CAT Engine 16275 Fault Code: Fuel Pump Relay:Current Below Normal
Also called Fuel Pump Relay : Current Below Normal, Fuel Pump Relay Current Below Normal, Fuel Pump Relay Open Circuit, Fuel Pump Relay current below normal, Fuel Pump Relay open circuit
Fuel Pump Relay:Current Below Normal · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 16275 (SPN 1627 / FMI 5) sets when the ECM detects an open circuit or a short to battery voltage at the fuel pump relay output for 60 seconds, with the driver output off. It affects C175, C27, and C32 engines and means the electric fuel priming pump (EFLP) may not run, which can stop the engine from starting or running once fuel supply is lost.
High severity. The fuel pump relay circuit supplies the low pressure fuel system. Once the fault sets, the engine may not start, or if already running, injectors keep firing until the engine stalls from fuel starvation. Not an immediate safety hazard, but it can strand the machine and should be diagnosed before the next start attempt.
What does CAT Engine error code 16275 mean?
Code 16275 points to a problem with the fuel pump relay circuit that controls the electric fuel priming pump (EFLP). This pump supplies positive fuel pressure to the low pressure side of the fuel system, including the high-pressure fuel pump on some models. When the keyswitch is turned to ON, the ECM energizes the relay so battery power reaches the priming pump through the relay's normally open contacts.
The ECM sets this code when it detects either an open circuit or a short to battery voltage at the relay output, while the ECM itself is not commanding the driver on. Because the ECM can only see this fault when the output driver is not activated, the check happens in the periods between active energizing of the relay.
Once the code is active, the fuel pump relay will not operate correctly: the EFLP may fail to run at all, or in some conditions may run continuously, and the engine may not start. If the engine is already running when the fault develops, the injectors continue firing until the engine runs out of usable fuel pressure and stalls.
What triggers a CAT Engine 16275 code?
The ECM logs 16275 when all of these conditions are met: the fuel pump relay driver output is off, an open circuit or a short to +battery voltage is detected at the relay output, and battery voltage is greater than 9 VDC. On some ECM logic, the open circuit or short to battery must persist for 60 seconds before the code sets. The ECM also needs to have been powered for at least 2 seconds, and a low current condition in the EFLP relay circuit must be present for more than 2 seconds before the fault is confirmed. No active 168 diagnostic codes can be present at the same time.
Common causes of 16275
- A problem in the wiring or circuit for the fuel priming pump, including an open or short condition
- A faulty or worn fuel pump relay that needs replacement
- A short between the connector for the fuel pump relay and the ECM
- Damaged or corroded connectors, or general wiring harness damage between the ECM and the relay connector
- Blown fuses or a tripped 20 Amp circuit breaker for the engine ECM
- An intermittent connection issue that only shows up under vibration or temperature change
- A faulty electric fuel priming pump (EFLP) itself needing replacement
- Incorrect supply voltage reaching the relay or pump circuit
- A faulty ECM, though this should only be suspected after wiring, relay, and pump are confirmed good
How to troubleshoot CAT Engine 16275: first checks
- With the key off, inspect all connectors at the fuel pump relay, the ECM, and the EFLP pump for corrosion, looseness, or damage
- Check wire 229-BK for continuity to engine ground
- Inspect and, if needed, repair wire A893-OR between the fuel pump relay connector and the electric fuel priming pump
- Verify that battery voltage is present on terminal 1 at the fuel pump relay connector, and confirm the 20 Amp circuit breaker for the engine ECM has not tripped
- If voltage is present on terminal 1 but the pump still will not run, swap or replace the fuel pump relay and retest
- Use a diagnostic scan tool's Override Parameters test (Diagnostics > Diagnostic Tests > Override Parameters) to energize the fuel pump relay directly while the engine is at 0 rpm, and confirm the EFLP responds during the 120 second test window
- Check for blown fuses in the circuit supplying the relay and pump
How the code clears
No separate clearing step is listed beyond correcting the root cause. The ECM logs the code when the fault conditions are detected; once the open circuit, short to battery, faulty relay, or wiring issue is repaired and the circuit reads normal current and voltage, the code should stop being active on the next key cycle. Running the scan tool's Override Parameters test after the repair helps confirm the relay and pump respond correctly before returning the machine to service.
Affected models and serial ranges
16275 appears in our records across 3 CAT Engine models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| C175 | 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 16275 mean?
It means the ECM detected an open circuit or a short to battery voltage at the fuel pump relay output, with the relay driver off, while battery voltage was above 9 VDC. This affects the electric fuel priming pump's ability to supply fuel pressure to the engine.
Will the engine still run with code 16275 active?
It depends on when the fault develops. If it happens before start, the engine may not start because the priming pump isn't supplying fuel pressure. If it happens while running, the injectors keep firing until the engine runs out of usable fuel and stalls.
Which engines can get this code?
This code applies to CAT C175, C27, and C32 engines that use an electric fuel priming pump and a dedicated fuel pump relay circuit.
What should I check first for code 16275?
Start with the fuel pump relay connector and wiring for corrosion or damage, check wire 229-BK for continuity to ground, verify battery voltage on terminal 1 at the relay connector, and confirm the 20 Amp ECM circuit breaker has not tripped.
Can I test the fuel pump relay with a scan tool?
Yes. Under Diagnostics > Diagnostic Tests > Override Parameters, a technician can energize the fuel pump relay directly for 120 seconds while the engine is at 0 rpm, which helps confirm whether the relay and pump respond correctly.
Does a blown fuse cause this code?
Yes, blown fuses in the fuel pump relay circuit are listed as a possible cause, along with damaged wiring, a faulty relay, or a faulty EFLP pump.
Is code 16275 the same as an ECM failure?
Not usually. ECM replacement is listed as a possible cause, but it should only be considered after the wiring, connectors, relay, and fuel pump have all been checked and ruled out.