How this connector is laid out
It helps to see the 34-pin plug in groups rather than as a list of numbers:
- Power and ground: two battery grounds, the switched ignition input and the injector power input.
- Sensor supplies: regulated +5V and +8V feeds for sensors.
- Injectors: eight current-controlled injector drivers.
- Ignition: six logic-level ignition outputs.
- Analog inputs: five AVIs, including the ones Haltech's harness uses for MAP and TPS.
- Digital outputs: DPOs for things like the fuel pump relay and engine control relay.
- Stepper: four pins for a stepper idle motor, which can double as general outputs.
Elite 2500 34-pin pinout
| Pin | Function | Wire color | What to know |
|---|---|---|---|
| 1 | DPO 2 | Violet/Brown | Switches to ground, 1 A max; fixed 5V pull-up |
| 2 | AVI 4 | Orange/Yellow | 0-5V analog input; selectable 1k pull-up |
| 3 | IGN 1 | Yellow/Black | Ignition output, 1 A max |
| 4 | IGN 2 | Yellow/Red | Ignition output, 1 A max |
| 5 | IGN 3 | Yellow/Orange | Ignition output, 1 A max |
| 6 | IGN 4 | Yellow/Green | Ignition output, 1 A max |
| 7 | IGN 5 | Yellow/Brown | Ignition output, 1 A max |
| 8 | IGN 6 | Yellow/Blue | Ignition output, 1 A max |
| 9 | +5V sensor supply | Orange | 100 mA max total |
| 10 | Battery ground | Black | Straight to the battery negative terminal |
| 11 | Battery ground | Black | Straight to the battery negative terminal |
| 12 | +8V supply | Orange/White | 100 mA max total |
| 13 | 12V ignition input | Pink | Must be live with the key on and while cranking only |
| 14 | AVI 10 (TPS) | White | 0-5V input; 1k pull-up switchable in software |
| 15 | AVI 9 (MAP) | Yellow | 0-5V input; 1k pull-up switchable in software |
| 16 | AVI 2 | Orange/Black | 0-5V input; 1k pull-up switchable in software |
| 17 | AVI 3 | Orange/Red | 0-5V input; 1k pull-up switchable in software |
| 18 | DPO 1 | Violet/Black | Switches to ground, 1 A max; pull-up is user definable |
| 19 | INJ 1 | Blue | Current controlled, 0-8A peak, 0-2A hold |
| 20 | INJ 2 | Blue/Black | Current controlled, 0-8A peak, 0-2A hold |
| 21 | INJ 3 | Blue/Brown | Current controlled, 0-8A peak, 0-2A hold |
| 22 | INJ 4 | Blue/Red | Current controlled, 0-8A peak, 0-2A hold |
| 23 | DPO 3 | Violet/Red | Switches to ground, 1 A max; fixed 12V pull-up |
| 24 | DPO 5 (fuel pump trigger) | Black/Yellow | Switches to ground, 1 A max; fixed 12V pull-up |
| 25 | DPO 6 (ECR out) | Black/Red | Switches to ground, 1 A max; fixed 12V pull-up |
| 26 | ECU injector power input | Red/Blue | 12V from the injector power relay; the ECU won't run without it |
| 27 | INJ 5 | Blue/Orange | Current controlled, 0-8A peak, 0-2A hold |
| 28 | INJ 6 | Blue/Yellow | Current controlled, 0-8A peak, 0-2A hold |
| 29 | INJ 7 | Blue/Green | Current controlled, 0-8A peak, 0-2A hold |
| 30 | INJ 8 | Blue/Violet | Current controlled, 0-8A peak, 0-2A hold |
| 31 | Stepper 1 P1 / DPO | Green | High or low side driver, sources or sinks up to 1 A |
| 32 | Stepper 1 P2 / DPO | Green/Black | High or low side driver, sources or sinks up to 1 A |
| 33 | Stepper 1 P3 / DPO | Green/Brown | High or low side driver, sources or sinks up to 1 A |
| 34 | Stepper 1 P4 / DPO | Green/Red | High or low side driver, sources or sinks up to 1 A |
Wire colors are listed as main color/stripe, matching Haltech's harness abbreviations (V/BR is violet with a brown stripe, L is blue, and so on).
The pins that catch people out
Pin 26: injector power input
This isn't optional. The ECU needs 12V here from the injector power relay to operate at all. If an Elite 2500 powers up on the laptop but won't fire injectors or run, check pin 26 first.
Pin 13: ignition input
Feed it from a circuit that's live in the run and crank positions only, never an accessory circuit that drops out while cranking.
Pins 10 and 11: grounds
Run both straight to the battery negative, not to a body or chassis point. Poor grounds cause noisy sensor readings and trigger errors that are painful to chase.
Pins 9 and 12: sensor supplies
Each rail is rated at 100 mA. That's plenty for sensors, but it isn't a power source for relays or accessories.
Ignition outputs
IGN 1 to 6 are logic-level outputs, rated at 1 A. They're meant to drive coils with built-in igniters or an external igniter, not the primary winding of a dumb coil. If your coils need an igniter, look at an HPI4 or larger.
DPO pull-ups
DPOs switch to ground. The pull-up only matters when the output feeds a signal input rather than a relay coil; pins 23 to 25 have a fixed 12V pull-up, pin 1 a fixed 5V one, and pin 18 lets you choose.
FAQ
Can I use the stepper pins as normal outputs?
Yes. If you don't have a stepper idle valve, pins 31 to 34 are available as DPOs, and they can drive high or low.
Where's the rest of the I/O?
The Elite 2500 also has a 26-pin connector. See the 26-pin main connector, the 34-pin premium harness page, and the Elite 1500/2500 quick start guide.
Need the connector face diagram? Ask us and we'll send it over with advice for your build. Shopping for the ECU itself? Here is the Haltech Elite 2500.
