Boost Pressure Sensor
Location, connector pinout, test procedure, and related fault codes for the turbocharger boost pressure sensor on Class 8 diesel trucks.
Last updated: 2026-09-20
Overview
The boost pressure sensor measures turbocharger outlet pressure in the intake system. The ECM uses this reading for VGT vane position control, fueling calculations, and derate protection. A failed boost sensor causes the ECM to run open-loop turbo control, resulting in low power, black smoke, or derate.
Sensor Locations by Platform
Cummins X15
Mounted on intake manifold near charge air cooler outlet, driver side.
X15 may use a combined MAP/boost sensor — verify SPN before replacing.
PACCAR MX-13
Located near turbo outlet on intake manifold, driver side.
MX-13 boost sensor connector is prone to moisture ingestion.
Detroit DD15
Mounted near charge air cooler outlet on intake manifold.
DD15 boost sensor port can plug with EGR soot — clean port during replacement.
Volvo/Mack MP8
Located on intake manifold near throttle plate, passenger side.
MP8 boost sensor is separate from MAP sensor on most configurations.
DieselVision™ identifies sensor labels and connector pin numbers — upload a close-up photo and the system maps pins automatically.
Connector Pinout
| Pin | Function | Specification |
|---|---|---|
| A | 5V Reference | 4.75–5.25V |
| B | Ground (Signal Return) | <0.1V to chassis ground |
| C | Signal Output | 0.5V at 0 PSI, ~2.0V at atmospheric, 4.5V at max boost |
Test Procedure
Read boost pressure live data at key on, engine off
Expected: ~14.7 PSI (atmospheric). Varies with altitude.
Tool: OEM diagnostic software
Measure 5V reference voltage at harness connector
Expected: 4.75–5.25V between pin A and pin B
Tool: Multimeter
Check ground circuit resistance from pin B to chassis ground
Expected: <0.5 ohms
Tool: Multimeter
Check signal wire for short to ground (sensor disconnected, key off)
Expected: >1 MΩ between pin C and chassis ground
Tool: Multimeter
Start engine and monitor boost pressure under load
Expected: Boost increases with load. At rated power: 25–45 PSI depending on engine
Tool: OEM diagnostic software
Common Failure Modes
- •Internal sensor failure — signal stuck high or low
- •Connector corrosion causing intermittent signal
- •Signal wire short to ground (FMI 4)
- •Signal wire short to voltage (FMI 3)
- •Open circuit in signal wire
- •Sensor port plugged with oil mist
Frequently Asked Questions
Where is the boost pressure sensor located on a diesel engine?
The boost pressure sensor is mounted on the intake manifold, typically near the charge air cooler outlet on the driver side of the engine.
What voltage should a boost sensor read at key on, engine off?
At key on, engine off, the boost sensor should read approximately 14.7 PSI (atmospheric pressure), which corresponds to roughly 1.5–2.0V signal output.
What fault codes are caused by a failed boost sensor?
Common fault codes include SPN 106 FMI 3 (voltage above normal), SPN 106 FMI 4 (voltage below normal), and SPN 102 FMI 16 (boost pressure above normal).
What is the difference between a MAP sensor and a boost sensor?
On many engines they are the same sensor — the MAP sensor measures manifold absolute pressure which includes boost. Some engines have separate sensors for pre-turbo and post-turbo pressure.
Snap a photo of your scan tool screen and let Diesel Vision interpret the fault instantly — no manual code lookup required.
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