6-Wire Ignition Switch Wiring Diagram

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A 6-wire ignition switch distributes battery power across four key positions — Lock, Accessory, On/Run, and Start — through separate circuits that control accessories, ignition, and the starter motor independently.

The ignition switch is the primary distribution point for vehicle electrical power. Unlike a simple on/off switch, a rotary ignition switch (or its push-button equivalent with a separate rotary cylinder) routes battery power selectively through multiple isolated circuits depending on key position. A 6-wire configuration is common on many light vehicles, trucks, and aftermarket installations where the designer needs separate control over accessories, ignition-powered loads, and the starter circuit.

The six terminals on a typical rotary ignition switch are assigned as follows. Terminal BAT (or B) is the permanent battery positive feed — always live, directly from the battery or from a heavy fuse in the distribution box. Terminal ACC (Accessory) energises only in the Accessory key position (one step before Run), powering entertainment systems, power windows, and ancillary loads without running the ignition system. Terminal IGN1 (or IG1, also called Run) is the primary ignition feed — energised in both Run and Start positions — powering the ECU, fuel pump relay, ignition coils, and instrument cluster. Terminal IGN2 (IG2) is a secondary ignition feed, energised only in Run (not in Start), typically powering loads that must drop out during cranking to prevent voltage sag from affecting sensitive circuits. Terminal ST (or S, Starter) connects to the starter relay or solenoid trigger — energised only in the Start position and spring-loaded to return when released. Terminal ACC2 or LOCK on some designs provides a secondary accessory feed or serves as a steering column lock sense wire.

The key operating logic is important: in Start position, IGN1 and ST are both live. IGN2 drops out during Start so loads like rear window defoggers and HVAC blower do not compete with the starter for current. On release to Run, ST drops, IGN2 re-energises, and the engine runs normally.

Aftermarket installations — alarm systems, remote starters, push-button conversions — must replicate this multi-position switching logic exactly. Collapsing all outputs onto a single switched wire is a common wiring fault that causes loads to energise at the wrong time or fail to drop out during cranking.

How to wire 6 wire ignition switch diagram

Obtain the correct wiring diagram for the specific vehicle Ignition switch terminal designations, wire colours, and connector configurations differ significantly between manufacturers and model years. Do not assume a universal layout. Source the OEM service manual or a vehicle-specific wiring diagram before touching any ignition switch wiring.
Disconnect the battery negative terminal The BAT terminal of the ignition switch is permanently live and may carry 80–100 A capability. Always disconnect the battery negative cable before working anywhere near the steering column wiring. Many vehicles also have an airbag module in this area — allow at least 60 seconds after battery disconnection for airbag capacitors to discharge.
Release the steering column covers and locate the ignition switch connector The rotary switch barrel connects to the electrical switch unit via a mechanical actuator rod or directly. The electrical switch body typically has a multi-pin connector on the back of the column housing. Depress the connector locking tab and withdraw it carefully — do not tug the wiring harness.
Verify each terminal with a multimeter at each key position Reconnect the battery temporarily. With the key in Lock position, BAT should be the only live terminal. Move to Accessory — verify ACC is live. Move to Run — verify IGN1 and IGN2 are both live and ACC has dropped (on many designs) or remains live. Crank to Start — verify ST is live, IGN2 has dropped, and IGN1 remains live. Return to Run and confirm ST has dropped.
Inspect all terminals for heat damage, corrosion, and loose fit Ignition switch terminals that carry sustained current (IGN1, BAT) are prone to heat damage over years of service. Look for melted plastic, discoloured terminals, or terminals that slide forward when a wire is pulled gently. Loose terminals cause voltage drop, intermittent starting, or intermittent loss of instrument cluster power.
Reassemble and verify function before closing up Before refitting steering column covers, verify all four key positions function correctly: Accessory loads work in ACC only, ignition warning lights extinguish in Run, the engine starts in Start, and all loads return to normal in Run after releasing the key. Operate the key through several cycles to confirm.

Specifications

Number of key positions	4: Lock (Off), Accessory, Run (On), Start
BAT terminal supply	12 V DC permanent (directly from battery or main fuse box)
IGN1 availability	Run position AND Start position (does not drop during cranking)
IGN2 availability	Run position only (drops out during Start to shed non-essential loads)
ST terminal availability	Start position only; spring-loaded return to Run on key release
Typical switch current rating	20 A–30 A per switched terminal (varies by manufacturer; heavy-duty applications may be higher)
ACC terminal availability	Accessory position (and Run on some designs); de-energises in Start on most vehicles

Safety warnings

This diagram is a general reference only. Ignition switch terminal designations, pin layouts, and wire colours vary between vehicle manufacturers and model years. Always consult the vehicle OEM service manual for the specific application before any work on ignition switch wiring.
The BAT terminal of the ignition switch is permanently live at battery voltage, even with the ignition off. Disconnect the battery negative terminal before any work on the ignition switch wiring or connector. Accidental short circuits in this area can cause fires or trigger airbag deployment.
Many vehicles route airbag system wiring through or near the steering column in this area. Do not cut, splice, or probe any yellow-sheathed or yellow-connector wiring near the steering column without first consulting the airbag wiring diagram and disarming the airbag system per the OEM procedure.
Never bypass or bridge the ST (starter) terminal directly to the IGN1 terminal. This creates a condition where the starter motor engages whenever the ignition is on, destroying the starter and ring gear rapidly and creating a hazard if the vehicle is in gear.

