3176B INDUSTRIAL ENGINE Caterpillar

Section 4: Troubleshooting With A Diagnostic Code

Usage:

Diagnostic Codes

Diagnostic codes are used by the electronic system to alert the operator that a problem exists and indicates to the service technician the nature of the problem.

Diagnostic Codes may be viewed using Electronic Service Tools (ET or ECAP) or the various electronic display modules. The CID, or Component IDentifier, tells which component in the system the diagnostic code is for. The FMI, or Failure Mode Identifier indicates what the failure mode is.

The code number will direct you to a procedure in Functional Test Procedures. Do not confuse diagnostic codes with diagnostic events. Events can be logged in the ECM to track information about the engine. An example would be a low oil pressure event. An event is generated when the engine oil pressure is low but not out of range for the sensor. This does not indicate a problem with the sensor, rather it indicates a problem with the engine oil pressure.

Active Diagnostic Codes

An ACTIVE diagnostic code represents a problem with the electronic control system that should be investigated and corrected as soon as is practical. When an ACTIVE diagnostic code is generated, a display module such as Electronic Monitoring may indicate the diagnostic code. If the condition generating the diagnostic occurs only for a brief moment, the message will disappear and the diagnostic code will be LOGGED in the ECM memory.

To troubleshoot an active diagnostic code, refer to the Diagnostic Code Cross Reference to Functional Test Procedures in the beginning of this manual under the specific code number.

Logged Diagnostic Codes

When the ECM generates a diagnostic code, it usually logs the code in permanent memory within the ECM. The ECM has an internal diagnostic clock and will record the hour of the first occurrence, the hour of the last occurrence and the number of occurrences of the code. Knowing when and how often the code was generated can be a valuable indicator when troubleshooting intermittent problems.

NOTE: The ECAP Electronic Service Tool can be used but does not support all logged codes. Logged codes can be retrieved or erased using an Electronic Service Tool. Logged diagnostic codes will automatically be deleted if no additional occurrences are recorded in 100 hours. When investigating logged diagnostic codes, keep in mind the following information.

Some diagnostic codes may be sensitive, and may log occurrences that did not result in operator or pilot complaints. If the time the code was logged does not correlate to a complaint, there may be nothing to fix.

The most likely cause of an intermittent problem is a faulty connection or damaged wiring. Next likely is a component failure (sensor or switch). Least likely is failure of the ECM itself.

Diagnostic codes that are logged repeatedly may indicate a problem that needs special investigation.

To troubleshoot a logged diagnostic code, refer to the Diagnostic Code Cross Reference to Functional Test Procedures in the beginning of this manual under the specific code number.

The code number will direct you to a procedure in Functional Test Procedures. If the symptoms continue, use the proper procedure for troubleshooting the symptoms that have been experienced by the operator. Refer to Troubleshooting Without A Diagnostic Code.

NOTE: Always clear logged diagnostic codes after investigating and correcting the problem which generated the code.

Using ET to Display Active Diagnostic Codes

1. Connect ET and the Communication Adapter Tool to the Service Tool Connector and run the ET Program.

2. Turn the keyswitch to the ON position, engine OFF.

3. Select the Display Active Diagnostics option from the Tools Menu.

4. Each Diagnostic Code CID and FMI are listed and followed by a text description.

ET Active Diagnostic Code Screen

Using ET to Display Logged Diagnostic Codes

1. Connect ET and the Communication Adapter Tool to the Service Tool Connector and run the ET Program.

2. Turn the keyswitch to the ON position, engine OFF.

3. Select the Display Logged Diagnostics option from the Tools Menu.

4. Each Diagnostic Code CID and FMI are listed and followed by a text description.

Using ET to Display Status

1. Connect ET and the Communication Adapter Tool to the Service Tool Connector and run the ET Program.

2. Turn the keyswitch to the ON position, engine OFF.

3. Select the Display Status option from the Tools Menu.

ET Status Screen

Engine Monitoring Programmed to WARNING

Engine Monitoring Programmed to DERATE

ECM Snapshot

The ECM can record a "snapshot" of engine/unit parameters for a period of 13 seconds surrounding an event. The event is either a diagnostic code or an external trigger.

DO NOT replace electronic components based on snapshot data alone. The snapshot information is stored in frames every 0.24 seconds (if externally triggered) or every 0.48 seconds (if diagnostic code triggered). Frequently, the parameters are changing faster or slower than 0.24 seconds, the result will be a misdiagnosed problem if too much is interpreted from this information.

DO NOT attempt to interpret the information and analyze how the engine is operating from this historical information. Looking at this information under a "microscope" will lead to misdiagnoses because some parameters are not what are expected, even though they are completely unrelated to the problem under investigation.

When to Use a Snapshot

Use the snapshot data feature ONLY to help determine engine/unit operating conditions when an intermittent problem occurs. If an intermittent diagnostic code is causing problems, use the snapshot data to determine if the problem occurs (or appears to occur) at specific engine rpm or unit speed ranges, coolant temperature ranges, etc. Use this data to attempt to duplicate these conditions and allow the code to reoccur.

Engine Snapshot Data

Whenever most diagnostic codes occur, the ECM records the time (in engine hours), as well as engine operating parameters for 9.6 seconds before and 3.4 seconds after the diagnostic code. The engine operating parameters recorded are similar to those in the ECAP or ET status screens. Not all ECAP or ET status screens or parameters are recorded.

The Engine Snapshot is triggered from the ECAP or Electronic Technician Electronic Service Tools.

Diagnostic Code Triggered Snapshot

When viewing diagnostic triggered snapshots, the ECM sets a sensor value with an ACTIVE diagnostic code to a default value when the code is Active. The sensor value will suddenly jump to a specific value at the trigger point and remain there for the rest of the snapshot frames.

After the diagnostic code occurs, the ECM records many of the status parameters available on the Electronic Service Tool. The ECM records this information for 9.6 seconds before the code occurs, and 3.4 seconds after the code.

External Triggered Snapshot

If desired, a snapshot can be externally triggered using an Electronic Service Tool. The snapshot can be triggered from the Display/Trigger Snapshot screen, located under the Display Diagnostic Messages screen (follow the on-screen instructions).

ECM Storage of Snapshots

The ECM can store up to six diagnostic code triggered snapshots, and four externally triggered snapshots. They are stored in a "circular buffer". The newest snapshot will replace the oldest if a seventh diagnostic code triggered snapshot or fifth externally triggered snapshot is taken.

The ECM stores the snapshots in memory that is maintained through the Unswitched +Battery connection. If the Unswitched +Battery connection is disconnected, or if the unit batteries are disconnected, the snapshot information is cleared.

The snapshots can also be manually cleared using an Electronic Service Tool. Snapshots, like most diagnostic codes are automatically cleared by the ECM after 100 hours of operation.

Reference Sheet For Diagnostic Codes.

Diagnostic Terminology

Component Identifier (CID): Two or three digit code which is assigned to each component or system.
Event Identifier (EID): Two or three digit code which is assigned to each component or system.
Failure Mode Identifier (FMI): Type of failure the component experienced (adopted from SAE standard practice J1587 diagnostics).

Active Code: The CID and FMI can be sent through the data link through the display module or through the Communication Adapter Tool, then to the Electronic Service Tool or various electronic display modules.
Logged Code: The diagnostic will be entered into the permanent memory (Diagnostic Log) when it becomes active. The number of occurrences will be saved in the "good to faulty counter" in the permanent memory (Diagnostic Log). First and last occurrence time (engine hours) will also be saved in the permanent memory (Diagnostic Log). This information is then available for display on the Electronic Service Tool.