CAT Engine 21313 Fault Code: 5 Volt Sensor DC Power Supply #2 : Voltage Above Normal
Also called 5 Volt Sensor DC Power Supply #2 - Voltage Above Normal, 5 Volt Sensor DC Power Supply #2:Voltage Above Normal, Sensor Supply Voltage 2 : Voltage Above Normal, Volt Sensor DC Power Supply #2 : Voltage Above Normal
5 Volt Sensor DC Power Supply #2 : Voltage Above Normal · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT fault code 21313 (SPN 3510, FMI 3) means the ECM has detected the regulated 5-volt sensor supply circuit #2 reading above normal. This supply feeds several pressure sensors and buffers across the C13, C15, C175, C18, C27, and C32 engines. It usually points to a wiring short to a higher voltage source, a damaged connector, or a failed sensor, and it can mean a sensor has already been damaged by overvoltage.
High severity. This code can indicate that a sensor has been exposed to overvoltage and may already be damaged. The ECM defaults the affected sensor value when the fault is active, which can affect engine control and monitoring accuracy, so it should be diagnosed promptly rather than run indefinitely.
What does CAT Engine error code 21313 mean?
Fault code 21313 covers the 5-volt sensor DC power supply circuit #2 on Cat C13, C15, C175, C18, C27, and C32 engines. The ECM sends a regulated 5.0 ± 0.2 VDC to a group of sensors including the aftertreatment ID module, atmospheric pressure sensor, exhaust temperature sensor buffers, crankcase pressure sensor, engine oil pressure sensor, fuel pressure sensor, intake manifold pressure sensor, NRS pressure sensors, and turbocharger inlet pressure sensors. Some engine families narrow this list to fewer sensors such as oil pressure, barometric pressure, crankcase pressure, intake manifold pressure, fuel pressure, and air inlet pressure.
A separate 8.0 ± 0.4 VDC supply feeds the throttle position sensor, though this code specifically concerns the 5-volt supply. Each sensor connector receives supply voltage on terminal 1 and sensor return on terminal 2 from the ECM.
'Voltage Above Normal' (FMI 3) means the ECM is seeing this 5-volt reference circuit reading higher than it should. Because the sensors on this circuit are not protected from overvoltage, a short from the supply line to +Battery can damage the sensors themselves, not just trip the code. The ECM does provide short circuit protection for its own internal power supply, so a short to battery voltage will not damage the ECM, but it may damage the connected sensors.
Common causes of 21313
- Damaged or corroded connectors and/or wiring on the 5-volt supply circuit
- Electrical problem internal to one of the sensors on this supply circuit
- A sensor that has failed and needs replacement
- An intermittent connection or wiring problem
- A problem in the wiring harness feeding the sensor group
- A problem with the ECM itself
- On some sensors, a blocked or obstructed sensor passage
How to troubleshoot CAT Engine 21313: first checks
- Check all connectors on sensors fed by the 5-volt supply #2 circuit for corrosion, moisture, bent pins, or loose terminals
- Inspect the harness wiring between the ECM and the affected sensors for chafing, pinched sections, or exposed conductors that could short to +Battery
- Check for any other active sensor diagnostic codes, since a sensor may have been damaged by overvoltage if this code is active
- Verify terminal 1 (supply) and terminal 2 (return) wiring at each sensor connector match ECM routing and show no cross-contact with battery voltage
- Inspect sensor passages for blockage or obstruction where applicable, since a blocked passage is listed as a possible cause on some models
- If wiring and connectors check good, test the suspect sensor individually and consider ECM-side testing if the problem persists
How the code clears
No separate clearing step is listed. Repair the sensor supply wiring, connector, or sensor as needed, then check for any additional active sensor diagnostic codes to confirm no sensor was damaged by the overvoltage condition before returning the engine to service.
Affected models and serial ranges
21313 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 21313 mean?
It means the ECM detected the regulated 5-volt sensor power supply circuit #2 reading above its normal voltage. This supply feeds several pressure sensors and buffer circuits, and the high reading suggests a wiring short, damaged connector, or failed sensor on that circuit.
Is it safe to keep operating with code 21313 active?
It is not recommended. The sensors on this circuit are not protected from overvoltage, so a short to battery voltage can damage them. The ECM also defaults the value of the affected sensor while the fault is active, which reduces the accuracy of engine monitoring and control.
Which sensors are affected by this fault?
Depending on the engine model, this can include the aftertreatment ID module, atmospheric or barometric pressure sensor, exhaust temperature sensor buffers, crankcase pressure sensor, engine oil pressure sensor, fuel pressure sensor, intake manifold pressure sensor, NRS pressure sensors, and turbocharger inlet pressure sensors.
Can this code damage a sensor permanently?
Yes, it can. A short from the 5-volt supply line to +Battery is not blocked by the sensor's own protection, and Cat notes that a sensor may have been damaged if this code is active. Check for other active sensor codes after repair to confirm.
Will the ECM be damaged by this fault?
The ECM has short circuit protection for its internal power supply, so a short to battery voltage will not damage the ECM itself. The risk is mainly to the connected sensors, not the control module.
What is the difference between the -3, -10, and -21 versions of this code?
The -3 code (Voltage Above Normal, covered on this page) means the 5-volt supply is reading high. Related codes on the same circuit include a -10 code for a signal that stays abnormally steady for more than 30 seconds, and a -21 code for when the 5-volt supply is missing entirely at the pressure sensor.
What should a mechanic check first for code 21313?
Start with a visual and continuity check of connectors and wiring feeding the affected sensors, looking for corrosion, damage, or a short to +Battery. Then check for other active sensor codes, since a damaged sensor is a common result of this fault.