Circuit Description
A Class 2 serial data communications system is used on this vehicle to allow vehicle modules to communicate and share information with each other. Each bit of information has one of two lengths: long or short. This allows vehicle wiring to be reduced and the transmission and reception of multiple signals over a single wire. The messages carried on Class 2 serial data streams are also prioritized. If two messages attempt to establish communications on the data line at the same time, the message with the higher priority will continue. the message with the lower priority message will wait. If a module cannot respond to the PCM, a DTC is stored.
Conditions for setting the DTC
The PCM cannot communicate with the Integrated Control Module (ICC) also called the Electronic Brake Control Module (EBCM).
Action Taken when the DTC sets
| • | The PCM will record operations at the time the diagnostic sets. This information will be stored in the Freeze Frame and Failure Records buffers. |
| • | A history DTC is stored. |
Conditions for Clearing the DTC
| • | A history DTC will clear after 40 consecutive warm up cycles without a malfunction. |
| • | DTC(s) can be cleared by using a scan tool. |
Diagnostic Aids
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.
Any circuitry, that is suspected as causing an intermittent complaint, should be thoroughly checked for the following:
| • | Backed out terminals or improper mating. |
| • | Broken locks. |
| • | Improperly formed or damaged terminals. |
| • | Poor terminal to wiring connections. |
| • | Physical damage to the wiring harness. |
| • | Corrosion. |
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and store the Freeze Frame Data and the Failure records on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. This information on the scan tool can be referred to later.
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If the scan tool cannot read serial data from the EBCM, be sure that the scan is working properly on another vehicle.
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The open in the circuit can be narrowed down by determining which modules can communicate with the scan tool.
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If the scan tool can communicate normally with the EBCM once the connectors are disconnected, the PCM is causing the short on the Class 2 serial data circuit.
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Replacement PCMs must be reprogrammed and the crankshaft position system variation procedure must be performed. Refer to the latest Isuzu Technical Communication System (ITCS) information for programming procedures and also refer to the Powertrain Control Module (PCM) .
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If no malfunctions have been found at this point and no additional DTC's were set, refer to Diagnostic Aids for additional checks and information.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | |||
Can the scan tool communicate with the EBCM? | -- | |||
Check the Class 2 serial data circuit for an open and repair an necessary. Was a repair necessary? | -- | |||
4 | Check the Class 2 serial data circuit for a short to ground or to voltage and repair as necessary. Was a repair necessary? | -- | ||
5 | Check the PCM electrical connector for a poor connection and repair as necessary. Was a repair necessary? | -- | ||
Can the scan tool communicate with the EBCM? | -- | Go to Engine Electrical | ||
Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||
8 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | ||
Check if any additional DTCs are set. Are any DTCs displayed that have not been diagnosed? | -- | Go to applicable DTC table | System OK Refer to Diagnostic Aids |
