Brake System Control Module External Fault
The brake system control module has detected an external fault.
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What it means (plain English)
The computer in your braking system has noticed something wrong outside of itself, usually related to wiring or connection issues.
What the computer is actually seeing
The brake control module monitors inputs from various sensors. When it detects irregular signals or faults in the wiring or its connections, it throws the C1198 code. It may also see erratic voltage levels or no signal at all from necessary inputs.
What a healthy reading looks like
Normal input signals should show voltages between 0 to 5 volts, with a typical operating point close to 2.5 volts for most sensors. A smooth, steady voltage is expected.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Inspect wiring and connectors for damage or corrosion, particularly around the brake control module; repair any issues found.
- 22. Check the voltage supply to the brake control module with a multimeter; voltages should be between 12-14 volts with the ignition on.
- 33. Test the brake pedal position sensor; it should provide a steady voltage output between 0 to 5 volts as the pedal is depressed.
- 44. If no wiring issues or faulty sensor found, scan for other codes which may indicate a related issue with the ABS module.
Common causes
- Damaged wiring harness to the brake control module
- Corroded or loose connectors
- Faulty brake pedal position sensor
- Failing anti-lock brake system (ABS) module
- Intermittent or low voltage supply to the brake control module
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's best to address this code promptly, as it could affect braking performance. If you feel any unusual brake behavior, do not drive until inspected.
Will this code come back after clearing?
If the underlying issue isn't resolved, yes, the code will likely return.
Why does this code sometimes pair with ABS issues?
Both codes relate to the brake system; a fault in the ABS module can trigger this code as well.
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