Fuel Rail Pressure Sensor Circuit Low
The DD-157-4 (Detroit Diesel DD Series) diesel fault code means: Fuel Rail Pressure Sensor Circuit Low. This is a moderate severity code.
This is a standard J1939 fault, not a proprietary code. DD-157-4 is how this equipment displays SPN 157 with FMI 4 (voltage below normal or shorted low) under the SAE J1939 standard used across heavy equipment. The same SPN can appear on any J1939-compliant machine regardless of brand — so cross-referencing it against your engine maker's documentation is valid even when the equipment brand differs.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- intermediate
- Estimated cost
- $500-$2,200
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What Are the Symptoms of DD-157-4?
- Check Engine Light / Amber Warning Lamp illuminated
- Hard starting or extended crank
What Causes DD-157-4? (Most Likely First)
- Failed rail pressure sensor Likely
- Open 5V reference to sensor Likely
- Short to ground on signal wire Possible
Can I Still Drive with DD-157-4?
Yes, but fix soon. DD-157-4 is rated moderate severity. It is not an immediate stop-driving fault, but it will not clear itself — book the repair rather than ignoring it.
Frequently Asked Questions
What is Detroit Diesel fault code DD-157-4?
Detroit Diesel fault DD-157-4 (SPN 157 FMI 4) indicates: Fuel Rail Pressure Sensor Circuit Low. It is a moderate-severity fault and is commonly seen on DD13/DD15/DD16 engines in Freightliner and Western Star chassis.
Can I drive my Freightliner or Western Star with fault DD-157-4?
It depends on severity. Critical and serious faults trigger derate or engine shutdown — do not continue driving. Moderate faults usually allow continued operation short-term but schedule repair to prevent cascading aftertreatment damage.
How much does it cost to fix Detroit Diesel fault DD-157-4?
Estimated repair cost is $500-$2,200. Sensor/harness fixes fall at the low end; turbo actuator, injector, aftertreatment component, or head gasket repairs fall at the high end. Detroit DDDL software and sometimes factory parameter reset are required for proper reset.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose DD-157-4?
Back-probe rail pressure sensor — expect ~0.5V engine off.
Check 5V reference at sensor connector key-on.
Replace sensor (mounted on rail); torque to spec or leaks result.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- Perkins 854F-34T Engine Fault Code table, printed in the Genie S-100/S-105/S-120/S-125 Service Manual, Part No. 102916, January 2016printed page 5-29: SPN 157 FMI 4, "Engine Injector Metering Rail#1 Pressure: Voltage Below Normal". The table is that engine maker's; it establishes what the J1939 SPN-FMI pair means, not that a Detroit Diesel display shows it.
Which Vehicles Commonly Get DD-157-4?
- Freightliner Cascadia with DD15
- Freightliner Cascadia with DD13
- Freightliner Cascadia with DD16
- Western Star 4700 with DD13/DD15
- Western Star 4900 with DD15/DD16
- Western Star 5700 XE with DD15
- Freightliner M2 106 with DD13
- Freightliner M2 112 with DD13
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