VGT Actuator - Voltage Below Normal
The CUMMINS-2797 (Cummins) diesel fault code means: VGT Actuator - Voltage Below Normal. This is a moderate severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- advanced
- Estimated cost
- $400-$1,500
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Common Symptoms
- Power loss especially under load
- Turbo lag or sluggish acceleration
- Black smoke under acceleration
- Higher than normal EGT
- Check Engine Light on
Probable Causes (Ranked by Likelihood)
- EGR valve carbon-seized in partially open position Very Likely
- Failed EGR position sensor Likely
- Clogged EGR cooler restricting flow Likely
- VGT actuator stuck from carbon or corrosion Possible
- Leaking EGR cooler causing coolant loss Possible
Frequently Asked Questions
What is Cummins fault code 2797?
Cummins fault code 2797 indicates: VGT Actuator - Voltage Below Normal. It is a moderate-severity fault in the aftertreatment or emissions system.
Can I drive with Cummins fault code 2797?
Yes, short-term driving is typically safe with fault 2797, but the fault will illuminate the Check Engine Light and must be diagnosed soon. Monitor for power loss, unusual noises, or gauge changes and pull over if conditions worsen.
How much does it cost to fix Cummins fault 2797?
Repair cost is approximately $400-$1,500 including parts, labor, and any dealer programming required. DIY repairs (sensor replacement) fall at the low end; pump, aftertreatment, or ECM work falls at the high end and usually requires INSITE diagnostic software.
What actually makes the computer set this boost code?
California's heavy-duty OBD regulation sets the underboost trip point where a decrease from commanded or expected boost would push NMHC, CO or NOx past 2.0 times the applicable standards, or PM past the standard plus 0.02 g/bhp-hr (Title 13 CCR 1971.1, section (e)(4.2.1)). As with EGR, it must also flag the system reaching its control limits without achieving commanded boost — worth knowing before condemning a turbo that is physically moving. This threshold comes from the heavy-duty OBD regulation, which covers 2010 and later heavy-duty engines. If your engine is in a pickup at or under 14,000 lb GVWR it is certified under the separate medium-duty rule instead, so treat this as the design intent rather than your engine's exact limit.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
Connect INSITE and command the EGR valve through its full range while monitoring position feedback for smooth response.
Remove EGR valve and inspect for carbon buildup; soak in carbon cleaner and reinstall or replace if deeply fouled.
Measure VGT actuator voltage and calibration via INSITE output test -- command 0%/50%/100% and verify position.
Inspect EGR cooler for internal leakage (coolant loss or steam from exhaust) -- pressure test if suspect.
Check turbocharger for shaft play, oil leaks at seals, and smooth spool under throttle.
Verify EGR differential pressure and temperature sensors read rational values on INSITE data list.
Sources 2
This page is built from documented references. Verify against your own service info before repair work.
- California Code of Regulations, Title 13 section 1971.1 (Heavy-Duty OBD)malfunction criteria, section (e)
- SAE J1939-73Application Layer: Diagnostics (defines the SPN/FMI fault-identifier framework)
Commonly Affected Vehicles
- Peterbilt 579, 567 with Cummins ISX/X15
- Kenworth T680, T880 with Cummins X15
- Freightliner Cascadia with Cummins ISX15
- Ram 2500/3500 with 6.7L Cummins
- Freightliner M2 106 with Cummins ISL9/L9
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