Tools needed

Digital multimeter with DC voltage measurement
Vehicle service manual with ignition switch wiring diagram
Trim removal tools and panel clips (for steering column disassembly)
Connector release picks and terminal extraction tools
Insulated screwdrivers
Test lamp or circuit probe (for quick live/dead testing)
Wire stripper and crimping tool (if replacing wiring)

Common mistakes

Assuming all 6-wire ignition switches share the same terminal layout — pin positions and wire colours are manufacturer-specific. Using a generic diagram without vehicle verification is a common cause of wiring faults.
Connecting all switched loads to IGN1 and eliminating IGN2 — loads that should drop out during cranking remain energised, causing voltage sag on the ignition system during start and potentially causing hard-starting or failed starts.
Failing to fuse each output circuit independently — the ignition switch is not a substitute for load fuses. Each downstream circuit (ACC loads, IGN1, IGN2) must be individually fused for overcurrent protection.
Routing the ST wire alongside the IGN1 wire without adequate separation — inductive coupling or a chafed insulation fault between these two wires causes the starter to engage unexpectedly.
Working on the steering column without disabling the airbag system — accidental airbag deployment during ignition switch servicing is a serious injury risk.

Troubleshooting

Engine cranks but accessories and instrument cluster go dead during cranking: Cause: IGN2-powered loads are correctly dropping out during Start (normal operation), but if IGN1 loads are also dropping, this suggests a wiring fault, loose BAT terminal connection, or a failing ignition switch contact that drops IGN1 under the high-current draw of cranking Fix: Monitor battery voltage during cranking with a multimeter — a severe drop below 9.5 V indicates an undercharged battery or high-resistance battery cable connection. If voltage is adequate but IGN1 drops, inspect the ignition switch BAT and IGN1 contacts for heat damage or corrosion and replace the switch if contacts are faulty.
Starter engages when key is released to Run position: Cause: Short circuit or mis-wiring between the ST terminal and IGN1 or IGN2 terminal; spring-return mechanism in the lock cylinder failing to fully release from Start position Fix: Disconnect the ST terminal and verify the starter disengages. Check for wiring faults between the ST circuit and any other ignition circuit. Inspect the lock cylinder and key barrel for worn spring-return components that allow the barrel to hang in Start position.
Accessories work but engine will not crank — no click from starter relay: Cause: Open circuit in the ST terminal circuit — could be the ignition switch ST contact itself, the starter relay coil circuit, a neutral safety switch (automatic transmission) or clutch switch (manual) open circuit, or a blown starter circuit fuse Fix: Jump the starter relay trigger terminal directly to 12 V with a jumper wire (engine in Park/Neutral, vehicle stationary). If the starter engages, the relay is good and the fault is upstream in the ST circuit — check the ignition switch ST contact, neutral safety switch, and any inhibitor relays in the start circuit.

Frequently asked questions

What are the 6 wires on a typical ignition switch?

The six wires are: (1) BAT — permanent battery positive, (2) ACC — accessory position feed, (3) IGN1 / Run — primary ignition feed (live in Run and Start), (4) IGN2 — secondary ignition feed (live in Run only, drops out in Start), (5) ST — starter relay trigger (live only in Start), and (6) a secondary accessory, illumination, or ground reference depending on the specific switch design.

Why does IGN2 drop out during cranking?

During engine cranking, the starter motor draws a very high current that can drop battery voltage momentarily to 8–10 V. Loads on IGN2 — such as rear defoggers, HVAC blower motors, or non-essential control modules — are disconnected during Start to prevent this voltage sag from affecting the ECU, ignition system, and fuel injection circuits on IGN1, which must remain stable.

Can I use an aftermarket push-button start with a 6-wire ignition switch?

Yes, but the push-button module must replicate the full 6-wire switching logic — ACC, IGN1, IGN2, and ST positions must all be controlled correctly. Simple relay-based kits that only switch a single Run wire are inadequate for vehicles with IGN2 circuits. Use a module designed for the specific vehicle's terminal arrangement.

What happens if the starter wire (ST terminal) shorts to the IGN1 terminal?

The starter motor would energise every time the ignition is in Run position, grinding the ring gear against the flywheel and potentially destroying the starter's Bendix drive. This is a dangerous and destructive fault. Always check for shorts between ST and IGN1 when installing aftermarket ignition modules or remote start systems.

How do I identify which terminal is which on an unmarked ignition switch?

Use a wiring diagram from the vehicle service manual. If unavailable, use a multimeter in continuity mode with the key removed (Lock position) — BAT should be permanently live. Step through each key position and map which terminals gain voltage. Cross-reference with a circuit diagram for the switch part number if marked on the switch body or documentation.

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