SAE J1939 Data Link - Unable To Transmit
The CUMMINS-426 (Cummins) diesel fault code means: SAE J1939 Data Link - Unable To Transmit. This is a moderate severity code.
Unverified. We could not confirm this code's definition against freely available manufacturer documentation, so treat the meaning, severity and fix guidance on this page as unconfirmed. Check it against the manufacturer's service information for your exact model and serial range before acting on it. This page is kept out of search engines for that reason, and we are working through this family manual by manual.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- advanced
- Estimated cost
- $200-$900
Down with a Cummins fault on the road?
We are building a network of verified mobile diesel and reefer technicians along the freight corridor. It is not live yet — no one can be dispatched to you today. You can see where the pilot is launching and register interest.
View pilot availability →What Are the Symptoms of CUMMINS-426?
- Multiple warning lights illuminated
- Intermittent sensor faults
- Erratic dash gauge behavior
- Possible engine stall
- Battery or charging system warnings
What Causes CUMMINS-426? (Most Likely First)
- Sensor supply (5V reference) circuit fault Very Likely
- Harness chafing causing short or open Likely
- Loose or corroded ground connection Likely
- Multiple sensors drawing on same supply overloaded Possible
- ECM internal supply driver failure Less Likely
Can I Still Drive with CUMMINS-426?
Yes, but fix soon. CUMMINS-426 is rated moderate severity. It is not an immediate stop-driving fault, but it will not clear itself — book the repair rather than ignoring it.
Frequently Asked Questions
What is Cummins fault code 426?
Cummins fault code 426 indicates: SAE J1939 Data Link - Unable To Transmit. It is a moderate-severity fault affecting engine electrical supply or communications.
Can I drive with Cummins fault code 426?
Yes, short-term driving is typically safe with fault 426, but the fault will illuminate the Check Engine Light and must be diagnosed soon. Monitor for power loss, unusual noises, or gauge changes and pull over if conditions worsen.
How much does it cost to fix Cummins fault 426?
Repair cost is approximately $200-$900 including parts, labor, and any dealer programming required. DIY repairs (sensor replacement) fall at the low end; pump, aftertreatment, or ECM work falls at the high end and usually requires INSITE diagnostic software.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose CUMMINS-426?
Connect INSITE and read all active codes related to fault 426 -- multiple sensor faults on one supply indicate a supply fault.
Measure 5V reference supply voltage at ECM pin and at the sensor connector; must be 4.9-5.1V stable.
Unplug sensors one at a time while watching live data to find a sensor pulling the supply low.
Inspect harness for chafing where it crosses the engine or frame; look for green or bright corrosion at connectors.
Verify battery voltage and alternator output are within spec (13.8-14.4V engine running).
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J1939-73Application Layer: Diagnostics (defines the SPN/FMI fault-identifier framework)
Which Vehicles Commonly Get CUMMINS-426?
- Peterbilt 579, 567 with Cummins ISX/X15
- Kenworth T680, T880 with Cummins X15
- Ram 2500/3500 with 6.7L Cummins
- Ram 4500/5500 with 6.7L Cummins
- Freightliner M2 106 with Cummins ISL9/L9
Explore More
Was this helpful?
Send this to whoever is fixing the truck — your tech, or the person asking what the fault means.