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post #1 of 4 (permalink) Old 06-18-13, 04:31 AM Thread Starter
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Open Loop Fuel Fault

Hi, I have an mk4 ford fiesta 1.25 zetec and have had it plugged into my OBD scanner and it says i have an Open loop fuel fault and that its not going into the closed loop so the fuel mixture is rich and so its burning more fuel. Im getting no trouble codes up just on the fuel system says I have that fault and that the oxygen sensor and oxygen sensor heater is not working! but again no proper codes.

I have replaced the front oxygen/lambda sensor naturally as thats what it is all pointing to, but still no luck. Any ideas what else it could be? maybe a wiring fault somewhere? Anyone had a similar problem? Thanks

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post #2 of 4 (permalink) Old 06-18-13, 05:03 AM
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Re: Open Loop Fuel Fault

This might help you

http://www.motorcraftservice.com/vdi...DSM1300_16.pdf

Page 112 refers to the open loop .
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post #3 of 4 (permalink) Old 06-23-13, 08:55 AM Thread Starter
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Re: Open Loop Fuel Fault

Thanks will have a look :) Im gonna try and measure the volts on the sensor with a voltmeter, as far as i know they should create a bit of voltage on there own without the sensor plugged in? Its showing no voltage at all on though through the OBD scanner :/
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post #4 of 4 (permalink) Old 06-23-13, 11:26 AM Thread Starter
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Re: Open Loop Fuel Fault

Had it plugged into the OBD when the sensor and engine were completely cold and as I started the car with the scanner in could watch the voltage rise how it should do, past the normal open loop point at 0.45 and changed into closed loop like normal and up to about 0.60 where it would usually start falling again and do the normal up and down loop, but as it gets to 0.60 the voltage suddenly drop down to 0.00 and wont rise again! Will only do that when its completely cold, Any ideas what that is? will try post the graph from the scanner
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