CAT Engine 47 Fault Code: Cylinder #4 Injector : Not Responding Properly
Also called Clinder #4 Injector - Not Responding Properly, Cylinder #4 Injector Not Responding Properly, Cylinder #4 Injector not Responding Properly, Cylinder #4 Injector not responding properly
Cylinder #4 Injector : Not Responding Properly · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT fault code 47 (SPN 654, FMI 7) means the ECM has determined that the cylinder #4 electronic unit injector is no longer capable of delivering the correct amount of fuel. This is confirmed on the C175 engine family. The warning light comes on, the code is logged, and the engine will be derated until the problem is resolved.
High severity. The engine derates as soon as this code sets, which limits power and can affect machine performance right away. It is not an immediate shutdown-now situation, but it should be diagnosed promptly since fuel delivery to a cylinder is compromised and running derated for long periods is hard on the rest of the engine.
What does CAT Engine error code 47 mean?
Fault code 47 points to the injector on cylinder #4 in a common rail fuel system. Each injector has its own solenoid, which the ECM fires with precisely timed pulses to control how much fuel goes into that cylinder. On the affected engines, the ECM sends 105 V pulses to each injector solenoid at the proper time and duration for the current engine load and speed.
When the ECM decides the cylinder #4 injector can no longer deliver the correct fuel amount, whether from an electrical fault in the circuit or a mechanical problem in the injector itself, it logs code 47, lights the warning lamp, and derates the engine to protect it and limit the effects of uneven combustion.
Because injectors on these engines often share a power supply circuit with another injector while each has its own separate return (ground) circuit back to the ECM, a fault on one injector's return line can sometimes make a paired injector look suspect too. Sorting out which injector or which wire is actually at fault takes a specific test rather than guesswork.
Common causes of 47
- Bad or faulty electronic unit injector (mechanically worn or internally failed)
- Damaged connectors or wiring, including damage that only shows up under vibration
- External engine harness problems
- Short circuit to ground detected on the injector's supply or return line
- Open circuit detected on the supply or return line
- Resistance in the return wires
- Problem with the ECM itself
- Fuel leakage at or around the injector
How to troubleshoot CAT Engine 47: first checks
- Connect the electronic service tool and confirm the active code, then run the Injector Solenoid Test. This test is done with the engine not running and briefly activates each solenoid, listening for an audible click and reporting each circuit as OK, Open, or Short.
- Inspect the wiring harness and connectors at cylinder #4 and its paired injector for corrosion, chafing, loose pins, or damage that might only appear when the harness is flexed or vibrated.
- Check for fuel leakage around the cylinder #4 injector, since leakage is listed as a possible cause.
- Because injectors share a power supply circuit in pairs (except on certain cylinders on some engine variants), check the paired injector's return circuit too, since a short on that return line can make the ECM flag the wrong injector.
- Run the Fuel System Verification Test using the electronic service tool. If the code is still active after this test, the suspect injector should be replaced.
How the code clears
No separate clearing step is listed beyond fixing the root cause. Once the wiring, connectors, or injector problem is corrected, run the Fuel System Verification Test again using the electronic service tool. If the code is still active after that, the recommended procedure is to replace the suspect electronic unit injector and then run the Fuel System Verification Test once more to confirm the fault has cleared. If an injector is replaced, its new injector code (trim file) must be programmed into the ECM; if the ECM itself is replaced, all injector codes must be reprogrammed into the new ECM.
Affected models and serial ranges
47 appears in our records across 1 CAT Engine models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| C175 | Serial range not listed in source records |
Frequently asked questions
What does CAT fault code 47 mean?
It means the ECM has detected that the cylinder #4 electronic unit injector is no longer delivering the correct amount of fuel. It corresponds to SPN 654, FMI 7, and is confirmed on the C175 engine family.
Will code 47 cause the engine to lose power?
Yes. As soon as the code logs, the engine will be derated. The warning light also comes on so the operator knows something needs attention.
Can I keep running the machine with code 47 active?
The engine will run in a derated state, but since a cylinder's fuel delivery is affected, it should be diagnosed and repaired as soon as practical rather than run indefinitely.
How do I tell if it's the injector or just the wiring?
Use the electronic service tool to run the Injector Solenoid Test with the engine off. It activates each solenoid briefly and reports the circuit as OK, Open, or Short, which helps separate a wiring problem from an injector problem. Since injectors share power supply circuits in pairs, also check the paired injector's return circuit.
Do I need to reprogram anything after replacing the injector?
Yes. Each new injector comes with its own injector code that must be programmed into the ECM. If the ECM is replaced, all injector codes across the engine must be reprogrammed into it.
What if the code stays active after I replace the injector?
Run the Fuel System Verification Test again using the electronic service tool. If the code remains active, recheck the wiring, connectors, and the ECM itself, since those are all listed as possible causes.
Is this the same as a general injector fault on other CAT engines?
This page covers code 47 specifically for cylinder #4 as documented on the C175 engine. Other cylinders have their own corresponding codes, and injector circuit details can vary by engine model.