CAT Engine 943 Fault Code: Fuel Pressure open/short to +batt
Also called Fuel Delivery Pressure Sensor : Voltage Above Normal, Fuel Pressure Open/Short to +Batt, Fuel Pressure Open/Short to +batt
Fuel Pressure open/short to +batt · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 943 (SPN 94 / FMI 3) means the ECM is reading a fuel delivery pressure signal voltage that is above normal. The ECM logs the code, flags the fuel pressure reading as invalid, and substitutes a default value. There are no performance effects reported for this specific condition, but the underlying wiring or sensor issue should still be checked.
Medium severity. CAT states there are no performance effects from this code, since the ECM simply substitutes a default fuel pressure value. It is not an emergency shutdown code, but the sensor circuit should be diagnosed within the shift since fuel pressure data is being ignored by the engine controls.
What does CAT Engine error code 943 mean?
Code 943 is set when the CAT ECM sees a signal voltage from the fuel delivery pressure sensor that reads above the normal expected range. This is an electrical/signal fault on the sensor circuit rather than an actual fuel system pressure problem.
When this happens, the ECM logs the code, flags the fuel pressure reading as invalid data, and substitutes a default value in its place. On some ECM/sensor configurations a warning light will illuminate if the machine is equipped with one. CAT notes there are no performance effects tied to this specific fault, meaning the engine should continue to run using the default fuel pressure value.
This code is distinct from throttle position sensor faults described in some CAT diagnostic manuals under similar numbering; 943 as documented here is specifically about the fuel delivery pressure sensor signal circuit.
Common causes of 943
- Damaged, corroded, or loose connectors and/or wiring on the fuel pressure sensor circuit
- General problem within the wiring harness between the ECM and the sensor
- Sensor seals out of place or damaged, allowing an incorrect reading
- Intermittent electrical problem in the circuit
- Faulty fuel delivery pressure sensor that needs to be replaced
- Faulty ECM that needs to be replaced
How to troubleshoot CAT Engine 943: first checks
- Visually inspect the fuel pressure sensor connector and wiring harness for damage, corrosion, or pinch points
- Check that the sensor's seals are properly seated and not displaced
- Wiggle-test the harness and connector while watching for the code to reset, to help identify an intermittent connection
- Verify the sensor signal wiring is not shorted to +battery voltage, since this is a common cause of an above-normal voltage reading
- If wiring and connectors check out, test or swap the fuel pressure sensor itself
- If the sensor tests good, suspect the ECM as the source of the fault
How the code clears
No separate clearing step is listed beyond repairing the wiring, connector, sensor, or ECM as needed. Once the underlying fault is corrected, the ECM should stop logging the code on subsequent key cycles. No reset procedure is listed for this code.
Affected models and serial ranges
943 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 943 mean?
It means the ECM detected a signal voltage from the fuel delivery pressure sensor that is above the normal expected range. The ECM treats the fuel pressure reading as invalid and uses a default value instead.
Is CAT fault code 943 serious?
CAT states there are no performance effects from this code, so the engine keeps running normally using a default fuel pressure value. It is still worth diagnosing promptly since the ECM is not using real fuel pressure data while the fault is active.
Will code 943 turn on a warning light?
On engines equipped with a warning light for this circuit, the light will illuminate when the code is active. Not all configurations have this light.
What usually causes code 943?
The most common causes are damaged or corroded wiring and connectors, a wiring harness problem, sensor seals out of place, an intermittent electrical fault, a faulty fuel pressure sensor, or a faulty ECM.
Which CAT engines can set code 943?
This code applies to the C10, C11, C12, C13, C15, C16, C27, and C32 engine families.
How do I fix CAT code 943?
Start by inspecting the connectors and wiring for damage or corrosion, check the sensor seals, and look for an intermittent connection. If the wiring checks out, test or replace the fuel pressure sensor, and if that does not resolve it, the ECM may need to be replaced.
Does code 943 affect engine power?
According to CAT's diagnostic description for this fault, there are no performance effects, since the ECM substitutes a default fuel pressure value and continues normal operation.