CAT Engine 414 Fault Code: 8 Volt DC Supply short to ground
Also called 8 Volt DC Supply - Voltage Below Normal, 8 Volt DC Supply : Voltage Below Normal, 8 Volt DC Supply Short to Ground, 8 Volt DC Supply Voltage Below Normal, 8 Volt DC Supply voltage below normal, 8 Volt DC Supply: Voltage Below Normal, 8 Volt DC Supply:Voltage Below Normal, ECU 8 Volts DC Supply : Voltage Below Normal, Volt DC Supply : Voltage Below Normal
8 Volt DC Supply short to ground · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT fault code 414 (SPN 678, FMI 4) means the ECM has detected that the 8 volt DC supply feeding the throttle position sensor, or in some cases the related 5 volt sensor supply circuits, has dropped below normal voltage. The ECM defaults affected sensor values and logs the code. This affects the C10, C11, C12, C13, C15, C16, C175, C18, C27, and C32 engine families.
High severity. The engine can often keep running on default sensor values, but throttle position and other pressure readings become unreliable. Left unaddressed, this can cause poor performance, unexpected derates, or sensor damage if the root cause is a short to battery voltage.
What does CAT Engine error code 414 mean?
The ECM generates a regulated 8.0 ± 0.4 VDC supply for the throttle position sensor, along with a separate 5.0 ± 0.2 VDC supply that feeds a list of other sensors such as the engine oil pressure sensor, intake manifold pressure sensor, atmospheric pressure sensor, fuel pressure sensor, crankcase pressure sensor, turbocharger inlet pressure sensor, and on some engines the aftertreatment ID module and NRS pressure sensors.
Code 414 specifically points to the 8 volt supply circuit for the throttle position sensor reading below normal voltage. Supply voltage travels from the ECM to terminal 1 (or terminal A on some harness configurations) of the sensor connector, with the sensor return going back to terminal 2 (or terminal B).
The ECM has internal short circuit protection so a short to battery will not damage the ECM's power supply itself. However, the sensors are not protected from overvoltage, so a short from the supply line to +Battery can damage a connected sensor. When this code is active alongside other sensor supply diagnostic codes, a damaged sensor is a real possibility and should be checked once the wiring problem is fixed.
What triggers a CAT Engine 414 code?
The digital sensor supply voltage is below normal for one second.
Common causes of 414
- Damaged or corroded connectors and/or wiring in the sensor supply circuit
- Electrical problem internal to the throttle position sensor itself
- Sensor needs to be replaced due to internal failure
- Intermittent connection problem in the harness
- Problem within the wiring harness, including a supply wire shorted to another wire or shorted to engine ground
- Problem with the ECM itself
How to troubleshoot CAT Engine 414: first checks
- Inspect the throttle position sensor connector and wiring harness for damage, corrosion, or loose pins at terminal 1/A (supply) and terminal 2/B (return)
- Check for any other active sensor diagnostic codes at the same time. If other codes are active, a sensor may already be damaged from an overvoltage event and should be tested or replaced
- Trace the harness for chafe points or pinch points where the supply wire could be shorted to ground or to another wire
- Wiggle-test the harness and connector with the engine off and key on to look for intermittent voltage drops
- Verify the ECM's 8 volt supply output directly at the ECM connector to rule out an internal ECM fault before condemning the harness or sensor
How the code clears
No separate clearing step is listed for this code beyond repairing the sensor supply circuit. Once the wiring, connector, or sensor issue is fixed, check for and clear any active sensor diagnostic codes, then confirm the code does not return during normal engine operation.
Affected models and serial ranges
414 appears in our records across 10 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 |
| C175 | Serial range not listed in source records |
| C18 | 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 414 mean?
It means the ECM has detected the 8 volt DC supply voltage, which normally feeds the throttle position sensor, is below normal. The ECM sets the affected sensor to a default value and logs the code.
Can I keep driving or operating with code 414 active?
The engine can typically keep running because the ECM substitutes a default value for the affected sensor, but throttle response and related engine control may not behave normally. Because a short to battery voltage can damage the sensor, it should be diagnosed and repaired as soon as practical rather than ignored.
Does code 414 mean the sensor is bad or the wiring is bad?
It can be either. CAT lists damaged connectors or wiring, an internal sensor electrical problem, a bad sensor, an intermittent connection, a harness short, or a faulty ECM as possible causes. Checking the wiring and connectors first is the quickest way to narrow it down.
Is code 414 the same as the 5 volt supply codes?
No. Code 414 (SPN 678, FMI 4) is specific to the 8 volt supply used for the throttle position sensor. Separate diagnostic codes cover the 5 volt supply used by pressure sensors and other components; those are different codes even though the underlying supply circuit concept is similar.
Could this code mean a sensor got damaged?
Yes, it's possible. The sensors are not protected from overvoltage, so if the supply line shorted to +Battery, a connected sensor could be damaged. Repair the supply circuit first, then check for any other active sensor diagnostic codes to confirm sensor condition.
Where do I check the wiring for this code?
Check the sensor connector terminal 1 (or terminal A) for the supply voltage and terminal 2 (or terminal B) for the sensor return, tracing the harness between the ECM and the throttle position sensor connector for damage, corrosion, or shorts.