CAT Engine 2633 Fault Code: Digital Sensor Supply short to +batt
Also called Digital Sensor Power Supply (8V Or 12V) : Voltage Above Normal, Digital Sensor Power Supply (8V Or 12V) Voltage Above Normal, Digital Sensor Power Supply (8V Or 12V) voltage above normal, Digital Sensor Power Supply (8V Or 12V): Voltage Above Normal, Digital Sensor Supply Short to +Batt, Digital Sensor Supply Short to Batt+
Digital Sensor Supply short to +batt · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 2633 (SPN 678 / FMI 3) means the ECM has detected the digital sensor power supply voltage reading above normal, often due to a short to Battery+. The ECM defaults all digital sensor values and logs the code, which can cause low engine power until fixed.
Medium severity. Not an immediate shutdown condition, but the ECM ignores real digital sensor data and substitutes default values while the fault is active. This can cause low power or inaccurate readings, so it should be diagnosed the same shift it appears rather than ignored.
What does CAT Engine error code 2633 mean?
Code 2633 relates to the Digital Sensor Power Supply circuit inside the CAT ECM. This circuit feeds power to digital-type sensors used across various CAT engine families, which can include the throttle position sensor, coolant level sensor, auxiliary temperature sensor, exhaust temperature sensors, and decelerator position sensor depending on the engine model.
The ECM normally supplies a regulated voltage to these sensors, either 12.7 volts (plus or minus 1.0 volt) or 8.0 volts (plus or minus 0.4 volt, or on some systems plus or minus 0.5 volt) depending on which digital sensor supply circuit is involved. When the ECM reads voltage on this supply line above the normal range, indicating a possible short to Battery+, it sets code 2633.
Once active, the ECM flags all digital sensor data on that circuit as invalid and substitutes default values in memory, regardless of what the sensors are actually reading. Because digital sensors are not protected from overvoltage the way the ECM internal circuit is, a hard short to Battery+ can potentially damage the sensor itself, not just trigger the code.
What triggers a CAT Engine 2633 code?
The ECM sets this code when it reads Digital Sensor Supply voltage above 13.7 volts DC for two seconds on the 12-volt supply circuit (normal is 12.7 volts plus or minus 1.0 volt), or above 8.5 volts DC for two seconds on the 8-volt supply circuit (normal is 8.0 volts plus or minus 0.4 volt) after the ECM has been powered for three seconds.
Common causes of 2633
- Damaged or corroded connectors and wiring in the digital sensor supply circuit
- A short circuit between the digital sensor supply line and Battery+
- Problem within the wiring harness itself
- A faulty or damaged digital sensor (throttle position, coolant level, auxiliary temperature, exhaust temperature, or decelerator position sensor depending on engine model)
- A defective or faulty ECM
- Intermittent connection issues in the circuit
How to troubleshoot CAT Engine 2633: first checks
- Check the diagnostic lamp or scan tool for the active code and confirm which digital sensors are affected on your engine model
- Inspect all connectors, pins, and sockets tied to the digital sensor supply circuit, and make sure they are fully inserted and coupled
- Look over the harness and wiring for corrosion, abrasion, or pinch points that could cause a short to Battery+
- Verify all connections and grounds are tight and free of corrosion
- Check for any other active sensor-specific diagnostic codes, since a sensor may have been damaged by overvoltage and need replacement
- If auxiliary temperature is used, confirm it has been programmed to Enabled on the configuration screen of the electronic service tool, otherwise it will show Unavailable and complicate diagnosis
How the code clears
No separate clearing step is listed. Repair the wiring, connector, sensor, or ECM issue causing the overvoltage condition, then verify the digital sensor supply voltage reads within the normal range. Once the underlying short or fault is corrected, the ECM should stop logging the code on the next active check. No reset procedure beyond fixing the fault is described.
Affected models and serial ranges
2633 appears in our records across 5 CAT Engine models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| C10 | Serial range not listed in source records |
| C12 | Serial range not listed in source records |
| C15 | Serial range not listed in source records |
| C16 | Serial range not listed in source records |
| C27 | Serial range not listed in source records |
Frequently asked questions
What does CAT code 2633 mean?
It means the ECM detected the digital sensor power supply voltage reading above normal, generally caused by a short to Battery+ somewhere in that circuit. The ECM responds by setting all affected digital sensors to default values.
Will code 2633 cause a loss of power?
It can. Since the ECM ignores actual digital sensor readings and substitutes default values while the fault is active, the engine may experience low power depending on which sensors are affected.
Which sensors are affected by code 2633?
It depends on the engine model. Affected digital sensors can include the throttle position sensor, coolant level sensor, auxiliary temperature sensor, left and right exhaust temperature sensors, and decelerator position sensor.
Can a short to Battery+ damage anything?
The ECM's internal digital sensor supply circuit is short circuit protected against Battery+ or Battery- shorts and will not be damaged. However, the digital sensors themselves are not protected from overvoltage, so a short to Battery+ may damage a connected sensor.
What voltage should the digital sensor supply read normally?
Depending on which supply circuit is involved, normal voltage is either 12.7 volts plus or minus 1.0 volt DC, or 8.0 volts plus or minus 0.4 volt DC (some systems list plus or minus 0.5 volt).
Is there a reset procedure for code 2633?
No reset procedure is listed for this code. Repairing the wiring, connector, or sensor fault causing the overvoltage condition should allow the code to clear on its own once conditions are normal.
Do I need a circuit breaker on this circuit?
No. CAT states the digital sensor supply is output short circuit protected internally, so a circuit breaker is not required for this circuit.