CAT 24 Fault Code: Oil Pressure voltage low
Oil Pressure voltage low · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 24, SPN 100 FMI 4, means the ECM has detected that the signal voltage from the engine oil pressure sensor has dropped below 0.2 VDC for more than eight seconds while the engine is running (or atmospheric pressure is above 80 kPa / 12 psi). It affects the C11, C13, C15, and C18 engines. It usually points to a wiring or connector problem, but it can also mean high crankcase pressure or a failing sensor, so it should not be ignored.
High severity. This code itself is a sensor circuit fault, not proof of an actual low oil pressure condition. But because it disables the ECM's real oil pressure reading, and one listed cause is a plugged crankcase breather that can lead to seal and ring failure, it should be diagnosed before continued heavy operation.
What does CAT error code 24 mean?
CAT fault code 24, SPN 100 FMI 4, is set when the Engine Control Module (ECM) sees the oil pressure sensor's signal voltage sitting too low for too long. The ECM constantly applies a pull-up voltage to the signal wire so it can watch for opens or shorts. When that voltage sags below 0.2 VDC for more than eight seconds, with the engine running or atmospheric pressure above 80 kPa (12 psi), and the ECM has been powered for at least two seconds, the code sets.
This is strictly a voltage-low diagnostic on the signal circuit. It does not necessarily mean the engine is truly low on oil pressure, it means the ECM cannot trust the signal it is getting from the sensor. That is important because when this code is active, the ECM may be running without a valid oil pressure input, which affects protection strategies and gauge readings.
Two related conditions are described for this code depending on when it triggers. One version applies when the engine is running or atmospheric pressure is above 80 kPa (12 psi); the ECM checks this alongside making sure the 168-01 low ECM battery power code and the 232-03/232-04 5-volt supply codes are not active.
What triggers a CAT 24 code?
The ECM sets this code when the oil pressure sensor signal voltage is less than 0.2 VDC for more than eight seconds, the ECM has been powered for at least two seconds, the 168-01 Low ECM Battery Power code is not active, the 232-03 and 232-04 5-volt supply codes are not active, and either the engine is running or atmospheric pressure is greater than 80 kPa (12 psi). Caterpillar Electronic Technician (ET) may take up to 30 seconds to display the code as active, so wait at least that long when checking.
Common causes of 24
- ECM connection or wiring harness problem, the most likely cause of this code
- Plugged crankcase breather causing excessive crankcase pressure, which can lead to crankshaft seal failure, then piston ring failure, and further increased crankcase pressure
- Failed or failing engine oil pressure sensor
- Damaged or corroded oil pressure sensor harness
- Sticking pistons, which can also produce this code; cylinder liners should be inspected for scoring or scuffing
- Failed ECM, listed as the least likely cause
How to troubleshoot CAT 24: first checks
- Wait at least 30 seconds after checking so Cat ET has time to display the code as active if it truly is active.
- Inspect the oil pressure sensor connector and wiring harness for corrosion, loose pins, or damage. This is the most likely cause according to Caterpillar.
- Check the crankcase breather for plugging or restriction, since excessive crankcase pressure is a listed cause and can lead to seal and ring damage if left unchecked.
- If the code is inactive but has occurred recently or frequently, clear the code, turn the key on, and gently wiggle the sensor and connector to try to reproduce it.
- If wiggling the connector does not reproduce the code, inspect for high crankcase pressure or a wiring problem, and inspect cylinder liners for scoring or scuffing if sticking pistons are suspected.
- Test the oil pressure sensor itself and its harness for continuity and correct signal voltage before condemning the ECM.
- Confirm that 168-01, 232-03, and 232-04 are not active, since any of these being active will block this code from a true low-oil-pressure diagnosis.
How the code clears
No separate clearing step is listed beyond normal diagnostic procedure. If the code is inactive but has happened recently or frequently, clear the code, turn the key on, and wiggle the sensor and connector to try to reproduce it. If the code does not come back, focus on checking for high crankcase pressure or a wiring problem instead of replacing parts.
Affected models and serial ranges
24 appears in our records across 4 CAT models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| C11 | Serial range not listed in source records |
| C13 | Serial range not listed in source records |
| C15 | Serial range not listed in source records |
| C18 | Serial range not listed in source records |
Frequently asked questions
What does CAT fault code 24 mean?
It means the ECM detected that the engine oil pressure sensor's signal voltage dropped below 0.2 VDC for more than eight seconds, which is SPN 100 FMI 4. It is a wiring or sensor circuit fault, not necessarily a true low oil pressure event.
Is CAT code 24 dangerous to keep running with?
It can be. The most likely cause is a wiring or connector problem, but one listed cause is a plugged crankcase breather, which raises crankcase pressure and can lead to crankshaft seal failure and then piston ring failure. Because the ECM's actual oil pressure signal is unreliable while this code is active, it should be diagnosed before continued operation.
Which CAT engines use this fault code?
This code applies to the C11, C13, C15, and C18 engines.
What is the most likely cause of code 24?
Caterpillar lists an ECM connection or wiring harness problem as the most likely cause. A failed ECM is listed as the least likely cause.
How do I try to reproduce an intermittent code 24?
If the code is inactive but has occurred recently or often, clear it, turn the key on, and wiggle the oil pressure sensor and its connector to try to trigger it again. If it does not reproduce, check for high crankcase pressure or a harness problem instead.
Why does the ECM wait 30 seconds to show this code as active?
Caterpillar notes there can be a delay of up to 30 seconds before Cat Electronic Technician (ET) displays an active diagnostic code, so technicians should wait at least that long before concluding a code is not active.
Can a plugged crankcase breather really cause an oil pressure sensor code?
Yes. A plugged breather increases crankcase pressure, which can damage the crankshaft seal, then the piston rings, which further raises crankcase pressure. This chain can affect the oil pressure sensor circuit and trigger this code.