I need the help of someone who knows electronics (engineer maybe?!)

[GhostlyCoupe]

I've been struggling with an ECU issue with a chipped ECU for my SR20DET and have narrowed it down.

Basically it's only driving the knock sensor circuit at 3.3v (tested with PIN 27 depinned from the ECU) which is causing a Code 34 Knock Sensor malfunction light. The reference voltage is supposed to be 5v so of course the ECU is registering a short and throwing the code and retarding my timing.

So what I want to know is what's a safe way to connect a 5v source to this circuit without blowing up the ECU? I'm not a wiz when it comes to these kind of integrated circuits so I thought I'd ask first.

[GhostlyCoupe]

Some additional helpful info from someone I was discussing this with:


It's actually one wire. The knock sensor circuit is a +5v wire that grounds through the sensor itself .. the resistance of the sensor alters the voltage level (supposed to be steady around 2.5v with the resistance of the sensor included in the circuit).

Yeah it's 3.3 that's the whole problem. It's supposed to be 5v. Apparently this is a fairly common issue with modified ECU's (at least Nissan ones)

Right now with the resistor (knock sensor) installed it reads 1.84 volts which is why it's throwing the code INSTANTLY. It should be 2.5v - 3.0v . The resistance of the sensor is a constant 560k OHMs so when the starting voltage is incorrect at 3.3 .. I'm sure you can see why the ECU is thinking there's a short and throwing the code as it expects a final voltage of around 2.5v with the sensor plugged in.

I'm sure how the ECU reads knock is more complex, but the ECU self-checks the circuit by looking for an open or a short.. that's it. If voltage is above or below the expected value it throws it.

[Om1kron]

The oem knock sensor is fucking useless. Have you tried going to an electronics store and grabbing a resistor that will report whatever it is you need to the ecu to rid it of that code.

I currently run a 1hz 1ohm resistor in my female knock sensor plug and I've never had a problem with code 34 popping up ever again. The car has ran like a champ for the last three years give or take other electronic misgivings but at least I've eliminated that aspect.

[GhostlyCoupe]

Yeah I tried that but because the initial voltage is incorrect, the ECU still throws code 34 even with a plain resistor hooked up (expected voltage is still below the set threshold, used 1M Ohm resistor)

[GhostlyCoupe]

EDIT: I'd also be happy to turn the POS off if someone can point me to how to do it using NDS, NISTune, whatever

(Programmable Daughterboard installed)

[reflexdb]

Ghostly - Can you find another 5V source pin on the ECU and use that instead? Power circuits are designed to handle a limited amount of current, but a resistance type sensor isn't going to draw much current. So, find another 5V source for another sensor, and use that for the knock sensor as well. That would also be a great sanity check to verify that getting 5V to the knock will fix your problem.