SPN 1043 - FMI 4 (Fault Code 284)

SPN1043 FMI4
Engine Speed/Position Sensor (Crankshaft) Supply Voltage Circuit - Voltage below normal, or shorted to low source

Sensor Supply Voltage

Fault Code: 284
PID(P), SID(S): S221
SPN: 1043
FMI: 4/4
Lamp: Amber

REASON: Low voltage detected on the +5 volt sensor supply circuit to the engine speed sensor.

EFFECT: Engine may run rough, may stop running, may not start, or may be difficult to start.

Circuit Description:
The engine speed sensors are Hall effect type sensors. The engine control module (ECM) provides a 5 volt supply to the speed sensor and a return circuit. As the teeth on the crankshaft speed ring move past the speed sensor, a signal is generated on the speed sensor signal circuit. The ECM interprets this signal and converts it to an engine speed.

Component Location:
The engine speed sensor is located in the lower portion of the front cover on the intake side of the engine.

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 engine speed sensor supply voltage was out of range low.

Action Taken When the Fault Code is Active:
• The ECM illuminates the amber CHECK ENGINE lamp and/or the malfunction indicator lamp (MIL) immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault Code:
• To validate the repair, perform a key cycle, start the engine and let it idle 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:
• Tampering of the engine speed/position sensors.
-A damaged vehicle speed sensor.
-Look for intermittent engine harness connections in the primary engine speed sensor circuit.

Read More:
SPN 639 - FMI 9 (Fault Code 285)
SPN 639 - FMI 13 (Fault Code 286)


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