CAT Engine 21314 Fault Code: 5 Volt Sensor DC Power Supply #2 : Voltage Below Normal
Also called 5 Volt Sensor DC Power Supply #2 - Voltage Below Normal, 5 Volt Sensor DC Power Supply #2:Voltage Below Normal, Sensor Supply Voltage 2 : Voltage Below Normal
5 Volt Sensor DC Power Supply #2 : Voltage Below Normal · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 21314 (SPN 3510, FMI 4) means the ECM's second regulated 5-volt sensor supply circuit is reading below normal. This supply feeds a group of pressure sensors and buffers used across the C13, C15, C175, C18, C27, and C32 engines. The fault points to wiring, connector, sensor, or ECM problems on that shared supply line, and it can leave several sensors defaulted at once, so it's worth treating as a priority diagnosis even though the engine may keep running.
High severity. The engine can keep running with default sensor values substituted, but a weak or missing 5-volt supply can affect multiple pressure sensors at the same time, which reduces the ECM's ability to manage combustion, boost, and aftertreatment correctly. A short from the supply line to battery voltage can also physically damage the sensors on that circuit, so this should be diagnosed promptly rather than run indefinitely.
What does CAT Engine error code 21314 mean?
Fault code 21314 (SPN 3510, FMI 4) applies to CAT C13, C15, C175, C18, C27, and C32 engines. It flags a problem with the ECM's regulated 5-volt DC sensor power supply, specifically the second supply circuit (Sensor Supply Voltage 2), which the ECM has determined is reading below normal voltage.
This 5-volt supply, held at 5.0 ± 0.2 VDC, feeds a shared group of sensors depending on the engine and aftertreatment configuration. Depending on the model, this can include the aftertreatment ID module, atmospheric or barometric pressure sensor, crankcase pressure sensor, engine oil pressure sensor, fuel pressure sensor (filtered fuel pressure), intake manifold pressure sensor, NRS absolute and differential pressure sensors, turbocharger inlet pressure sensors, and exhaust temperature sensor buffers. A separate 8.0 ± 0.4 VDC supply feeds the throttle position sensor on some models, but that circuit is not the one flagged by this code.
Supply voltage to each sensor runs from the ECM to terminal 1 of the sensor connector, with the sensor return routed to terminal 2. The ECM has short circuit protection built in for this internal power supply, so a short to battery voltage will not damage the ECM itself. However, the sensors on the circuit are not protected from overvoltage: a short from the supply line to +Battery can damage them. If this or related sensor supply codes are active, a sensor may already be damaged, so checking for active sensor diagnostic codes after repairing the supply is an important follow-up step.
What triggers a CAT Engine 21314 code?
This description does not list separate numeric set-conditions distinct from the meaning above. Related fault suffixes on the same supply circuit do have set-conditions worth knowing: a -10 code variant activates if a pressure sensor signal stops fluctuating and stays abnormally steady for more than 30 seconds while the engine is running, and a -21 code variant activates when the ECM determines the 5-volt supply is completely missing at the pressure sensor. For both of those related codes, the ECM substitutes a default value for the affected sensor and triggers a snapshot on the -10 condition.
Common causes of 21314
- Damaged, corroded, or loose connectors and/or wiring on the 5-volt sensor supply circuit
- Electrical problem internal to one of the sensors fed by this supply
- A sensor on the circuit that needs to be replaced (faulty sensor)
- Intermittent problem in the circuit or connections
- Problem in the wiring harness feeding the sensor supply
- Problem with the ECM itself
- Sensor passage blocked or obstructed (listed for some sensor variants on this shared supply)
How to troubleshoot CAT Engine 21314: first checks
- With the key off, inspect connectors at the ECM and at each sensor fed by the 5-volt supply #2 circuit for corrosion, pushed-back pins, moisture, or damage.
- Check the wiring harness for chafing, pinched sections, or exposed conductors, especially any spot where the harness could short to +Battery.
- Verify continuity and resistance on the supply (terminal 1) and return (terminal 2) wiring between the ECM and each affected sensor connector.
- Check for any other active sensor diagnostic codes on the same supply circuit. If other codes are active, a sensor may already be damaged and will need testing or replacement.
- Inspect for signs of a short from the supply line to +Battery, since the sensors are not protected from overvoltage and may have been damaged even if the short is no longer present.
- On engines where a sensor passage can become blocked or obstructed, check that the physical sensor port is clear.
- If wiring and sensors check out, suspect the ECM's internal supply circuit and consult a dealer for further ECM-level testing.
How the code clears
No separate reset procedure is listed for this code. Once the wiring, connector, sensor, or ECM problem causing the low supply voltage is repaired, the fault should clear on its own as the ECM sees the 5-volt supply return to normal. It is worth checking for any other active sensor diagnostic codes on the same supply circuit before returning the machine to service, since a damaged sensor may not show a fault code immediately.
Affected models and serial ranges
21314 appears in our records across 6 CAT Engine models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| C13 | Serial range not listed in source records |
| C15 | 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 code 21314 mean?
It means the ECM's second 5-volt regulated sensor power supply is reading below its normal voltage. That supply feeds a shared group of pressure sensors and buffers, so a fault here can affect readings from more than one sensor at once.
Will code 21314 stop my engine from running?
Not necessarily. The ECM substitutes default values for affected sensors, which lets the engine keep running, but with reduced accuracy in the systems those sensors support. It should be diagnosed promptly rather than left alone.
Can this fault damage my sensors?
Yes, potentially. The ECM's internal power supply is protected against a short to battery voltage, but the sensors on the circuit are not protected from overvoltage. A short from the supply line to +Battery can damage them, so check for other active sensor codes after repairing the supply.
Which sensors are affected by the 5-volt supply #2 circuit?
Depending on the engine model, this supply can feed the aftertreatment ID module, atmospheric or barometric pressure sensor, crankcase pressure sensor, engine oil pressure sensor, filtered fuel pressure sensor, intake manifold pressure sensor, NRS absolute and differential pressure sensors, turbocharger inlet pressure sensors, and exhaust temperature sensor buffers.
Is this the same as the throttle position sensor supply?
No. The throttle position sensor runs on a separate 8.0 ± 0.4 VDC supply circuit, which is not the circuit flagged by code 21314.
What's the difference between this code and the -10 or -21 suffix versions on the same circuit?
The -10 suffix activates if a pressure sensor's signal stops fluctuating normally for more than 30 seconds while the engine runs. The -21 suffix activates when the ECM detects the 5-volt supply is completely missing at the sensor. Code 21314 itself covers the supply voltage reading below normal.
What should I check first before replacing parts?
Start with connectors and wiring for corrosion or damage, then check for other active sensor codes on the same circuit, since that helps confirm whether a sensor has already been damaged before you start swapping parts.