SPN 94 - FMI 4 (Fault Code 547)
Wednesday, July 04, 2018
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SPN94 FMI4
Fuel Delivery Pressure Sensor Circuit - Voltage Below Normal or Shorted to Low Source
CODES:
Fault Code: 547
PID(P), SID(S): P94
SPN: 94
FMI: 4/4
Lamp: Amber
REASON: Low signal voltage detected at the fuel rail pressure sensor circuit.
EFFECT: Engine may run rough, may stop running, may not start, or may be difficult to start.
Circuit Description:
The engine control module (ECM) provides a 5 volt supply and ground to the fuel rail pressure sensor using a dedicated sensor supply circuit. The pressure sensor delivers a fuel pressure signal to the ECM of the fuel rail. During engine operating conditions, the ECM commands and monitors the fuel rail pressure. If the fuel rail pressure exceeds or falls below commanded pressure, a fault will set.
Component Location:
The rail fuel pressure sensor is located on the bottom front corner of the integrated fuel system module (IFSM).
Conditions for Running the Diagnostics:
This diagnostic runs continuously when the keyswitch is in the ON position or when the engine is running.
Conditions for Setting the Fault Codes:
The Engine Control Module (ECM) detected the fuel rail pressure signal voltage was out of range low.
Action Taken When the Fault Code is Active:
• The ECM illuminates the amber CHECK ENGINE lamp immediately when the diagnostic runs and fails.
-A default value for the fuel rail pressure reading is used.
Conditions for Clearing the Fault Code:
• To validate the repair, perform a key cycle, and leave the key in the ON position for 1 minute.
• The fault code status displayed by the recommended Cummins® electronic service tool or equivalent will change to INACTIVE immediately after the diagnostic runs and passes.
• The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
• The “Reset All Faults” command in the recommended Cummins® electronic service tool or equivalent can be used to clear active and inactive faults.
Shop Talk:
Possible causes of this fault code include:
Signal circuit open or shorted to ground in the engine harness or sensor.
• Supply wire open or shorted to ground.
• A malfunctioning fuel rail pressure sensor
Read More:
SPN 558 - FMI 4 (Fault Code 551)
SPN 157 - FMI 16 (Fault Code 553)
Blog.Teknisi
Fuel Delivery Pressure Sensor Circuit - Voltage Below Normal or Shorted to Low Source
 |
| Fuel Rail Pressure Sensor Circuit |
CODES:
Fault Code: 547
PID(P), SID(S): P94
SPN: 94
FMI: 4/4
Lamp: Amber
REASON: Low signal voltage detected at the fuel rail pressure sensor circuit.
EFFECT: Engine may run rough, may stop running, may not start, or may be difficult to start.
Circuit Description:
The engine control module (ECM) provides a 5 volt supply and ground to the fuel rail pressure sensor using a dedicated sensor supply circuit. The pressure sensor delivers a fuel pressure signal to the ECM of the fuel rail. During engine operating conditions, the ECM commands and monitors the fuel rail pressure. If the fuel rail pressure exceeds or falls below commanded pressure, a fault will set.
Component Location:
The rail fuel pressure sensor is located on the bottom front corner of the integrated fuel system module (IFSM).
Conditions for Running the Diagnostics:
This diagnostic runs continuously when the keyswitch is in the ON position or when the engine is running.
Conditions for Setting the Fault Codes:
The Engine Control Module (ECM) detected the fuel rail pressure signal voltage was out of range low.
Action Taken When the Fault Code is Active:
• The ECM illuminates the amber CHECK ENGINE lamp immediately when the diagnostic runs and fails.
-A default value for the fuel rail pressure reading is used.
Conditions for Clearing the Fault Code:
• To validate the repair, perform a key cycle, and leave the key in the ON position for 1 minute.
• The fault code status displayed by the recommended Cummins® electronic service tool or equivalent will change to INACTIVE immediately after the diagnostic runs and passes.
• The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
• The “Reset All Faults” command in the recommended Cummins® electronic service tool or equivalent can be used to clear active and inactive faults.
Shop Talk:
Possible causes of this fault code include:
Signal circuit open or shorted to ground in the engine harness or sensor.
• Supply wire open or shorted to ground.
• A malfunctioning fuel rail pressure sensor
Read More:
SPN 558 - FMI 4 (Fault Code 551)
SPN 157 - FMI 16 (Fault Code 553)
Blog.Teknisi
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