Do not driveTo the nearest safe stop
SPN 26 is a manufacturer number outside the standard J1939 table: different makes can put different things under it. Below — how it is worded by Ford Trucks, Renault Trucks and ZF AS-Tronic, and what the second half of the code (FMI) means.
Ford TrucksRenault TrucksZF AS-Tronic
Ford Trucks/Ecotorq writes fault numbers in its own format: the code in the table below is a Ford code (hexadecimal, zero-padded), not a J1939 SPN. It matches the standard only where the signal itself is standard, and usually matches the title of this page by digit alone.
| FMI 0 | Urea Dosing System Pressure Compensation Error. FODP code (scan tool): P204B-32. |
| FMI 4 | Engine CAN bus fault. Repair: Run the diagnostic check of the EECU electronic unit. Check the parameters. Switch the ignition off, switch it on again and repeat the test. If the fault persists, replace the control unit. |
ZF AS-Tronic uses its own fault numbering: the number in the table below is an internal ZF code, not a J1939 SPN. It matches the title of this page by digit only and means something different.
| FMI 4 | CAN message timeout: "engine brake configuration" (engine configuration message). |
| SPN 26 FMI 026/0 · 26.0 | data above normal range (most severe level) |
| SPN 26 FMI 426/4 · 26.4 | voltage below normal or shorted to ground |
Do not drive. Stop as soon as it’s safe to do so — don’t keep going.
The code is flagged critical: the manufacturer considers it unsafe to keep driving without checking.
This code alone cannot say what will fail next, so stop at the first safe opportunity and look at it on the spot.
That said, the manufacturer flags this code as critical — if in doubt, it is safer to stop and check on the spot.
Scanner threw several codes at once? Paste the whole list — we will show which one is the root cause and which ones simply followed.