SPN 3511 - FMI 4 (Fault Code 238)

SPN 3511 - FMI 4 (Fault Code: 238)
SPN3511 FMI4
ISB, ISC, ISL with CM2150 - Engine Speed Sensor Supply 3 Circuit

Fault Code: 238
PID(P), SID(S): S232
SPN: 3511
FMI: 4/4

REASON : Sensor Supply 3 Circuit - Voltage Below Normal or Shorted to Low Source. Low voltage detected on the +5 volt sensor supply circuit to the engine speed sensor.

EFFECT : Possible hard starting and rough running.

Circuit Description:
The sensor supply 3 circuit provides 5 volt supply to the primary engine speed/position sensor.

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 electronic control module (ECM) detects that the sensor supply 3 signal voltage is less than 4.75-VDC for more than 1 second.

Action Taken When the Fault Code is Active:
• The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
• The backup engine speed sensor will be used by the ECM for the engine speed signal.

Conditions for Clearing the Fault Code:
The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes.

Shop Talk:

  • Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe® Online for applicable fixes to the calibration stored in the ECM. If necessary, recalibrate the ECM.
  • The ECM monitors the voltage level on the engine speed sensor +5 volt supply circuit. If the voltage falls below a limit which can be calibrated, then this fault is recorded.
  • Possible causes of this fault code are a short circuit to ground in the engine harness, sensor, or ECM.

Read More:
SPN 108 - FMI 4 (Fault Code 222)
SPN 108 - FMI 3 (Fault Code 221)


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