Safe to driveUntil the next service
J1939 code SPN 979. Below — how the fault is worded at the factory by Mercedes-Benz, and what the second half of the code (FMI) means in the standard.
| FMI 9 | J1939 PTO Message Not Received This Ignition Cycle |
| SPN 979 FMI 9979/9 · 979.9 | abnormal update rate |
Safe to drive. Below — how much time you have and what happens if you keep going.
A standalone fault with no immediate consequences for driving.
Show the codes at the next service. If a second code from the same system appears, stop putting it off.
Scanner threw several codes at once? Paste the whole list — we will show which one is the root cause and which ones simply followed.