What This Sensor Does
The barometric pressure sensor reads atmospheric pressure and temperature and reports both to the ECM. The ECM uses that signal to correct fuel quantity, injection timing, and boost targets as air density changes with altitude and weather. Without a usable baro reference the ECM has no way to tell dense sea-level air from thin mountain air, so it falls back to a default value.
That default is conservative. On a failed or drifting sensor you typically see reduced power, a soft derate, black smoke or poor fuel economy that follows elevation changes rather than load. Trucks that run the mountains and then park in the valley tend to surface the fault first, because the sensor is being asked to swing across the widest part of its range.
The sensor is a sealed unit with the sensing element, connector, and housing as one assembly. It is not serviceable. When the element drifts, the internal reference leaks, or moisture gets past the connector seal, the whole sensor gets replaced. This aftermarket part is a direct replacement that mounts in the factory location with no modification.
Why These Numbers Cross
4902720, 3085140 and 4359572 are Cummins numbers covering the same barometric/ambient pressure sensing function across the ISX, ISX15, ISM, L10 and M11 families. Numbers get superseded over a long production run for supplier changes, connector revisions, and calibration housekeeping, not because the part does a different job. The sensing range, mounting, and electrical interface stay compatible, so one physical sensor covers the group.
Older L10 and M11 builds are the ones most likely to show the earlier numbers on the tag, while ISX and ISM service records tend to list 4902720. If the number on your old sensor is one of the three above, you are looking at the same part. Those numbers are listed here for identification only — PartStop is not affiliated with, endorsed by, or authorized by any OEM.
Cross-reference is where you start, not where you finish. Pull the old sensor, read the number stamped or printed on the body, and check your engine serial number. The same engine model can carry different sensor calibrations depending on build date and emissions configuration, so confirm by ESN or by the number on the part you removed before ordering.
Check Before You Swap
Before condemning the sensor, check the connector and harness. These sensors sit in under-hood heat and vibration, and the failure is often a green pin, a chafed wire, or water in the connector body rather than a bad element. Backprobe for the reference voltage and a clean ground with the key on. Wiggle-test the harness while watching live data for signal dropouts.
Compare the baro reading against a known local barometric pressure and against the intake manifold pressure sensor with the engine off. Key on, engine off, both should read close to atmospheric. A baro sensor that is offset several psi from ambient, or one that will not track when you change elevation, is done. Torque the replacement to spec and reseat the connector fully — an unlatched connector will put you right back where you started.
4902720 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to 4902720. Use them to identify the part — then confirm the exact fit by VIN or the number stamped on your old unit before you order. An interchange is a starting point, not a fitment guarantee.
| Brand / Line | Cross-Reference Numbers |
|---|---|
| Cummins | 3085140, 4359572 |
Frequently asked questions
Will a bad barometric pressure sensor cause a derate?
It can. When the ECM loses a usable ambient pressure signal it substitutes a default value and pulls fuel back to stay out of trouble, which shows up as reduced power or a soft derate. You may also see smoke or poor economy that changes with elevation. Clear the code, verify the reading against local barometric pressure, and check the harness before replacing anything.
Is 3085140 the same sensor as 4902720?
3085140 and 4359572 both cross to 4902720 for this barometric/ambient pressure sensing application on ISX, ISX15, ISM, L10 and M11 engines. The numbers reflect supersessions over a long production run rather than a different function. Confirm by reading the number on the sensor you pulled and by your engine serial number — cross-reference is a starting point, not a fitment guarantee.
Where is the baro sensor located on an ISX?
This is a direct replacement that installs in the factory location with no modification, so it goes back exactly where the old one came out. Locations vary by build and chassis, so trace the harness from the connector on the old sensor rather than guessing. Note the orientation and connector routing before you remove it.
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More cross-reference guides
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