CAT Engine 944 Fault Code: Fuel Pressure short to ground
Also called Fuel Delivery Pressure Sensor : Voltage Below Normal, Fuel Pressure Short to Ground
Fuel Pressure short to ground · ai-assisted, editor-reviewed · Last updated 2026-07-21
TL;DR
Code 944 sets when the ECM sees fuel delivery pressure sensor signal voltage that is below normal, indicating a short to ground, open circuit, or wiring fault on the fuel pressure signal circuit. The ECM logs the code, flags fuel pressure as invalid, and substitutes a default gauge pressure of zero. Caterpillar states there are no performance effects from this fault by itself, but a bad reading can mask a real fuel supply problem.
Medium severity. The ECM reports no performance effects from this code alone since it substitutes a default value for the invalid signal, so the engine keeps running. Diagnose it within the shift because it removes real fuel pressure monitoring, and an actual low fuel pressure condition could go undetected while this code is active.
What does CAT Engine error code 944 mean?
Code 944 is set on the C10 through C32 engine family when the ECM detects that the signal voltage from the fuel delivery pressure sensor is below the normal range it expects. This is a low-signal or open-circuit fault, not a high-voltage fault. The ECM treats the reading as invalid rather than trusting a false low pressure value.
When this happens, the ECM logs the code and substitutes a default gauge pressure value of zero for fuel delivery pressure. Caterpillar's documentation for this code states there are no performance effects tied to the fault itself, meaning the engine will not automatically derate or shut down because of this code alone.
The bigger concern is diagnostic blindness: with the sensor signal flagged invalid, the ECM cannot use real fuel pressure data for other monitoring or control decisions, so any actual fuel delivery problem happening at the same time will not be visible through this sensor's reading.
What triggers a CAT Engine 944 code?
The ECM detects signal voltage below normal on the fuel delivery pressure sensor circuit for eight seconds, after the ECM has already been powered for two seconds.
Common causes of 944
- Damaged, corroded, or disconnected connectors on the fuel pressure sensor circuit
- Chafed, pinched, or abraded wiring in the harness between the ECM and the sensor
- An open circuit or excessive resistance in the harness between the ECM and the sensor
- The signal wire shorted to ground somewhere in the harness
- Seals out of place at the sensor connector allowing moisture intrusion
- A faulty or failed fuel delivery pressure sensor
- An intermittent connection issue that only shows the fault under vibration or temperature changes
- A faulty ECM that is not reading the signal correctly or not producing correct supply voltage to the sensor
How to troubleshoot CAT Engine 944: first checks
- Inspect the fuel delivery pressure sensor connector for corrosion, moisture, bent pins, or a loose fit, and confirm any seals are seated properly
- Trace the harness from the sensor back to the ECM looking for chafe points, pinches, or abrasion against other components or brackets
- With the connector disconnected, check the signal wire for continuity and for an unwanted short to ground or chassis
- Check the sensor supply voltage and ground reference at the sensor connector to confirm the ECM is providing correct power to the sensor
- Wiggle-test the harness and connector while monitoring the signal for intermittent dropouts, since several listed causes point to intermittent wiring issues
- If wiring and connectors check out, swap or bench test the fuel delivery pressure sensor before condemning the ECM
How the code clears
No separate clearing step is listed. Once the wiring, connector, or sensor fault causing the low signal voltage is repaired, the ECM should read valid fuel pressure signal voltage again and the code should stop logging on its own. Confirm the fix by clearing the logged code with diagnostic software and verifying it does not return during a test run.
Affected models and serial ranges
944 appears in our records across 8 CAT Engine models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| C10 | Serial range not listed in source records |
| C11 | Serial range not listed in source records |
| C12 | Serial range not listed in source records |
| C13 | 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 |
| C32 | Serial range not listed in source records |
Frequently asked questions
What does CAT code 944 mean?
It means the ECM is reading fuel delivery pressure sensor signal voltage that is below normal, so it treats the pressure reading as invalid and substitutes a default value of zero gauge pressure until the underlying wiring or sensor fault is fixed.
Will code 944 cause a derate or shutdown?
Caterpillar's documentation for this code states there are no performance effects from the fault itself. The ECM logs the code and uses a default value, but does not describe a derate or shutdown tied specifically to 944.
What is the most common cause of code 944?
Wiring and connector problems are the most frequently listed cause across the documented versions of this code, including damaged connectors, harness chafing, corrosion, seals out of place, and open or grounded signal wires. A faulty sensor or ECM is possible but listed after wiring issues.
How is code 944 different from code 943?
Code 943 covers the fuel pressure signal being open or shorted to battery voltage, a high-signal condition. Code 944 covers the opposite failure mode, a signal voltage that reads below normal, typically from an open circuit, grounded signal wire, or lost sensor supply. If your signal is reading unexpectedly high instead of low or missing, check the 943 page instead.
Can I keep operating the machine with code 944 active?
Since Caterpillar lists no performance effects from this code alone, the engine will typically keep running, but treat the missing fuel pressure data as a blind spot. Get it diagnosed within the shift rather than running indefinitely, since a real fuel delivery problem could be hidden while this sensor reads invalid.
Does code 944 require replacing the fuel pressure sensor?
Not necessarily. Check connectors, harness wiring, and the sensor supply voltage first, since wiring and connector issues are listed more often than sensor failure. Replace the sensor only after wiring and connections check out, and consider the ECM only as a last resort.