Brake Switch Input Signal Not Received
The ECU is not receiving a signal from the brake switch.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The brake switch is supposed to send a signal when you press the brake pedal, but the computer isn't getting that signal, which affects things like the cruise control and engine braking.
What the computer is actually seeing
The Engine Control Unit (ECU) expects a voltage signal change from the brake switch when the pedal is pressed. Normally, you should see a transition from 0 volts (brake not pressed) to about 12 volts (brake pressed) within 50 milliseconds. If the signal stays at 0 volts when the brake is pressed, the ECU sets a fault code.
What a healthy reading looks like
0 volts (not pressed), 12 volts (pressed)
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. Check the brake fluid level. If low, top off and see if the code returns. Decision: code returns? Yes: go to step 2; No: issue resolved.
- 22. Inspect the brake switch wiring and connector for damage or corrosion. Decision: wiring damaged? Yes: repair wiring; No: go to step 3.
- 33. Using a multimeter, check the voltage at the brake switch connector with the pedal pressed. Expected: ~12V. Decision: voltage present? Yes: replace the brake switch; No: go to step 4.
- 44. Check for continuity between the brake switch connector and the ECU. Expected: continuity when pedal pressed. Decision: continuity present? Yes: replace ECU; No: repair wiring or connectors.
Common causes
- Faulty brake switch
- Wiring issues or shorts in the brake switch circuit
- Corroded or loose connectors at the brake switch or ECU
- Faulty ECU
Typical repair cost
$$
Related codes
Frequently asked questions
Can I drive the vehicle with this code?
Yes, but it may affect cruise control and engine braking.
Will this code come back after clearing it?
If the issue isn't fixed, yes, it will come back.
Why does it seem to pair with SPN 148?
SPN 148 is related to the speed control deactivation; a fault in the brake switch affects both.
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