C1173

Park Brake Switch # 1 Released Circuit Short to Gnd

Chassis Chassis/Safety Brake System Electrical 🔴 Serious — Stop or limit driving 🚫 Do Not Drive
💬

What This Actually Means

In plain language — no jargon

The parking brake switch signal wire is shorted to ground, preventing the ECU from detecting when the brake is released. Think of it like a light switch that's stuck in the "on" position due to a broken wire touching the frame.

⚡

Symptoms You May Notice

3 known symptoms for this code
Parking brake warning light stays illuminated
Transmission may not shift properly or remain in Park
Brake system warning messages on dashboard
🔬

How Your ECU Detects This

Technical sensor logic and voltage thresholds

The ECU monitors the park brake switch circuit voltage. When the brake is released, it expects a high voltage signal; when engaged, it expects low voltage. A short to ground forces the signal to 0V continuously, blocking the ECU's ability to detect brake state changes.

Voltage & Parameter Thresholds

ParameterNormal RangeFault Condition
Park Brake Switch Voltage 5V when released, 0V when engaged Constant 0V or below 0.5V when brake released
Circuit Resistance >10kΩ open, <100Ω closed <500Ω indicating unwanted ground connection
🔧

Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex
1
Wiring harness inspection
Visually trace the park brake switch connector and wiring for damaged insulation, pinches, or corrosion causing a ground short.
2
Park brake switch connector
Disconnect and reconnect the switch connector firmly, cleaning corrosion from terminals with contact cleaner.
3
Park brake switch assembly
Replace the switch if resistance testing confirms internal short or if wiring repair does not resolve the fault.
⚠️

When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code C1173 is classified as a serious fault. If your check engine light is flashing — not just steady — pull over safely and do not continue driving. A flashing CEL indicates an active misfire or critical failure that can cause catalytic converter damage within minutes or permanent engine harm within miles. Contact a certified mechanic immediately. Do not attempt roadside repairs on high-severity codes unless you are trained to do so.

Safety note: OBD-II codes identify the system or circuit where a fault was detected — they do not always identify the exact failed component. A professional mechanic using live sensor data will diagnose the root cause more accurately than replacing parts based on the code alone.
🔄

How to Clear Code C1173

What happens after you fix the fault

Once the fault is repaired, C1173 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.

The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.

✅ Safe to Clear When
  • Fault has been diagnosed and repaired
  • You want to confirm the repair worked
  • Code appeared after a sensor was cleaned
⚠️ Do Not Clear When
  • Preparing for an emissions/PUC test
  • Root cause is still undiagnosed
  • Check engine light is flashing
Emissions test note: Clearing codes resets OBD readiness monitors. Most vehicles need 50–100 km of mixed driving before monitors complete. Do not clear codes immediately before an emissions or PUC inspection.