CAT Engine E272 Fault Code: Inlet Air Restriction Warning
Also called High Inlet Air Temperature Warning
Inlet Air Restriction Warning · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
E272 covers two related warnings on CAT C12, C15, C16, and C27 engines (and older 3176C, 3196, 3406E): high air inlet temperature or restricted inlet air flow to the turbocharger(s). The ECM logs the event, warns the operator in the cab, and on some engines derates power by up to 15 percent.
Medium severity. E272 is a warning code, not an immediate shutdown. Engines may run derated with low power until the underlying restriction or temperature issue is fixed. Continuing to run with a plugged filter or overheating charge air can cause turbocharger or aftercooler damage over time, so it should be diagnosed the same shift it appears.
What does CAT Engine error code E272 mean?
E272 is triggered by the ECM when it sees either an inlet air temperature that is too high, or an inlet air restriction that is too great, on the turbocharger intake side. Both conditions point to the engine not getting clean, cool air the way it should, which hurts combustion efficiency and can push heat and stress into the turbo and aftercooler.
On 3176C and 3196 engines, the warning fires when inlet air temperature climbs above 79 °C (174 °F) for more than 4 seconds, after the engine has run more than 3 minutes past reaching within 50 rpm of low idle. On the 3406E, the same logic applies but the threshold is lower, at 75 °C (167 °F) for more than 4 seconds.
The restriction side of E272 is set when the ECM calculates inlet air restriction (the difference between atmospheric pressure and turbo inlet pressure) and finds it too high, typically caused by a plugged air filter. On engines with the restriction logic, this can trigger a 15 percent power derate until the ECM is powered down and the condition clears.
What triggers a CAT Engine E272 code?
Temperature version (3176C/3196): inlet air temperature above 79 °C (174 °F) for more than 4 seconds, only after the engine has run more than 3 minutes since reaching within 50 rpm of low idle. Temperature version (3406E): inlet air temperature above 75 °C (167 °F) for more than 4 seconds, same 3-minute run and 50-rpm idle condition. Restriction version: inlet air restriction of at least 9 kPa (36 inches of H2O) in either the right or left turbocharger. A related variant sets when restriction exceeds 8.5 kPa (34 inches of H2O) for 30 seconds. Another related variant sets when air inlet pressure for the left or right turbocharger is above a default value of 7 kPa (28 inches of H2O) for 5 seconds. All versions require that related sensor circuit faults (172-03, 172-04, 274-03, 274-04, 275-03, 275-04, 276-03, 276-04) are not active at the same time.
Common causes of E272
- Restricted or plugged air filter, which is the most common cause of inlet air restriction on these engines.
- A problem with the air inlet system generally, such as a collapsed hose, blocked intake ducting, or damaged charge piping.
- A problem with one of the air inlet pressure sensors (atmospheric pressure sensor, right turbo inlet pressure sensor, or left turbo inlet pressure sensor).
- A problem with the aftercooler, listed specifically as a possible cause of the high inlet air temperature version on 3406E engines.
- A problem with the air inlet temperature sensor itself, also listed for the 3406E high-temperature version.
How to troubleshoot CAT Engine E272: first checks
- Check the air filter and air filter housing for restriction, dirt loading, or damage. A plugged filter is the single most common cause of this code.
- Inspect intake ducting, hoses, and clamps between the air filter, turbocharger inlet, and aftercooler for collapse, cracks, or blockage.
- Verify the related sensor circuits (atmospheric pressure sensor, right and left turbo inlet pressure sensors, intake manifold air temperature sensor) are wired correctly and free of corrosion, since open or short circuit faults on these sensors will block E272 from setting correctly and point to a wiring problem instead.
- On engines showing the high-temperature version, inspect the aftercooler core for plugging, damage, or reduced cooling airflow.
- Confirm engine idle and run time conditions were actually met before assuming a sensor fault; the temperature version only sets after several minutes of run time near low idle rpm.
How the code clears
For the high inlet air temperature version, the ECM automatically resets the warning once inlet air temperature drops below the reset threshold: 77 °C (171 °F) for more than 2 seconds on 3176C/3196 engines, or 73 °C (163 °F) for more than 4 seconds on 3406E engines. For the inlet air restriction version, the warning stays active until the ECM is powered down, even if the restriction clears, so a key cycle after repair is needed. No separate manual reset procedure is listed for either version beyond fixing the root cause and, where applicable, cycling ECM power.
Affected models and serial ranges
E272 appears in our records across 4 CAT Engine models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| C12 | Serial range not listed in source records |
| C15 | Serial range not listed in source records |
| C16 | Serial range not listed in source records |
| C27 | Serial range not listed in source records |
Frequently asked questions
What does CAT fault code E272 mean?
E272 means the ECM has detected either high inlet air temperature or high inlet air restriction on the turbocharger air intake side. It is a warning code that can come with reduced engine power.
Will E272 cause a derate or shutdown?
E272 does not shut the engine down, but on engines with the restriction logic the ECM can derate power by up to 15 percent while the fault is active. Other versions log a low power warning without a stated derate percentage.
What is the most likely cause of E272?
A plugged or heavily restricted air filter is the most common cause. Damaged intake ducting, a failing aftercooler, or a faulty inlet air pressure or temperature sensor are also listed possibilities.
How do I clear an E272 code?
For the high temperature version, the ECM clears the warning automatically once inlet air temperature drops back below the reset threshold for the required time. For the restriction version, the warning remains active until the ECM is powered down, so you typically need to fix the cause and cycle the key.
Which engines can show code E272?
E272 appears on CAT C12, C15, C16, and C27 engines, as well as the older 3176C, 3196, and 3406E engines, though the exact temperature and restriction thresholds differ by engine family.
Can a bad sensor cause a false E272?
Yes. The ECM checks that related sensor circuits are not showing an open, short to battery, or short to ground fault before it will set E272. If one of those sensor circuits is faulty, you should see a separate diagnostic code for that circuit, and it should be repaired first since it can affect the readings E272 relies on.