O2 sensor heater circuit
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From: Pendleton Oregon
O2 sensor heater circuit
Sorry if this topic has been beaten to death. I have done a search related to my problem and am not getting any real direction that I can seem to understand. My problem is I keep getting codes from a oxygen sensor heater circuit, bank 2 sensor 1. It has a 5.8l enging. I have replaced all 3 sensors with new bosch sensors, and have put in a new mass airflow sensor. I keep getting this code. Where do I go now. Any help is very much appreciated.
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From: Wetaskiwin, Alberta
Are you getting any other codes? The reason that I ask is usually the O2 sensor is at the end of the line for a lot of related faults. In other words, other things can crap out or go out of adjustment that will trigger the O2 sensor codes. Unless you fix what actually CAUSES the O2 sensor to code you will never resolve the problem. Can you give us a little more info. about the truck like mileage, any recent mods, any other symptoms like poor idle etc. etc.? If you have MAF then your truck is of the 96 or newer style which is an OBD11 system and definitely beyond my meagre knowledge base. You could also try a search in this forum under a string like "Os Sensor problems" or something like that. You will come up with a whack of hits that should point you in the right direction. Stick around and others will chime in with some help.
Cheers!
Mike
Cheers!
Mike
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From: Topsfield, MA
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From: Pendleton Oregon
Its a 1996 f150, 5.8L with 92,000 miles. My brother works at a local shop. I took it to him and he pulled the codes and all three 02 sensor heater circuit codes showed. I replaced all three took it back to him. he cleared the codes. I drove away and about 10 miles down the road the light came back on. Took it back, this time same code bank 2 sensor 1. At this point I have replaced all 3 o2 sensors and the MAF. I have visually looked over all the pigtails on the sensors and don't see any wiring issues, at least that are obvious.
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From: Pendleton Oregon
I forgot to post, the truck seems to run just fine. It has no drivability issued. Just that dang light!
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From: Pendleton Oregon
I don't know. What I've been told to this point is on O2 heater circuit codes. I think one of the previous codes showed lean on bank 2 sensor 1. But this sensor is before the cat???
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From: Oak Harbor, OH
Is it possible that you're pulling the codes with the engine cold? If it's not fully warmed up the computer will throw a bunch of bogus temperature related codes. Take the truck on a good long drive get it fully warmed up. Come back and check the codes. If it's still throwing O2 sensor codes find out what they are. It will call all O2 sensor problems HEGO or heated exhaust gas oxygen sensor codes. It may be indicating a rich or a lean condition which will tell you where to look for other problems.
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From: Pendleton Oregon
I took it to a local shop today to have the wiring to all the o2 sensors checked and anthing else that may be tripping the codes. Nothing abnormal found. It will be making a trip to the Ford dealership on Thursday. Search results indicate this problem has existed with others and the solution seems to the be the ecu on occasion.
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From: Concord, NC
Could be the ECU, but that would be the last thing I would suspect. What I would do is get a voltmeter and test the heater wires for 12V and a solid connection to ground with the key on, engine off. This will tell you if in fact it is a problem with the sensor or the wiring. I would also check the O2 sensor heater fuse and relay for proper operation. This code shouldn't have anything to do with the mixture. It is simply the 12V heater in the O2 sensor or its related wiring that is not registering in the computer.
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From: Pendleton Oregon
The trucks spent all day yesterday at my brothers shop, where he looked for anything outside the norm. Checked the pigtails for power, took ohm meter to all the wires looking for broken connections or shorts, checked fuses and relays for any sign of anything wrong, swapped with other 02 sensors. Nothing found. I have also done a search on the 02 sensor heater circuit and have found on a number of occasions it was the ECU. It's making a trip tomorrow to the Ford dealership. I just have a feeling this is going to be it, but hope I'm wrong and it's something more simple.
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From: York, PA
On this engine performance wiring, the oxygen sensors are ground controlled by the ECM at pins 93, 94 and 95. Measure voltage with key on engine off at the oxygen sensors RED wire (all three), need 12v power. If that is ok, go to the ECM and start the vehicle, if your brother has access to a labscope or a graphing meter and you might be able to squeak by with a digital meter, look at pins 93 (red/wht), 94(yel/lt blu) and 95(wht/blk). These three wires need to be dropped from "12" volts to "0" volts if the ECM is working correctly. If your brother has access to a scan tool, the oxygen sensors need to hit 900 millivolts within 30 seconds after startup for them to be good, or the circuit to be good. Also look at the ground connection at the right fender apron, right side of the battery, there is a set of blk/wht wires that are bolted down at that location, all of these are the ECM power grounds.
Hope this helps, broken wire
Hope this helps, broken wire
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From: Pendleton Oregon
Well, I got word back from the Ford dealership today. They say it is the ECU that needs replaced. Thanks everyone for you input. I'll make a final post once I actually get the truck back and it's confirmed fixed. thanks again.