What does SPN 158 FMI 0 (158/0) mean?

Battery Voltage At Ignition Switch: data above normal range (most severe level).

What does SPN 158 FMI 1 (158/1) mean?

Battery Voltage At Ignition Switch: data below normal range (most severe level).

SPN 158 — Battery Voltage At Ignition Switch

Q: Can I keep driving with code SPN 158 (Battery Voltage At Ignition Switch)?

Safe to drive. Below — how much time you have and what happens if you keep going.

Safe to driveTo the nearest safe stop

J1939 code SPN 158. Below — how the fault is worded at the factory by International, KAMAZ, MAZ, Renault Trucks, YaMZ and ZF AS-Tronic, and what the second half of the code (FMI) means in the standard.

International KAMAZ MAZ Renault Trucks YaMZ ZF AS-Tronic

International

FMI 2

Battery Potential (Voltage), Switched — Key State Ignition Signal Error

KAMAZ

FMI 0	Switched battery voltage (terminal 15). K-line code on KamAZ-5490: ADM3 11100.
FMI 1	Switched battery voltage (terminal 15). K-line code on KamAZ-5490: ADM3 11101.
FMI 2	Switched battery voltage (terminal 15). K-line code on KamAZ-5490: MR2 12219.
FMI 12	No signal from terminal 15 (ignition)
FMI 14	Switched battery voltage (terminal 15). K-line code on KamAZ-5490: MR2 12319.

MAZ

FMI 12

Terminal 15 circuit fault - No terminal 15 signal at ECU startup. Blink code: 1-2-3. Repair: Check terminal 15 and its wiring.

Renault Trucks

FMI 0

Shift cylinder sensor exceeds the allowed limits. Repair: Switch the ignition off, switch it on again and repeat the test. If the fault persists, replace the control unit.

YaMZ

FMI 12

Terminal 15 circuit fault (No T15 signal during ECU initialization). Blink code: 1-2-3. Repair: Check terminal 15 and its wiring.

ZF AS-Tronic

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 0

Main gear engagement sensor signal stays in the position selected by the driver.

What FMI means in J1939

SPN 158 FMI 0158/0 · 158.0	data above normal range (most severe level)
SPN 158 FMI 1158/1 · 158.1	data below normal range (most severe level)
SPN 158 FMI 2158/2 · 158.2	data erratic or intermittent
SPN 158 FMI 12158/12 · 158.12	faulty device or component
SPN 158 FMI 14158/14 · 158.14	manufacturer-specific instructions

Can I keep driving

Safe to drive. Below — how much time you have and what happens if you keep going.

What happens if you keep driving

Time you have: To the nearest safe stop

The electrical system is not holding voltage. While the engine runs the alternator carries it; shut it off and you may not restart.

Next the lights go, then modules start dropping out and false codes appear all over the truck. Get to somewhere with help without shutting the engine down.

That said, the manufacturer flags this code as critical — if in doubt, it is safer to stop and check on the spot.

What to check on the spot

Check the battery terminals and earth strap — corrosion and loose clamps throw false codes all over the truck. Running voltage should be 27–29 V.

Nearby: power supply

Scanner threw several codes at once? Paste the whole list — we will show which one is the root cause and which ones simply followed.