J1939 Data Link - Abnormal Update Rate (Data Link)
What does CAT-CID247-FMI9 mean?
The CAT-CID247-FMI9 (Caterpillar) diesel fault code means: J1939 Data Link - Abnormal Update Rate (Data Link). This is a serious severity code.
Common Symptoms
- Scan tool communication dropouts
- Dash cluster freezes or flickers
- Lost communication with other modules
Probable Causes (Ranked by Likelihood)
- Broken J1939 twisted pair or terminating resistor missing Very Likely
- Shorted bus wire on CAN_H or CAN_L Likely
- Failed module pulling the bus down Possible
Step-by-Step Diagnostic Procedure
Measure J1939 bus resistance at the diagnostic connector with key off; expect about 60 ohms.
If resistance is wrong, locate both terminators and verify integrity.
Disconnect modules one at a time while monitoring CAT ET to find a module pulling the bus down.
Inspect the twisted pair for chafing, pinches, and moisture at splice packs.
Frequently Asked Questions
What does CAT code CID247-FMI9 mean?
CAT code CID247-FMI9 (J1939 Data Link - Abnormal Update Rate (Data Link)) is a serious-severity fault on Caterpillar on-highway diesel engines. CID 247 is the J1939 Data Link, measuring vehicle J1939 bus communications. FMI 9 (Abnormal Update Rate (Data Link)) indicates the specific fault mode. Use CAT ET to confirm before replacing parts. Diagnose with CAT ET (Electronic Technician) software.
Can I drive my truck with CAT code CID247-FMI9?
Short distances may be acceptable, but running long with this fault risks progressive damage or forced derate. Address promptly.
How much does it cost to fix CAT CID247-FMI9?
Typical repair is $300-$1500. Sensor / wiring fixes fall at the low end; injector, HEUI pump, turbo, or aftertreatment work falls at the high end. CAT dealer labor often requires CAT ET for calibration and parameter programming.