Isuzu KB P190. Manual - part 919

Powertrain Interface Module – V6 

Page 6E1–15 

 

4 Diagnostics 

4.1 

Diagnostic General Descriptions 

The powertrain interface module (PIM) diagnostic procedure is organised in a logical structure that begins with the 
Diagnostic System Check. The Diagnostic System Check directs the diagnostic procedure to the logical steps or 
appropriate diagnostic table required to diagnose a PIM fault condition. 

The diagnostic tables locate a faulty circuit or component through a logical based process of elimination. Correct use of 
the diagnostic tables is essential to reduce diagnostic time and to prevent misdiagnosis. 

In addition, the Diagnostic System Check provides the following information: 

• 

identification of the PIM, 

• 

condition of the diagnostic circuit, and 

• 

identification and status of the DTCs if present. 

Diagnostic Trouble Code (DTC) Tables 

The diagnostic procedure is directed to a diagnostic trouble code (DTC) table if there are DTCs currently stored in the 
PIM. 

The diagnostic tables are designed to locate a faulty circuit or component through a logical based process of elimination. 
The diagnostic tables are developed with the following assumptions: 

• 

the vehicle functioned correctly at the time of assembly, 

• 

there are no multiple faults, and 

• 

the problem currently exists. 

Multiple DTCs 

When performing a DTC check and there are multiple DTCs, the diagnostic process must begin with the most likely DTC 
that may trigger other DTCs. 

Knowledge of the PIM and Tech 2 limitations are important to reduce diagnostic time and to prevent misdiagnosis. Refer 
to 7.1 

Diagnostic Requirements, Precautions and Preliminary Checks. 

Diagnostic Trouble Codes (DTCs) 

When the ignition switch is turned on, the PIM performs an internal integrity check that detects and isolates any internal 
faults. The PIM also monitors the direct input switches such as the cruise control and the serial data bus for messages 
from the control modules on the GM LAN bus. If a fault is detected by the PIM, it will log a Diagnostic Trouble Code 
(DTC) that represents the fault detected. The DTCs stored in the PIM may be accessed using Tech 2. 

Status of DTCs 

The PIM designates the DTCs logged into a Current or History DTC. 

Current DTCs 

If the fault condition that triggers the DTC is present during the last PIM self test, that DTC will be designated as a current 
DTC. 

History DTCs 

If the fault condition that triggers the DTC is not present during the last PIM self test, that DTC will be designated as a 
history DTC. 

Conditions for Clearing DTCs 

• 

If there is no DTC logged in the current PIM self test, the current DTC will be cleared. 

• 

If there is no DTC logged after 100 consecutive drive cycles, the history DTC will be cleared. 

Powertrain Interface Module – V6 

Page 6E1–16 

 

Tech 2 PIM Diagnostic Tests 

Tech 2 Limitations 

Some DTCs trigger other DTCs to set, which causes Tech 2 to display multiple DTCs. In those situations, Tech 2 may 
display more DTCs than is needed to rectify a fault. 

When Tech 2 displays an output function, it displays only the command given by the PIM. If a connector is disconnected, 
that fault will not register in the PIM output function. Tech 2 does not verify the command action. 

The service technician must understand the system being diagnosed as well as the correct use and limitations of Tech 2 
to be able to perform diagnostic procedures efficiently and successfully. 

Tech 2 Intermittent Fault Tests 

The following are lists of Tech 2 diagnostic tests that may be used to diagnose intermittent faults: 

• 

Wiggle test the suspected PIM wiring harness and connector while observing Tech 2 operating parameters of the 
circuit being tested. If Tech 2 read-out fluctuates during this procedure, check the wiring harness circuit for loose 
connection. 

• 

Road test the vehicle in conditions that trigger the intermittent fault while an assistant observes the suspected Tech 
2 operating parameter data. 

• 

Capture and store data in the Snapshot mode when the fault occurs. The stored data may be replayed at a slower 
rate to aid in diagnostics. Refer to Tech 2 User Instructions for more information on the Snapshot function. 

• 

Operate suspected components to test their operation using Tech 2 Output Control Data. 

Powertrain Interface Module – V6 

Page 6E1–17 

 

5 

GM LAN Serial Communication 
Circuit 

 

Figure 6E1 – 12 

Powertrain Interface Module – V6 

Page 6E1–18 

 

6 

Wiring Diagram and Connector 
Chart 

6.1 Wiring 

Diagrams 

 

Figure 6E1 – 13