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P0703 is usually a simple brake light switch. Many vehicles have two brake switches - one for brake lights, one for the TCM (switch B). A $15–$30 part swap fixes the majority of P0703 codes. Confirm by checking that brake lights work normally before spending more. Brake switches on Amazon ↑
🗺️ Where Is the Problem?
Blueprint view - P0703 fault localized to the transmission control system / solenoid body
These are statistical causes across ALL vehicles - your exact car may rank differently
For example, on a Honda 4-cyl the downstream O2 sensor causes P0703 64% of the time, but on a GM 5.3L V8 the catalytic converter is the cause 71% of the time. Get a probability ranking built specifically for your year, make, model, and mileage.
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🎯 Top Causes & Probability
70%
#1 - Most Likely
Failed Brake Light Switch (B)
The secondary brake switch above the brake pedal has failed open, shorted, or has internal contact wear. Replacement is a 15-minute job under the dash. On many Chrysler/Dodge vehicles this switch is a known weak point and frequently fails between 80k–120k miles.
🔩 Part
$15–$45
👨🔧 Labor
$0–$80
⚡ DIY Difficulty
Easy
20%
#2 - Check First
Misadjusted Brake Pedal Switch
The brake switch position has shifted or the pedal striker is bent, so the switch never fully closes/opens. Adjustment to the proper plunger depth (usually 1–3 mm preload) restores normal operation without parts.
🔩 Part
$0
👨🔧 Labor
$0–$60
⚡ DIY Difficulty
Easy
10%
#3 - Less Common
Wiring Fault to TCM
Damaged wire, corroded connector, or open ground between the brake switch and the TCM. Most often caused by a previous under-dash repair or aftermarket trailer brake controller install. Repair the wire or connector to fix.
🔩 Part
$10–$50
👨🔧 Labor
$80–$200
⚡ DIY Difficulty
Medium
🚗 Most Affected Vehicles
🔧 Step-by-Step Diagnosis
- Verify brake lights work normally - Step on the pedal with a helper or back to a wall and confirm both brake bulbs light. If brake lights flicker or do not light, the primary switch is also bad and may be the same part on some vehicles.
- Locate brake switch B - On most Chrysler products it's the second switch on the brake pedal bracket. On Fords it's integrated. Consult a service manual for the exact location and electrical connector pinout for your vehicle.
📍 Find a Trusted Shop Near You
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Tips for Choosing a Shop
- Ask if they charge a diagnostic fee and whether it applies toward the repair
- Request a written estimate before approving any work
- Ask specifically about the part brand - OEM vs. aftermarket matters for this code
- Check Google reviews for recent mentions of the specific repair you need