Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Circuit Functions
All circuits in the diagrams use an alpha/numeric code to identify the wire and it's function. To identify which circuit code applies to a system, refer to the chart below. This chart shows the main circuits only and does not show the secondary codes that may apply to some models.
Circuit Identification Code Chart
| Circuit | Function |
|---|---|
| A | Battery Feed |
| B | Brake Controls |
| C | Climate Controls |
| D | Diagnostic Circuits |
| E | Dimming Illumination Circuits |
| F | Fused Circuits |
| G | Monitoring Circuits (Gauges) |
| H | Multiple |
| I | Not Used |
| J | Open |
| K | Powertrain Control Module |
| L | Exterior Lighting |
| M | Interior Lighting |
| N | Multiple |
| O | Not Used |
| P | Power Option (Battery Feed) |
| Q | Power Options (Ignition Feed) |
| R | Passive Restraint |
| S | Suspension/Steering |
| T | Transmission Transaxle Transfer Case |
| U | Open |
| V | Speed Control, Wiper/Washer |
| W | Wipers |
| X | Audio Systems |
| Y | Open |
| Z | Grounds |
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.