GM sensor 12685371 (4 pin combination oil pressure and oil temp)

Hi all,

I'm looking for calibration data for a newer GM oil pressure and temp sensor (12685371) It's used on late model GM engines, mostly trucks. It's a 5v sensor, and I'd like to use it since it combines both oil pressure and temperature into one sensor. Anybody got any calibration data for it? thanks!

Here's another question then: anybody out there have a decent method of calibrating a sensor? Use boiling water for temp, and compressed air for pressure?

Gauge Pressure is relatively easy as you only need two points to build a calibration, so you can get a METAR from your local airport to set the ambient pressure point and then by comparing with a known pressure source, set the upper point. If you cannot generate the pressure needed for the full range, you can extrapolate the data out. Absolute Pressure requires a vacuum source to generate below atmospheric values for testing. I use a Druck DPI610E to do pressure sensor testing and calibrations.

Temperatures are harder as they are a non linear curve, so you need more data points, I have access to an environmental test chamber that allows for sensor to be run between -30° and 140° in a linear ramp over 2 hours, doing this, I log the voltage out of the sensor and compare it against a couple of known good sensors in the test loom. This lets me generate a calibration of temperature versus voltage in 10° steps.

You can validate a calibration for a fluid sensor using water going through its phases, but you need to have it in a steady state and have enough dwell time for the sensor to read correctly.

Thanks Stephen. Doing some experiments validates what you say: it's important to hold the temperatures steady with enough dwell time to get reproducible readings.

One thing you mention is that you're calibrating with voltage, whereas I've been measuring resistance. Does that matter?

Hi John, It depends on the way that the device that you are doing the calibration for loads the calibrations. The MoTeC calibrations are in voltage, so it is more practical to just read the voltage on the input pin to make the calibration. Other devices that use a resistance value for the calibration will need to have the resistance table built. It is also easier to read a voltage signal.

Thanks Stephen. Your advice was helpful: I used my freezer, refrigerator, and oven to achieve and hold temps from -20 to 140 and I got reproducible ohm readings. Now to work on the pressure side.

And... if anybody wants the calibration data, drop me a DM. Happy to share. No benefit to me to keep it a secret, lol.

John,

I don't think the HPA forum has DM capabilities - or I've never been able to find them. Would you mind posting the Calibration data you've come up with.

I have a contact in the Automotive industry who has reached out for a data sheet from Delphi, but no response as of yet. I'll share as soon as I have one

Thanks

Paul

Hi Paul,

Sorry for the imperial units -- the car is a 67 Chevy Nova with a Holley Dominator ECU.

This is the oil temperature calibration (again, sorry for the Fahrenheit):

John,

Thanks for the data. I use Imperial settings also, I'm located in Saint Louis, USA.

Do you have any data on the pinout?

Paul

Hi Paul,

Pinout is 1 = 0v (sensor ground), 2 = pressure signal, 3 = 5v, 4 = temp signal. I got that from a GM source. You can get a connector at Ballenger Motorsports here:

Home » Shop » Connectors / Harnesses » Delphi / Packard » Connector Kits » 4 Way Connector Plug Kit for C7 Corvette oxygen sensor, Black

John