OBD-II trouble code
C0800: Control Module Power Circuit / Device Power Fault
A control module (often the ABS or another chassis module) saw its supply voltage drop too low or spike too high. The vast majority of C0800 cases are a weak battery, corroded terminals, or a high-resistance ground/cable — not the module itself.
Quick facts
- System
- Chassis
- Category
- ABS / Traction Control
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $20 – $400
- DIY difficulty
- Beginner DIY
What does C0800 mean?
C0800 is a control-module power supply code. A module — very commonly the ABS/chassis controller, but it can be others — monitors its own supply voltage, and when that voltage falls below roughly 9 volts or spikes above about 16 volts, the module records C0800 to flag that it isn't receiving stable power. It is rarely a failure of the module itself; instead it is the module reporting that its power or ground is unreliable. Because so many chassis and safety functions depend on steady voltage, the module logs this event and may temporarily disable features like ABS or traction control during the voltage excursion.
The great majority of C0800 codes trace to the basics of the charging and grounding system: a weak or failing battery, corroded or loose battery terminals, a high-resistance negative battery cable or ground strap, or a charging-system fault that lets voltage sag or surge. Damaged power/ground wiring to the specific module and poor connections at its connector are next. Diagnosis is essentially a voltage-drop and battery/charging investigation — confirm a healthy battery and clean, tight grounds before ever suspecting the module. Fixing the power supply almost always clears the code.
Common causes
- Weak, failing, or discharged battery
- Corroded, loose, or dirty battery terminals
- High-resistance negative battery cable or ground strap
- Charging-system fault causing low or high voltage
- Damaged power or ground wiring to the affected module
- Poor or corroded connection at the module connector
- Recent jump-start, battery disconnect, or dead-battery event
Symptoms
- ABS, traction-control, and/or other chassis warning lights on
- Temporary loss of ABS/traction control during the voltage event
- Multiple unrelated modules setting codes together (a voltage clue)
- Hard starting or other low-voltage symptoms
- Intermittent warnings that come and go with electrical load
Diagnostic steps
- 1.Scan all modules; multiple modules with low-voltage codes point strongly at battery/charging/ground.
- 2.Load-test the battery and check its state of charge.
- 3.Verify charging-system output at idle and with loads on (typically ~13.5-14.7V).
- 4.Perform voltage-drop tests on the battery cables and main grounds, including the negative cable.
- 5.Clean and tighten battery terminals and ground connections; inspect the affected module's power/ground wiring.
- 6.Clear the code after correcting the power/ground issue and confirm it does not return under load.
Repair cost
$20 – $400
Many C0800 fixes are inexpensive — cleaning terminals or tightening a ground can cost almost nothing, and a battery is often $120-$300. A cable, ground strap, or charging repair varies. Because it's usually a power/ground problem, avoid replacing the module before the electrical basics are confirmed.
Estimate your repair
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Open the Repair Cost Estimator with battery replacement preselected. Adjust labor rate and vehicle category to fit your situation.
Related repairs
DIY vs shop
This is a beginner-friendly repair. Common hand tools, a free afternoon, and a willingness to follow a procedure are usually enough. The risk of causing a bigger problem is low if you read up on your specific vehicle first.