SPN 50 — Power Amp (Meritor (ex-WABCO) and ZF AS-Tronic)

Safe to driveDrivable, but watch it yourself

SPN 50 is a manufacturer number outside the standard J1939 table: different makes can put different things under it. Below — how it is worded by Meritor (ex-WABCO) and ZF AS-Tronic, and what the second half of the code (FMI) means.

Meritor (ex-WABCO)

FMI 3	Power Amp. Out Valve Left Rear — Shorted to Battery
FMI 5	Power Amp. Out Valve Left Rear — Open Circuit
FMI 6	Power Amp. Out Valve Left Rear — Short to Ground

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 10

Fault on valve Y17 output circuit (clutch slow release).

What FMI means in J1939

SPN 50 FMI 350/3 · 50.3	voltage above normal or shorted high
SPN 50 FMI 550/5 · 50.5	current below normal or open circuit
SPN 50 FMI 650/6 · 50.6	current above normal or grounded circuit
SPN 50 FMI 1050/10 · 50.10	abnormal rate of change

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: Drivable, but watch it yourself

This is an electrical fault: an open, a short or a bad contact in the sensor circuit. The value it measures is most likely fine.

You can drive. But until the circuit is repaired this system runs blind and cannot warn you about a real failure.

Nearby: other

• SPN 42
• SPN 43Power Amp
• SPN 44Power Amp
• SPN 45Power Amp
• SPN 49Power Amp
• SPN 56
• SPN 57Conditions for switching to reduced performance mode are faulty
• SPN 61PTO sensor fault
• SPN 62
• SPN 63PTO sensor fault

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