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 2026-07-21
TL;DR
Fault code 943 (SPN 94 / FMI 3) means the ECM sees fuel delivery pressure signal voltage above normal. The ECM logs the code, flags fuel pressure as invalid data, and substitutes a default value. There are no performance effects reported for this specific fault, but the underlying wiring issue should still be fixed.
Medium severity. CAT states there are no performance effects from this code alone since the ECM substitutes a default fuel pressure value. However, the electrical fault behind a high-voltage signal (a short to +battery or a wiring problem) can affect other circuits sharing the same harness run, so it should be diagnosed within the shift rather than ignored.
What does CAT Engine error code 943 mean?
Code 943 fires when the ECM's fuel delivery pressure sensor circuit reads a voltage above the normal expected range. This is an analog/active sensor signal, and CAT's alternate descriptions for this same code describe it as the fuel pressure signal being open or shorted to +battery voltage.
When this happens, the ECM cannot trust the fuel pressure reading. It logs the code, flags the fuel pressure value as invalid, and substitutes a default value in its place so the engine keeps running. CAT explicitly states there are no performance effects tied to this substitution.
This is different from a low-voltage or open-circuit fault on the same sensor (covered by other codes in this family). A high-voltage reading almost always points to the signal wire picking up power it shouldn't, either from a short to the battery supply or a wiring/connector fault feeding excess voltage into the ECM's sensor input.
Common causes of 943
- Damaged or corroded connectors, or wiring problems in the harness feeding the fuel pressure sensor
- A general problem within the harness itself, including chafed wire insulation that lets the signal wire contact a powered circuit
- Sensor seals out of place, allowing moisture or contamination to affect the sensor's internal circuit
- An intermittent electrical problem in the connectors, harness, or sensor connection
- A faulty fuel delivery pressure sensor that needs to be replaced
- A faulty ECM that is misreading the signal or supplying incorrect voltage internally
How to troubleshoot CAT Engine 943: first checks
- Inspect the fuel pressure sensor connector and mating harness connector for corrosion, moisture, bent pins, or backed-out terminals
- Visually trace the harness from the sensor toward the ECM looking for chafe points, pinches, or rub-through where the signal wire could be contacting a powered wire or +battery source
- Check the sensor's mounting and seals for damage or displacement that could point to a compromised sensor
- Wiggle-test the harness and connectors with the engine off and key on to look for an intermittent voltage spike on the signal line, since several CAT causes list this as an intermittent problem
- If wiring and connectors check out, test the sensor itself against CAT's sensor signal test procedure, then substitute a known-good sensor if available
- If the sensor tests good and wiring is clean, suspect the ECM as CAT lists ECM replacement as a possible cause
How the code clears
No separate clearing step or reset procedure is listed for this code beyond repairing the wiring, connector, seal, or sensor problem causing the high-voltage signal. Once the fault condition is corrected, the code should stop being active; clear the logged code with a diagnostic tool and confirm it does not return during a test cycle.
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 fault code 943 mean?
It means the ECM detected the fuel delivery pressure sensor's signal voltage above the normal expected range. The ECM responds by flagging the fuel pressure reading as invalid and using a default value instead.
Will code 943 cause a loss of engine power?
CAT states there are no performance effects from this code. The ECM simply substitutes a default fuel pressure value, so the engine keeps running, but the underlying wiring or sensor fault should still be repaired.
What usually causes a fuel pressure sensor to read voltage above normal?
The most common causes are damaged or corroded connectors, harness wiring problems including chafed insulation shorting the signal wire to a powered circuit, displaced sensor seals, a faulty sensor, or in some cases a faulty ECM.
How is code 943 different from code 944?
Code 943 is a voltage-above-normal fault, meaning the fuel pressure signal is reading too high or shorted toward +battery voltage. Code 944 is the opposite fault, a fuel pressure signal short to ground, which reads voltage too low. If your symptom looks like a low or grounded signal instead of a high one, check the 944 page instead.
Is this the same as the throttle position sensor codes 913 or 914?
No. Codes 913 and 914 apply to the throttle position sensor circuit, not the fuel delivery pressure sensor. Code 943 is specific to the fuel pressure signal reading above normal voltage.
Can an intermittent connection cause code 943 to come and go?
Yes. CAT lists an intermittent problem in the connectors or harness as a possible cause, so the code can appear and clear on its own if a marginal connection is involved. A wiggle test while monitoring the signal can help find this type of fault.
Do I need to replace the sensor or the ECM to fix code 943?
Not necessarily. Start with the wiring, connectors, and seals since those are the most common causes. Only move to sensor or ECM replacement after confirming the harness and connectors are clean and intact.