SPN 1231
CAUTION
J1939-1 datalink
The truck's control module (ECU) reports a fault on: J1939-1 datalink.
SPN 1231 means a truck control module (ECU) flagged a fault on J1939-1 datalink, part of the Electrical / J1939 system on heavy-duty diesel trucks. DERATE rates it CAUTION: you can keep driving carefully, but get it checked soon. Part usually replaced: J1939 datalink repair (connector / terminating resistor), $20–$350 (aftermarket to dealer) plus 1–3 h labor.
Electrical / J1939
Can I keep driving?
Yes, carefully. It does not usually cut power, but get it checked soon.
Part usually replaced
J1939 datalink repair (connector / terminating resistor)
$20–$350 (aftermarket to dealer)
Labor: 1–3 h
USD, part only. Labor is billed at the shop's hourly rate.
Data: DERATE verified base, updated October 2026
Related codes
Read it off your own dash
Take one photo and DERATE tells you whether you can keep driving.
Ask DERATE
DERATE assists. It does not replace inspection by a qualified technician.