PACCAR · sensor

SPN 102 FMI 3 — Boost pressure sensor circuit high

Derate possible, erratic power. Severity is rated warning with a amber lamp, shown on some service tools as P226C.

Written and reviewed by Christopher Scott Sneed, 30+ year diesel technician, founder of Blue Collar Empire.

What this code means

SPN 102 identifies the parameter the control module is monitoring — boost pressure sensor circuit high. FMI 3 is the failure mode the module logged against it. Both numbers matter: the same SPN with a different FMI is a different repair.

Symptoms you will see

Derate possible, erratic power.

Common causes

Chafed sensor harness
Soot-fouled boost sensor
Corroded connector pins

What to test first

Inspect the sensor connector for corrosion
Compare boost reading to barometric at key-on
Wiggle-test the harness while monitoring live data

Work the list in order and record the readings. Confirm the fault with live data before any part is ordered — a code names a circuit, never a failed component.

Is the truck safe to drive?

Generally safe to finish the trip

Safe to drive home at moderate speed. Book it in before your next loaded run.

Common mistakes on this code

Replacing the sensor named in the SPN before checking its wiring, connector and ground.
Clearing the code and handing the truck back without reproducing the operating condition that set it.
Reading one code out of a set instead of finding which fault occurred first.

When to get professional diagnosis

Get a shop involved when the fault comes with a red lamp or a shutdown timer, when the checks above all pass and the code returns, or when the repair needs an aftertreatment service tool, a forced regen, or engine internals. Nothing on this page is a substitute for OEM service literature or a qualified technician on the truck.

How Truck Commander helps

Enter this code in Blue Collar AI diagnostic support with the engine and the symptoms and you get the test sequence in order, per-truck history so repeat faults are visible, and a printable work order. Aftertreatment codes are covered in depth in the Aftertreatment Mastermind training. It is all in Truck Commander at $14.99 a month.