C1000 – Manufacturer Controlled DTC

By Bojan Popic (Contact Me)
Last Updated 2023-03-30
Master Mechanical Engineer

Table of Contents

1. What Does Code C1000 Mean?
2. Where is the C1000 sensor located?
3. What are the common causes of code C1000?
4. Get Help with C1000

What Does Code C1000 Mean?

OBD II fault code C1000 is a manufacturer-specific trouble code whose definition differs depending on the car maker. However, several brands are far more affected by this issue, and that’s what this article will focus on.

First is Chrysler – which also owns Ram and Dodge – who defines the C1000 trouble code as an invalid signal between the master cylinder pressure applied and the Brake lamp switch output. This is detected by the ABS, with the issue being present for at least two minutes. Furthermore, Mercedes-Benz has an almost identical description for this trouble code, whose vehicles commonly suffer from it. Lastly, certain cars made by Mitsubishi are known to have issues with recurring C1000 trouble codes, which is here defined as an Abnormality in a stoplight switch circuit.

The C1000 trouble code in mentioned vehicles will be set when the ABS control module detects a signal from the brake light switch without corresponding brake activation. Or, to put it simply, this happens when the car determines the brake switch is sending a false ON signal because it’s not braking. Apart from brake lights being constantly on, this also disables the ABS and cruise control if the vehicle has it.

Still, remember some car makers might have a different explanation for the C1000 trouble code.

Where is the C1000 sensor located?

Almost all cars on the road have a brake lamp switch, which gets activated when the driver presses the brake pedal. When this is done, it sends a signal to the vehicle’s PCM and other control modules, which use it for several things.

First is the brake light, which is triggered every time the switch is activated. Then, there are the ABS and other driver-aid systems, which need to know if the brake is being applied. Additionally, the cruise control in vehicles that have it gets deactivated when the brakes are applied. And lastly, in many cars, the driver must press the brake before turning on the engine. Again, this will only happen with a valid signal from the brake lamp switch.

Due to the nature of its job, this component is always located near the brake pedal. Most cars will have it under the dashboard, next to where the pedal meets the firewall.

What are the common causes of code C1000?

The C1000 trouble code is set when the brake lamp switch continuously sends an ON signal, which narrows down potential causes.

Faulty brake light switch
The switch itself is a simple device and can fail in two ways, with developing an internal short being one of them. In addition, the rubber stop between the switch’s tip and brake pedal may fall off or wear out. As a result, the brake pedal, once released, will not deactivate the switch, as there will be no contact between them.

Damaged wiring
Like other sensors, the brake lamp switch has wiring connecting it to the car’s electrical system. And its insulation may get mechanically damaged, creating a short and consistent false ON signal.

Jeep recall over failing brake lamp switches
Some 2017 – 2018 Jeep Wranglers and Dodge Caravans were equipped with brake lamp switches that proved very prone to failure. In many cases, these would fail within several months of use. This prompted Chrysler, who owns both brands, to recall the affected vehicles in 2018 and replace the faulty brake lamp switches with upgraded ones.

Incorrectly adjusted Mitsubishi brake switches
In many Mitsubishi cars, the brake lamp switch’s travel can be adjusted, which sometimes may be done incorrectly. How to check and correct this is described and illustrated on page 3 of this Mitsubishi Tech Talk document.

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