What the neutral switch is for
A neutral switch reports when the transmission is out of gear. On an automatic it's usually a park/neutral position switch, and its classic job is to stop the engine from cranking unless the shifter is in Park or Neutral. Many of these switches do more than that, feeding gear position and reverse light information too.
For the Elite, knowing the car is in neutral is useful well beyond starting. It's a handy channel to log, and a clean condition to reference when you set up other functions. Wiring it takes a few minutes, and the only real decision is which kind of input to use.
Choosing an input: SPI or AVI
On the Wiring tab, pick the Neutral Switch Input. Either a synchronized pulsed input (SPI) or an analog voltage input (AVI) will work.
| SPI | AVI | |
|---|---|---|
| Best for | Simple switches that either ground the wire or feed it voltage | Switches with in-between voltages, or when you're out of SPIs |
| You set | Edge, sensor type and pullup | An On voltage and an Off voltage |
| Watch out for | Choosing the wrong edge flips the logic | Thresholds set too close together can chatter |
Setting up an SPI
| Setting | What it does | Our advice |
|---|---|---|
| Edge Select | Decides which kind of switching counts as "on" | Falling if the switch connects the wire to ground when in neutral. Rising if the switch supplies voltage to the wire when in neutral. |
| Sensor Type | How the input conditions the signal | Hall Effect, which is correct for every switch input |
| Pullup | Gives the wire a voltage to sit at while the switch is open | Enable it for a ground-switching switch. Without it, the wire floats when the switch is open and the reading is unreliable. |
Ground-switching is the arrangement we run into most, so Falling with the pullup on is the setup we use most often.
Setting up an AVI
An AVI reads the actual voltage, so you need to tell the Elite where "on" and "off" are. There are two thresholds:
- Switch On Voltage: once the input passes this voltage, the switch is treated as on.
- Switch Off Voltage: once the input passes back through this voltage, the switch is treated as off.
The gap between them is deliberate. Real wiring has a bit of noise and voltage drop, so you don't want a single trigger point that the signal can dither around. Put each threshold a safe distance inside the switch's real on and off voltages, and leave space between them. That gap gives you hysteresis, so the reading snaps cleanly from one state to the other.
Worked example: ground-switching switch
Say your switch sits at about 5 V when the car is in gear and gets pulled to about 0 V in neutral. We'd set the On voltage to 0.8 V and the Off voltage to 4.2 V. The input has to fall below 0.8 V to read as neutral, then climb back above 4.2 V before it reads as in gear. A little ground offset or a sagging supply won't cause a false change.
Worked example: voltage-switching switch
Now say the switch works the other way: it rests near 0.5 V in gear and rises to around 5 V in neutral. Here the On threshold sits above the Off threshold, for example On at 3.8 V and Off at 1.5 V. The input has to rise above 3.8 V to switch on, and drop below 1.5 V to switch off.
Before you pick numbers, watch the raw input voltage in ESP while moving the shifter through every position, with the engine off and again with it running. Charging voltage and electrical noise can shift the readings. Set your thresholds around what you actually see.
Troubleshooting
| Symptom | Usually |
|---|---|
| Shows neutral when in gear, and the reverse | Wrong edge selected on an SPI, or On and Off voltages swapped on an AVI |
| Status flickers | AVI thresholds too close together, or a floating input with no pullup |
| Never changes state | Wrong input assigned, pullup missing on a ground-switching switch, or a broken wire to the switch |
| Works with the engine off but not running | Electrical noise or charging voltage pushing the reading past a threshold. Widen the gap. |
Neutral switch FAQ
Can the Elite stop the car from cranking in gear?
On most cars the factory neutral safety switch does that directly in the starter circuit. Keep that circuit intact, and use the Elite input as information on top of it. If you want the ECU to manage starting, look at the start/stop button setup.
Do manual cars need a neutral switch?
Many manuals have one on the gearbox, and it's worth wiring in. Pair it with a clutch switch for even better logic.
Where's the Nexus version of this page?
See the Nexus neutral switch article. For full gear information, the gear detection function is the next step. Questions about your transmission? Contact us.
