SPN 108 - FMI 2 (Fault Code 295)
SPN 108 - FMI 2 (Fault Code: 295)
SPN108 FMI2
CODES:
Fault Code: 295
PID(P), SID(S): P108
SPN: 108
FMI: 2/2
Lamp: AMBER
SRT:
REASON: Barometric Pressure - Data Erratic, Intermittent, or Incorrect. The ambient air pressure sensor is reading an erratic value at initial key-on.
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| QSB3.3 ISBe, ISDe, ISC, ISL, and ISLe - Barometric Pressure Circuit |
Fault Code: 295
PID(P), SID(S): P108
SPN: 108
FMI: 2/2
Lamp: AMBER
SRT:
 |
| ISB - Barometric Pressure Sensor Circuit |
REASON: Barometric Pressure - Data Erratic, Intermittent, or Incorrect. The ambient air pressure sensor is reading an erratic value at initial key-on.
EFFECT: Engine power derate.
Circuit Description:
The ambient air pressure sensor responds to pressure changes in the atmospheric pressure. The pressure changes occur based on elevation where the engine is presently operating. The ambient air pressure sensor has a 5 volt supply circuit, a sensor signal voltage, and a return circuit.
The ambient air pressure sensor responds to pressure changes in the atmospheric pressure. The pressure changes occur based on elevation where the engine is presently operating. The ambient air pressure sensor has a 5 volt supply circuit, a sensor signal voltage, and a return circuit.
The engine control module
(ECM) provides a 5 volt supply to the ambient air pressure sensor on the
sensor supply 1 circuit.
The ECM also provides a ground on the
sensor return circuit. The ambient air pressure sensor provides a signal
to the ECM
on the ambient air pressure sensor signal
circuit. This sensor signal voltage changes, based on the pressure of
the atmosphere.
The ECM will detect a low signal voltage
when the vehicle is operating at high altitudes. The ECM will detect a
high signal
voltage when the vehicle is operating at
sea level altitudes.
Component Location:
Conditions for Running the Diagnostics:
-This diagnostic runs when the keyswitch is initially turned on before the engine is started.
-The diagnostic only runs once per trip when the keyswitch is initially turned on.
Conditions for Setting the Fault Codes:
The ECM detects that the ambient air pressure reading is higher or lower than the other absolute pressure sensors on the engine.
Action Taken When the Fault Code is Active:
• The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
• A default value of the ambient pressure reading is used.
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:
Possible causes of this fault code include:
• Stuck in-range barometric pressure sensor reading.
• High resistance in the barometric pressure sensor signal or return lines.
On ISB applications, this fault code will go active if the intake manifold pressure/temperature sensor is accidentally installed in the ambient air temperature/pressure sensor location. These sensors appear the same on the outside and can be accidentally interchanged.
Read More:
SPN 441 - FMI 4 (Fault Code 294)
SPN 441 - FMI 3 (Fault Code 293)
Blog.Teknisi
- ISB: The combination ambient air temperature/pressure sensor is located in the original equipment manufacturer (OEM) intake air plumbing.
- QSB3.3 ISBe, ISDe, ISC, ISL, and ISLe: The barometric pressure sensor is located near the intake manifold.
Conditions for Running the Diagnostics:
-This diagnostic runs when the keyswitch is initially turned on before the engine is started.
-The diagnostic only runs once per trip when the keyswitch is initially turned on.
Conditions for Setting the Fault Codes:
The ECM detects that the ambient air pressure reading is higher or lower than the other absolute pressure sensors on the engine.
Action Taken When the Fault Code is Active:
• The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
• A default value of the ambient pressure reading is used.
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 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.
- At key-on, before the engine starts, the sensor readings for intake manifold pressure, exhaust gas pressure, if equipped, and engine oil pressure, if equipped, are compared with the barometric pressure. This fault code occurs if the barometric pressure sensor reading is different from the other three. This check is only done once after the keyswitch is turned on.
Possible causes of this fault code include:
• Stuck in-range barometric pressure sensor reading.
• High resistance in the barometric pressure sensor signal or return lines.
On ISB applications, this fault code will go active if the intake manifold pressure/temperature sensor is accidentally installed in the ambient air temperature/pressure sensor location. These sensors appear the same on the outside and can be accidentally interchanged.
Read More:
SPN 441 - FMI 4 (Fault Code 294)
SPN 441 - FMI 3 (Fault Code 293)
Blog.Teknisi
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