Why fit a fuel flow sensor?
Injector duty tells you what the ECU is asking for. A flow sensor tells you what is really being delivered. With one wired in, the Elite can report live fuel flow and keep counters for fuel used, trip fuel used and seasonal fuel used. For endurance racers that means knowing when to pit. For street cars it's a quick way to see what a tune change did to consumption.
The function is set up across four tabs in ESP: Wiring, Calibration, Display and Diagnostics.
Wiring tab
Pick the input the sensor is wired to. You have two choices.
| Input | When to use it | Pull-up available |
|---|---|---|
| AVI (Analog Voltage Input) | The preferred choice | 1k ohm to 5V |
| SPI (Synchronised Pulsed Input) | When you've run out of spare AVIs | Weak 10k ohm to 5V |
If you use an SPI, set its Sensor Type to Hall Effect.
Should the pull-up be on?
The pull-up gives a two-wire sensor something to pull against. The general rule:
- Enable it for a simple two-wire sensor that has no supply of its own.
- Disable it for a sensor with its own power feed.
- Disable it if the sensor is shared with another ECU, as in a piggyback install with the factory computer still connected. That ECU normally supplies the pull-up already, and adding a second one skews the reading.
Check the sensor maker's wiring information to see which category yours falls into.
Calibration tab
The Elite has to know how the sensor's signal translates to flow. ESP ships with a set of ready-made calibrations. Load one with the yellow folder (Open) icon at the top left of the tab. If your sensor isn't included, build a calibration from the manufacturer's data sheet, then save it with the blue disk icon so you can reuse it on the next car.
Once calibrated, sanity check the reading. Run the engine at a steady load for a set time and compare the fuel used counter against what came out of the tank, or against expected injector flow. Big differences usually mean the wrong calibration.
Display tab
Warning Minimum and Warning Maximum make any fuel flow gauge or readout in ESP flash red when flow goes below or above the values you set. They are visual only and don't change how the engine runs. We set the minimum just under a normal idle reading and the maximum a little above what the engine uses at full power, so a flashing gauge means something has genuinely changed.
Diagnostics tab
These settings look at the raw sensor voltage to catch wiring faults.
| Setting | Trips when | Code | Default |
|---|---|---|---|
| Raw Min | Voltage drops under the value you set | P0003 | Disabled |
| Raw Max | Voltage rises above the value you set | P0004 | Disabled |
A reading stuck at either end almost always means a short or an open circuit. If Engine Protection is enabled, you can give either fault a DTC severity so the ECU reacts rather than just logging it. To pick good limits, log the sensor's voltage across idle and full load and set the thresholds safely outside that range.
Troubleshooting
| Symptom | Usually |
|---|---|
| Reads zero with the engine running | Wrong input selected, no power to the sensor, or an open circuit |
| Reads a fixed high value | Signal shorted to 5V or 12V, or pull-up enabled on a sensor that doesn't want it |
| Reading moves but is clearly wrong | Wrong calibration loaded |
| P0003 or P0004 logged | Check connectors and wiring first, then the Raw Min/Max limits |
The same pull-up and diagnostic logic applies to most Elite sensors, including the fuel pressure sensor. For a list of codes, see the DTC index.
