What dash I/O sharing does
Haltech display dashes have their own analog inputs and switched outputs, meant for things the dash handles by itself. When the dash is configured in NSP, those same pins can be handed to the ECU instead. The ECU sees them as extra inputs and outputs, reads and drives them over the Haltech CAN bus, and you assign them to ECU functions exactly like its own pins.
This is most useful on ECUs with a modest pin count. An Elite 550, for example, fills up quickly on a turbo build with boost control, fans and a few extra sensors. Adding an iC-7 or uC-10 you were going to buy anyway gives you more room without a separate expander box.
This only works on dashes that are configured in NSP. An iC-7 still running the older ICC software needs updating to NSP first. Platinum Sport, Platinum Pro and the rest of the Platinum family can't use this feature at all.
Firmware you need
Both ends need firmware new enough to support it. Update before you touch any settings, because the options simply won't appear on older versions.
| Device | Minimum firmware |
|---|---|
| Nexus ECU or VCU | 1.26.4 |
| Elite ECU | 3.11.0 |
| iC-7 dash | 2.26.3 |
| uC-10 dash | 2.26.3 |
Setting it up in NSP
You'll connect NSP to each device in turn, because the dash and the ECU each have their own half of the setting.
- Get both devices on the Haltech CAN bus. The dash has to be sourcing its data from the Haltech ECU over CAN. If that isn't done yet, follow sourcing data for dashes in NSP first.
- On the dash: connect NSP to the dash and open Connections > CAN > Haltech CAN System. Turn on External IO Control. The dash has to restart for this to take effect, so use the reboot button in NSP or cycle the key off and on.
- On the ECU: disconnect from the dash and connect NSP to the ECU. In the same place, Connections > CAN > Haltech CAN System, enable Dash and pick the model of dash you have. Restart the ECU the same way.
- Check the result. Open the ECU's I/O report. The dash's pins should now be listed there alongside the ECU's own, ready to assign.
If you're new to working with dashes in NSP, navigating dashes in NSP is a good primer.
The one rule that trips everyone up
A pin can only belong to one device. If the dash is already using an input or output for one of its own functions, the ECU won't see it as free. Before assigning a dash pin in the ECU, connect to the dash and disable whatever dash function is using that pin. In the ECU's assign list, a usable dash pin shows as available and not configured on the external device.
Example: a sensor on a dash input
Say you want to add a 3-wire fuel pressure sensor and the ECU has no spare analog inputs. Wire the sensor's signal to a dash analog input such as AVI 2, with its supply and ground taken from the dash as shown in your dash's pinout. Then:
- Confirm on the dash that nothing is assigned to AVI 2.
- Connect NSP to the ECU and enable the sensor's function.
- Go to the function's Wiring node, click Assign and choose Dash AVI 2.
- Set the sensor calibration and pull-up the same way you would on an ECU input, then restart the ECU when NSP asks.
Once both devices are back online, the ECU reads the sensor as its own channel. It can log it, use it in protection strategies and send it back to the dash to display, just as if it were wired to the ECU. The same process works for an oil pressure sensor or any other analog input function.
Example: an output on a dash DPO
Outputs need more thought than inputs, for two reasons.
- Current limit. Dash outputs switch to ground and can sink a maximum of 3 A. Plenty of loads draw more than that.
- Power source. If you power a device from the same feed as the dash, you're drawing from the CAN power supply (+12V). That supply may not be able to deliver what a motor or pump needs.
The answer for anything heavier than a small indicator or solenoid is a relay. The dash output switches the relay coil to ground, and the relay's contacts feed the load from its own fused supply straight from the battery. See how relays work and why you need one if that's new ground.
As an example, here's how we'd run a transmission cooler fan from a dash output using one of the ECU's spare thermo fan functions:
- Wire the relay coil between switched +12V and dash DPO 1. Wire the fan through the relay contacts, fused, from the battery.
- Make sure DPO 1 isn't assigned to anything on the dash.
- In the ECU, enable a spare thermo fan function, go to its Wiring node, Assign it, and pick Dash DPO 1.
- Set the active state to Low. DPOs pull to ground when on, and the relay coil needs that ground to energize.
- Back in the function, choose the temperature channel it should follow and set the on and off points. Leave a few degrees between them so the fan isn't cycling constantly.
Settings summary
| Setting | Where | Our advice |
|---|---|---|
| External IO Control | Dash: Connections > CAN > Haltech CAN System | Turn on, then restart the dash |
| Dash (and dash model) | ECU: Connections > CAN > Haltech CAN System | Pick the exact model, then restart the ECU |
| Dash AVI / Dash DPO | ECU: function Wiring node, Assign | Free the pin on the dash first |
| Active state | ECU: output wiring | Low for ground-switched relays |
Troubleshooting
| Symptom | Usually |
|---|---|
| No dash pins in the ECU's assign list | Firmware too old on either device, one side of the setting not enabled, or a device not restarted |
| A particular dash pin isn't offered | The dash still has a function assigned to it |
| Sensor reads wrong | Calibration or pull-up setting in the ECU doesn't match the sensor |
| Output works for a moment, then the device misbehaves | Load too big for the 3 A output, or the CAN supply is sagging. Add a relay and a separate feed |
| Output does the opposite of what you expect | Active state set wrong for how the relay is wired |
FAQ
Does this work with a Platinum ECU?
No. Sharing dash I/O is supported on Nexus and Elite ECUs only, at the firmware versions above.
Can I still use the dash inputs for dash functions?
Yes, just not the same pin for both. Any pin the dash keeps for itself stays with the dash, and the ECU can use the rest. Because the ECU broadcasts its channels, a sensor the ECU reads through the dash can still be shown on the dash.
Should I use a dash or a dedicated expander?
If you need a couple of extra pins and already want a Haltech dash, dash I/O is the neat answer. If you need a lot of I/O or high-current outputs, a proper expansion module or a bigger ECU is usually better. Book a free consultation and we'll help you work it out.
