C0900
Device Voltage High
What it means
C0900. Device Voltage High. This Chevy-enhanced code applies to Impala, Colorado, Silverado, Malibu.
Findings, check these first
- Overcharging alternator driving system voltage above specification
- Faulty voltage regulator inside the alternator
- Poor battery cable connections causing charging spikes
- Jump-start voltage spike corrupting the EBCM voltage monitor
Standard procedure
- Measure charging voltage with the engine running; sustained readings above specification indicate an alternator fault
- Inspect battery cables and EBCM ground connections for looseness and corrosion
- Test alternator output under electrical load before replacing it
- Clear the code after charging repairs and confirm it does not reset
- Replace the alternator only on failed output tests, then verify EBCM data stays in range
Look up another code
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Sources and review
Review: no source links are recorded for this entry.
Last updated 2026-09-25.
Report a correction for C0900. Include your vehicle, the issue and a source if you have one.
This fault is part of the GM ABS and StabiliTrak family. The GM ABS and StabiliTrak codes guide covers the check order.