2012 GMC Terrain Fuel Composition Sensor ERROR

[LaszloT]

Sensor reports water in fuel, although tech testing reveals high ethanol content instead - 18%, vs. the max 10% that should be in Regular petrol.

If this customer lives near the U.S. border and shops in Maine as well, how would you suspect that they got an unusually high content of ethanol in their fuel? Are there any know fuel diluting practices that might cause this?

It has a 2.4 L 4-cyl DOHC w/variable valve timing direct-injection engine, with specs at this link:

http://www.carseverything.com/259/2012-gmc-terrain-performance-specs.html

[TrevorH]

Isn't the fuel grade / mix done at delivery (or at the pump)? It could have been an error during either of those. I'd back track with samples from the gas station tank, gas pump from the station, and possibly earlier in the distribution channel. If you were going to dilute the fuel, I would think you'd use something that's cheaper than gas to produce. That would probably rule out ethanol for intentional dilution.

Temporary fix for the customer is to do a half tank fill up (assuming there's room) of Shell 91 which has no ethanol. Assuming it mixes, that should drop the ethanol to ~9%. There may also be other brands have a non-ethanol choice.

[LaszloT]

Fuel grades are blended at the bulk petroleum distribution terminal, as the fuel is loaded onto trucks. Ethanol is injected into the gasoline fuel flow as it pumped into tanker trucks.

In general, only Regular (10% ethanol - E10) and Premium (E0) are stored and shipped, and Midgrade is blended at the gas station pump to make E5. This reduces the number of tanks required.

[TrevorH]

I knew you'd be the right person to ask. :)

[LaszloT]

I want to know if there is any fuel dilution fraud scams that might be responsible for this, either here or in Maine (USA).

[STeveD]

I'm guessing there's a customer who filled up at your station who wants CanTire to pay the $193 bill?

Not sure how they do it ... if E85 has a completely separate pump/hose from E10 gasolines... But there's almost 2L of product left in the hose, filter, etc. from the previous customer. So if you were empty, and put only 10L of regular gas in your tank, 20% of that could be the product that the previous customer filled. That would give you 17% ethanol.

Supposedly, Maine has no E85 at the public pumps.

Ask the dealership what test procedure was used and for a print-out of the complete fuel analysis and procedure that they used. I'm not a spelling nazi, especially when people don't speak English as a first language, but I can't put my faith in a test result where the technician can't even spell Ethanol.

"In God we trust, all others bring data." - W. Edwards Deming

Maybe, because of their E85 compatible engines... they have special testing equipment at the dealership. No clue.

[STeveD]

See if a GM dealer will tell you what these TSB's are about:

http://www.automd.com/tsb/bulletin_b325190/
http://www.automd.com/tsb/bulletin_b326792/

[LaszloT]

ERROR Codes

1. P0179 Fuel Composition Sensor Circuit High Frequency

This is a failure code for a fuel composition sensor and man are they proud of these sensors. Last time I put one on the price for the sensor was almost 500.00. This does usually not cause a driveability problem. Here is a circuit description

Alcohol content and fuel temperature information is supplied to the powertrain control module (PCM) from the fuel composition sensor (FCS). The FCS has an ignition 1 circuit, a signal circuit, and a ground circuit. The FCS uses a microprocessor inside the sensor to measure the ethanol percentage and fuel temperature, and changes output signals accordingly. The signal circuit carries both the ethanol percentage, and the fuel temperature within the same signal. The signal is both variable frequency and variable pulse width. The frequency signal indicates the ethanol percentage, and the pulse width indicates fuel temperature. The PCM provides an internal pull up to 5 volts on the signal circuit, and the FCS pulls the 5 volts to ground in pulses. The normal range of operating frequency is between 50-150 Hz. The normal pulse width ranges between 1-5 milliseconds. If the PCM detects a signal less than 45 Hz DTC P0178 will set.

2. P2269 Water in Fuel

DTC P2269 Water in Fuel

Circuit/System Description

A sensor/switch mounted in the bottom of the fuel filter housing is used to detect water in the fuel. The water in fuel (WIF) sensor/switch has an indicator control circuit and a low reference circuit. The engine control module (ECM) monitors the voltage to the WIF sensor/switch. If the voltage is incorrect, the ECM will illuminate the WIF lamp and set the appropriate DTC.

Diagnostic Aids

If DTC P2269 sets intermittently, fuel contamination may be the cause. Refer to Contaminants-in-Fuel Diagnosis. See: Component Tests and General Diagnostics\Contaminants-In-Fuel Diagnosis
On vehicle with a WIF float switch, a sticking float may illuminate the WIF lamp and set this DTC.

[LaszloT]

Despite the ERROR codes, this is not water in fuel. It is however a fuel issue with higher-than-standard ethanol content, and flushing the fuel system fixed it.

I'm not sure where the bad fuel came from, but the highest risk to fuel quality is handling at the gas station and the quality control procedures gas bar operators employ. Fly-by-night gas bars are not the best place for high quality fuel.