Caterpillar Fault Codes List – Complete Guide to CAT MID, CID & FMI Diagnostic Codes
Caterpillar machines use an advanced electronic monitoring system to detect faults and record diagnostic trouble codes (DTCs). These codes help technicians quickly identify engine, hydraulic, transmission, electrical, and sensor-related problems.
Whether you operate a CAT excavator, wheel loader, motor grader, dozer, articulated truck, or industrial engine, understanding Caterpillar fault codes can significantly reduce troubleshooting time.
What Are Caterpillar Diagnostic Codes?
Caterpillar Electronic Control Modules (ECM) generate fault codes whenever abnormal operating conditions are detected. These diagnostic codes are typically displayed as:
- MID – Module Identifier
- CID – Component Identifier
- FMI – Failure Mode Identifier
By combining these values, technicians can identify both the affected component and the type of failure.
Understanding MID Codes
MID stands for Module Identifier. It identifies which electronic control module detected the fault.
| MID | Description |
|---|---|
| 27 | Transmission / Chassis Control |
| 30 | Caterpillar Monitoring System |
| 36 | Engine Control Module |
| 39 | Machine Control Module |
| 49 | VIMS Main Module |
| 81 | Transmission Control |
| 82 | Electronic Implement Control |
| 122 | Product Link Module |
Common Caterpillar CID Codes
CID stands for Component Identifier and identifies the specific sensor, switch, actuator, or circuit involved.
| CID | Component |
|---|---|
| 91 | Throttle Position Sensor |
| 100 | Engine Oil Pressure Sensor |
| 105 | Inlet Manifold Temperature Sensor |
| 110 | Engine Coolant Temperature Sensor |
| 168 | Electrical System Voltage |
| 190 | Engine Speed Sensor |
| 247 | SAE J1939 Data Link |
| 254 | Electronic Control Module |
What Is FMI?
FMI stands for Failure Mode Identifier. FMI codes describe the type of failure detected by the ECM.
| FMI | Description |
|---|---|
| 00 | Data Valid But Above Normal Range |
| 01 | Data Valid But Below Normal Range |
| 03 | Voltage Above Normal |
| 04 | Voltage Below Normal |
| 05 | Current Below Normal |
| 06 | Current Above Normal |
| 08 | Abnormal Frequency or Pulse Width |
| 09 | Abnormal Update Rate |
| 12 | Bad Device or Component |
Machines Covered
- Caterpillar Excavators
- Caterpillar Wheel Loaders
- Caterpillar Track Type Tractors
- Caterpillar Motor Graders
- Caterpillar Off Highway Trucks
- Caterpillar Articulated Trucks
- Caterpillar Pipelayers
- Caterpillar Telehandlers
- Caterpillar Engines
- Caterpillar Compact Equipment
Frequently Asked Questions
How do I read a Caterpillar fault code?
Identify the MID, CID, and FMI values. The MID identifies the control module, CID identifies the component, and FMI explains the failure type.
What is CID 168?
CID 168 refers to Electrical System Voltage.
What is CID 190?
CID 190 refers to the Engine Speed Sensor.
What is FMI 04?
FMI 04 means voltage below normal or shorted to ground.
Can CAT ET diagnose these codes?
Yes. Caterpillar Electronic Technician (CAT ET) is the primary diagnostic software used to read and troubleshoot Caterpillar fault codes.
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| CID | Description |
|---|---|
| 91 | Throttle Position Sensor |
| 100 | Engine Oil Pressure Sensor |
| 110 | Engine Coolant Temperature Sensor |
| 168 | Electrical System Voltage |
| 190 | Engine Speed Sensor |
📘 Free Caterpillar Fault Codes PDF
Download the complete Caterpillar MID, CID and FMI fault code reference guide. Perfect for CAT technicians, workshop owners and diagnostic specialists.
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