Cummins fault code 2634
VGT Actuator Controller: bad device or component
What it means
Cummins' description: VGT Actuator Controller - Bad intelligent device or component.
SPN 641 is Engine Variable Geometry Turbocharger Actuator #1. FMI 12 means a smart device or module reported that it has failed internally.
The turbocharger forces air into the engine. Most modern Cummins engines use a variable geometry turbo (VGT) with an electronic actuator. The ECM watches intake manifold pressure, turbo speed and compressor temperatures to control boost.
What the lamp means
A red stop lamp means Cummins treats this as serious. Stop the engine as soon as you can do it safely and get it checked before running it again.
Green, yellow, red: three ways this can look
The same code can be a quick fix or a reason to shut down. Match your situation to the closest example. Cummins rates this a red stop lamp code, so if the red lamp is on, go by the red example.
Keep an eye on it
A brief underboost code climbing a hill that clears, with normal power the rest of the time.
Schedule a repair
Noticeable power loss, black smoke, or amber lamp with a boost or VGT code. Get it checked. Boost leaks and sticky VGT actuators get worse and hurt fuel economy.
Stop and get help
Loud whine or grinding from the turbo, heavy smoke, oil pouring out of the exhaust, or a stop lamp. Shut it down. A failing turbo can feed parts or oil into the engine.
Common causes
FMI 12 is an electrical or signal fault, so start with the circuit:
- VGT actuator internal fault or wiring problem (common)
- Boost or intake manifold pressure sensor failed or plugged
- Turbo speed sensor or wiring fault
- Actuator power, ground or network connection problem
If the circuit checks out, the reading may be real. Other possibilities: boost leak: split charge air hose, loose clamp, cracked charge air cooler; vGT vanes sticking from soot; worn or damaged turbo.
What you can check before calling
- Listen for a new hiss or whistle under load, a typical sign of a boost leak
- Check charge air hoses and clamps for oil or soot
- Check the air filter restriction indicator
- Notice whether power loss happens only under heavy load or on hills
Clearing the code without fixing the cause usually brings it right back, and on emissions systems it can restart derate timers.
Engines and sources
Listed by Cummins for: QSB 6.7, QSL 9, QSX 15, QSB 4.5. Cummins uses the same fault code numbers across its electronic engines, including on-highway models like the ISB/B6.7, ISL/L9 and ISX/X15, though not every code applies to every engine or software level. Source: Cummins Tier 4 Fault Codes. Always confirm with Cummins service information (QuickServe) for your engine serial number.
Same SPN, other failure types
- 1894 SPN 641 FMI 9
VGT Actuator Driver Circuit: abnormal update rate - 1898 SPN 641 FMI 13
VGT Actuator Controller: out of calibration - 1962 SPN 641 FMI 15
VGT Actuator Driver Over Temperature (Calculated): reading above normal (least severe) - 1976 SPN 641 FMI 15
VGT Actuator Driver Over Temperature (Calculated): reading above normal (least severe) - 2198 SPN 641 FMI 11
VGT Actuator Driver Circuit: root cause not known - 2387 SPN 641 FMI 7
VGT Actuator Driver Circuit (Motor): not responding / out of adjustment - 2449 SPN 641 FMI 13
VGT Actuator Controller: out of calibration - 2635 SPN 641 FMI 31
VGT Actuator Driver Circuit: condition exists
Related Turbo, VGT and boost codes
- 2451 SPN 2789 FMI 16
Turbocharger Turbine Intake Temperature: reading above normal (moderately severe) - 2347 SPN 2629 FMI 15
Turbocharger Compressor Outlet Temperature (Calculated): reading above normal (least severe) - 2346 SPN 2789 FMI 15
Turbocharger Turbine Intake Temperature: reading above normal (least severe) - 2973 SPN 102 FMI 2
Intake Manifold 1 Pressure: erratic or intermittent signal - 2288 SPN 103 FMI 15
Turbocharger 1 Speed: reading above normal (least severe) - 3348 SPN 1176 FMI 1
Turbocharger 1 Compressor Intake Pressure: reading below normal (most severe)
Look up another code
Cummins fault code (like 1922), J1939 SPN and FMI (like SPN 3251 FMI 0), or an OBD-II code (like P0420).
Questions
What does Cummins fault code 2634 mean?
Cummins fault code 2634 is J1939 SPN 641 FMI 12: VGT Actuator Controller - Bad intelligent device or component. In plain terms: vgt actuator controller: bad device or component.
Can I keep driving with Cummins code 2634?
No. Cummins assigns this code a red stop lamp. Stop the engine as soon as it's safe and have it checked before running it again. Look at the green, yellow and red examples on this page to judge your situation.
What is the SPN and FMI for Cummins code 2634?
SPN 641 identifies the part or system (Engine Variable Geometry Turbocharger Actuator #1). FMI 12 describes the type of failure: bad device or component.
What usually causes Cummins code 2634?
The most common causes are: vGT actuator internal fault or wiring problem (common); boost or intake manifold pressure sensor failed or plugged; turbo speed sensor or wiring fault.
Diesel down in the Midlands?
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