SPN 157 — Injector Metering Rail 1 Pressure (Fuel Rail)
System: Fuel
High-pressure fuel rail pressure on common-rail engines.
Can I keep running it?
HIGH — limit use, diagnose now
Rail pressure problems can cause stalling, no-start or severe derates. Avoid heavy work until fixed.
Likely causes
- Low fuel supply pressure (filters, lift pump, air)
- Worn high-pressure pump
- Leaking injector return or pressure relief valve
- Failed rail pressure sensor or wiring
- Fuel pressure regulator / inlet metering valve fault
Checks & fixes (easiest first)
- Start with fuel supply: filters, priming, air in fuel
- Compare desired vs. actual rail pressure on a scan tool
- Perform injector return flow test per OEM
- Inspect the rail pressure sensor connector
Common FMIs with SPN 157
- SPN 157 FMI 1Value too low (most severe)
- SPN 157 FMI 2Data erratic, intermittent, or incorrect
- SPN 157 FMI 3Voltage above normal or shorted high
- SPN 157 FMI 4Voltage below normal or shorted low
- SPN 157 FMI 16Value too high (moderately severe)
- SPN 157 FMI 18Value too low (moderately severe)
Related codes
FAQ
What does SPN 157 mean?
SPN 157 is Injector Metering Rail 1 Pressure (Fuel Rail). High-pressure fuel rail pressure on common-rail engines.
Can I keep running with SPN 157?
Rail pressure problems can cause stalling, no-start or severe derates. Avoid heavy work until fixed.
What causes SPN 157?
Low fuel supply pressure (filters, lift pump, air); Worn high-pressure pump; Leaking injector return or pressure relief valve; Failed rail pressure sensor or wiring; Fuel pressure regulator / inlet metering valve fault.