Torque Converter/Brake Switch B Circuit
The P0703 code means the vehicle's onboard diagnostic system has detected: Torque Converter/Brake Switch B Circuit. This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- easy
- Estimated cost
- $20 - $150 (parts and labor)
Read and clear transmission codes. Many trans codes are caused by low or burnt fluid -- check level and color before assuming the worst.
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Basic scanners only read engine codes. This reads transmission, ABS, and airbag too.
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Common Symptoms
- Check Engine Light illuminated
- Cruise control does not work
- Brake lights may not function
- Torque converter clutch does not engage
Probable Causes (Ranked by Likelihood)
- Faulty brake light switch Very High
- Misadjusted brake light switch High
- Open or shorted brake switch wiring Moderate
- TCM brake switch input circuit fault Low
Step-by-Step Diagnostic Procedure
-
Check if brake lights function when the pedal is pressed -- no lights suggests a switch problem
-
Inspect the brake light switch at the brake pedal for proper adjustment and operation
-
Check brake switch connector for corrosion or loose fit
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Verify brake switch signal reaches the TCM using a scan tool
-
Replace or adjust the brake light switch as needed
Frequently Asked Questions
Can I drive with code P0703?
Drive short distances with caution. If brake lights are not working, other drivers cannot see when you are stopping. This is a safety concern.
Can a bad brake light switch affect the transmission?
Yes. The TCM uses the brake switch signal to release the torque converter clutch when braking. Without this signal, the engine may stall when stopping.
Is the brake light switch easy to replace?
Yes. It is located at the top of the brake pedal and typically costs $10-$40. It can be replaced in under 30 minutes with basic tools.
Sources
This page is built from documented references. Verify against your own service info before repair work.
P0703 on Diesel, EV & Equipment
The same code ID appears across other engines and platforms. The diagnostic flow varies by manufacturer — these are the platform-specific breakdowns:
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