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kb58
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GM vs Continental Fuel Composition Sensor - Ethanol E85

The Infinity User's Manual states that a GM 12570260 Fuel Composition Sensor must be used to sense % ethanol. This sensor is very expensive, running about $350-400.

Other aftermarket ECUs are using the Continental sensor, 13577394, available new for well under $100.

Can the cheaper Continental unit be substituted in place of the GM part and is the signal scaling the same?

AEM_SS
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Yes

Yes

TimeAttackS2K
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I recently picked up a

I recently picked up a Continental 13577394 sensor and have a wiring question.  

Does this sensor use +12v/GND?  Or, +5v/Sensor GND?  I've seen conflicting info about this sensor... Some are saying 12v, while others are saying 5v. 

 

AEM_SS
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+12V

+12V

EGbeater
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I'm using the Continental

I'm using the Continental 13577379 flex fuel sensor (OEM application: 2012-2013 Cadillac SRX)—which is the same sensor unit as the 13577374, just with shorter 3/8" OD tubes for the fuel inlet/outlet—with a 30-3508 P&P harness with my Infinity 6 (30-7106) on my Honda S2000.

I connected Deutsch pins 3 and 8 of the P&P harness to the ground and 12+ pins of the 13577379 sensor, and Deutsch pin 9 to the sensor pin marked "Out."

In checking my wiring work with a multimeter before actually plugging the molex to the flex fuel sensor, with the ignition key on (but without the engine started and running), I confirmed 12+ and ground but was surprised to see 12+ also coming out of the wire connected to Deutsch pin 9 ("Digital_In_3 / Flex Fuel Sensor (Hz)").

Is this normal/correct? If not, I don't want to plug in the connector and fry the sensor or worse, the Infinity.

The aux connector pinouts from the instructions for my 30-3508 harness are below.

kb58
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Yes it's normal, you''re

Yes it's normal, you''re seeing the +12V being fed back from the ECU pullup resistor (this is true of all similar Infinity inputs). The sensor itself can only pull to ground, it cannot supply an actual output voltage.

Aleo24
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While looking into wiring of

While looking into wiring of the continental sensor (same as haltec) i found that people would get erronous values if it was connected to sensor grounds and was recommended to ground the sensor at the bracket i used to mount it. I have had 0 issues with my fuel flex which works amazing.

kb58
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That's correct, don't connect

That's correct, don't connect anything to signal ground that you don't have to. I had that exact problem, as I had connected the power ground of the GM flex sensor to signal ground and it caused instability in nearly all my readings. Ground it to the sensor's mounting bracket.

EGbeater
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Interesting, thanks for the

Interesting, thanks for the feedback / info on the potential ground issue, Aleo24 and kb58. My flex fuel sensor isn't mounted to a steel bracket, so perhaps ground it to the closest chassis point possible (with the shortest wire possible)?

Also, has anyone had any issues with the flex fuel sensor's output due to bubbles in the return line (or possibly vibration) confusing the sensor, as described in this Supra forum thread?

http://www.supraforums.com/forum/showthread.php?927713-Most-Common-Flex-...

 

kb58
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Well, you definitely want to

Well, you definitely want to orient it such that it's not at a high point where bubbles can get stuck in it. Aside from that though, if there are bubbles in the fuel, that's bad news for the engine, as those same bubbles would be going through the injectors and causing momentary leanness. If it's oriented correctly and you still think bubbles are a problem, you'll have to investigate things upstream, like where the fuel is picked up and how it's returned to the tank. Maybe the fuel is splashing near the filter sock and getting sucked into the pump.

The instability I've seen with the GM sensor seems to be pressure and/or flow related. It happens enough that AEM takes a snapshot of the reading and freezes it above some MAP value.

EGbeater
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I probably should have

I probably should have clarified that my flex fuel sensor is installed in the return line back to the tank, not in the feed line to the rail. I obviously induced some air bubbles by disconnecting the return line to install the sensor (and a bunch of gas leaked out when I did this), but I assumed the air pocket would clear itself out after firing up the car and idling it... I've testdriven the car since installing the flex fuel sensor (to check for any fuel leaks at engine speeds higher than idle) and the car seems to drive normally.

bry195
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the sensor ground on stock

the sensor ground on stock BMW wiring harnesses usually is in a star configuration meaning it terminates with all the other grounds to the chassis. does this mean we have to remove the sensor ground temination point to the star?