All about Caterpillar's SPN, FMI, CID, and MID codes and how to decipher them

February 07, 2021

Key advantage of using telematics like VisionLink or is having immediate access to fault codes. Some fault codes don't require immediate action, but others may signal a critical safety or breakdown concern. As a fleet owner or equipment manager, you want to know about this fault code as it happens.

If you use VisionLink's website, these error codes will appear with usually clear description, like "Right Joystick Thumbwheel Position Sensor-Voltage Above Normal" or "Brake Oil Temperature Sensor (Right Rear)-Voltage Below Normal". But sometimes all you'll find is codes, like "MID 82, CID 168, FMI 4" which isn't very helpful. If you're importing VisionLink data via their API, then the AEMP 2.0 standard will contain only coded information, leaving with you with the complex task of interpreting these codes.  Here's a quick summary of how to do so.

SPN Suspect Parameter Numbers.
These are diagnostic fault code referring to specific components or system circuits. You can find a fairly complete list of SPNs for Caterpillar equipment here.

MID Module Identifier.
Newer Caterpillar machines use Caterpillar Electronic Controls, which can help pinpoint specific modules, components and failure modes. MID identifies the specific electronic control module that diagnosed the fault, like MID 116- Integrated Brake Control. Here's a list of Caterpillar MIDs.

CID Component Identifier
The CID helps pinpoint a specific circuit or system, usually within the MID. E.g. CID 854 - Brake Oil Temperature Sensor (Right Rear), is related to MID 116. Our top 3 CID fault codes at Clue are 3565 (Air Conditioner Suction Pressure Sensor), 1961 (Hydraulic Oil Temperature Sensor) and 1469 (SAE J1939 Data Link). There are hundreds of CIDs, and here's a useful list.

FMI Failure Mode Identifier
These are essentially the "message" from the circuit affected. For example, MID 116-CID 854 may report FMI 4, “Voltage below normal”. From what we can see amongst hundreds of thousands of fault code at Clue, he most common FMI codes are 3 (“Voltage above normal”) and 9 (“Abnormal update rate”). A fairly complete list of FMI codes is here.

The advantage of using a platform like Clue, is that you won't have to worry about interpreting any of these codes. Your operators, mechanics and equipment managers will get all fault codes in plain english (or Spanish - we're bilingual). Clue does all the hard work of interpreting SPN, MID, CID, and FMI codes for you. Best of all, we do that for all OEMs, not just Caterpillar. To learn more, contact us today via [email protected].

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