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Ok here is a strange question.

Helping a friend setup a remote logging unit and it is proving to be a pain in the bum.
Using the GM water and air 2 wire sensors we need to add a resistor to them on the 5 volt line to be able to add another wire as a signal wire.

Now my question is, does the DELCO run a resistor on board to do this function and if so can anyone tell me the EXACT value of said resistor ???


Cheers Baz

Well the workshop manual specifies that @20 deg C both sensors should be 3,400 ohms and @100 deg C they should be 185 ohms. The air temp should be 1800 ohms at 38 degrees so that would be suitable and the coolant value for 100 deg or maybe a little higher say 220 ohms would be a reasonable point to work with. Just pick resistors close to these values.

Which Delco computer are you talking about? Im pretty sure there will be, someone will need to measure it. It is a strange request, I assume you have your reasons for approaching it this way.

Ludis of the old http://cruzers.com/~ludis/ site had schematics, but I cant find them online from other sources now. It appears that information was collected or created in around 1998-2000.

Ive put a mirror up at https://pcmhacking.net/ludis/

The information you need can probably be found under the '165 schematic, inputs page and which is now available here:

https://pcmhacking.net/ludis/1227165schematic.html

Note that a '165 is the same as an '808 but without the SXR comms chip.

Thanks for the links Antus I will have a look.

He is using the standard 2 wire GM water temp sender and a the VR 2 wire air temp sender.

We can set up a calibration file to convert the temps using a basic 1k Ohm resistor.
I just thought is anyone knew what they used in the Delco I could cheat and use that and it all should be pretty close!!.

It sounds like your trying to add an external logger in addition to the computer. Is there a reason you cant log the temperature data from the computer and leave the wiring stock?

Sorry I misread what your trying to do.

You cant piggy back existing sensors with another pullup resistor. Will mess up the ECU readings. The '165 uses two pullups on the coolant sensor to get good resolution at both hot and cold temps by switching between them at a certain coolant temp - schematic antus posted shows this and the values.

Not knowing the car, the sensor outputs are likely these..
Coolant - http://pe-ltd.com/assets/coolant_temp.pdf
Manifold Air Temp - http://pe-ltd.com/assets/air_temp.pdf

No piggy back, all the sensors are separate to the ECU.