Why monitor crankcase pressure?
A healthy engine keeps its crankcase close to a steady, predictable pressure. The PCV or breather system handles the normal blow-by that gets past the rings. When that balance changes, it's telling you something: worn or broken rings, a blocked breather, a turbo seal pushing oil pressure into the sump, or on a diesel, fuel leaking into the oil and building pressure. Haltech calls out that last one specifically as a common cause of overpressure, and it can do real damage if it goes unnoticed.
The Elite's crank case pressure function lets you watch this channel in logs, get an on-screen warning when it goes too high, too low or swings around, and tie it into engine protection so the ECU can act on it.
Wiring the sensor
On the Wiring tab, pick the input the sensor is connected to. Two input types are allowed:
| Input | When to use it | Settings to check |
|---|---|---|
| AVI (analog voltage input) | The recommended choice | Pull up: switches in a 1k resistor to 5V |
| SPI (synchronized pulsed input) | Only when you've run out of free AVIs | Sensor Type: set to Hall Effect for any analog sensor. Pull up: a weak 10k resistor to 5V |
Pull up on or off?
This is the setting people get wrong most often. The rule is simple:
- Two-wire sensors (like most temperature sensors) have no power supply of their own and need the pull up enabled.
- Sensors with their own supply, which includes the typical three-wire pressure sensor with 5V, ground and signal, should have it disabled.
- Shared sensors: if another ECU also reads the same sensor, for example the factory ECU in a piggyback install, that ECU usually already provides the pull up. Set the Elite's to disabled.
A pressure sensor with the pull up wrongly enabled will read, but the reading will be skewed, and that's worse than an obvious fault because you might believe it.
Calibration
The Calibration tab is where you tell ESP how to turn the sensor's voltage into pressure. A library of calibrations installs with ESP. Click the open-folder icon to load one, and the disk icon to save your own. If your sensor isn't in the list, create a custom calibration from the voltage and pressure points on the manufacturer's data sheet.
With the engine off and the crankcase vented to atmosphere, the reading should sit at atmospheric pressure. If it doesn't, you have the wrong calibration, the wrong pull up setting, or a wiring problem.
Warnings and gauge range
The Display tab controls what you see in ESP, not how the sensor is read:
| Setting | What it does | Our advice |
|---|---|---|
| Warning Minimum | Crank case pressure gauges in ESP flash red below this | Set it just under the lowest pressure you see in healthy logs |
| Warning Maximum | Gauges flash red above this | Set it just over the highest healthy value, including under full load |
| Display Minimum | Bottom of the gauge scale | Pick a range that makes normal variation easy to see |
| Display Maximum | Top of the gauge scale | Same, with enough headroom to show a problem clearly |
The display limits only change what gauges can show. They don't clip the actual sensor reading in logs or protection logic.
Diagnostics and engine protection
The Diagnostics tab turns this sensor into a safety system. Every check below is off by default. Each one sets its own code, and if the Engine Protection function is active you can give it a severity level so the ECU responds.
| Check | Code | Catches |
|---|---|---|
| Raw Min | P1694 | Signal voltage under your limit, pointing to a short or an unplugged sensor |
| Raw Max | P1695 | Signal voltage over your limit, another wiring fault indicator |
| Operating Min | P1696 | Crankcase pressure below your set level |
| Operating Max | P1697 | Crankcase pressure above your set level |
The raw checks tell you the sensor has a problem. The operating checks tell you the engine might. Keep that distinction in mind when you pick severities. A wiring fault on a monitoring sensor rarely justifies pulling power, while a sustained overpressure reading on a healthy sensor might.
Our approach: log several normal drives and pulls first, find the real operating range, then set operating limits with a sensible margin outside it. Start with a warning-level response, and only step up to stronger protection once you're confident it won't trip on a healthy engine.
Troubleshooting
| Symptom | Usually |
|---|---|
| Reading pinned at one end, P1694 or P1695 set | Open or shorted signal wire, missing 5V supply, or wrong input selected |
| Reads, but offset from atmospheric with the engine off | Wrong calibration, or pull up enabled on a powered sensor |
| Pressure climbing over time on a diesel | Check for fuel in the oil |
| Pressure rises sharply under boost | Blow-by past the rings, a restricted breather, or turbo oil seal issues |
FAQ
Can I use an SPI if my AVIs are full?
Yes. Set the sensor type to Hall Effect and choose the pull up based on the sensor, just like an AVI.
Will a warning actually protect the engine?
The Display tab warnings only flash in ESP. For the ECU to act, enable the Diagnostics checks and set a severity with Engine Protection turned on.
Related setups: oil pressure and engine protection, the coolant pressure sensor and the barometric pressure sensor.
