan tool communicate with the
TCM?
Notice: If no HSA system is installed, skip to Step
6.
5
Does the scan tool communicate with the
HSA control unit?
(Except Euro
Action
control module (TCM)
Engine Control System (4HK1)
Diagnostic Aids
4
The following conditions will cause a loss of Keyword
serial data communication between the TCM, SRS
control unit and HSA control unit or between the scan
tool any control module:
• A Keyword serial data circuit open
• A Keyword serial data circuit shorted to ground
• A Keyword serial data circuit shorted to voltage
• An internal condition within a module or connector
on the Keyword serial data circuit, that causes a
short to voltage or ground to the Keyword serial
data circuit.
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls
Connector End Views or ECM Connector End Views
Value(s)
—
—
—
—
—
Yes
Go to Diagnostic
System Check -
Go to Step 2 Engine Controls
Go to Step 3 Go to Step 9
Go to Lost
Communication with
The Engine Control
Go to Step 4 Module (ECM)
Go to Diagnostic
System Check -
Transmission
Controls in Section
5A Transmission
Go to Step 5 Control System
Go to Diagnostic
System Check -
HSA Controls in
Go to Step 6 Section 4E HSA
1A-55
No