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 its function. To identify which circuit code applies to a system, refer to the Circuit Identification Code Chart. This chart shows the main circuits only and does not show the secondary codes that may apply to some models.
| 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 | TEMPORARY |
| Z | GROUNDS |
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.