o2 Htr Problems

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Jan 16, 2006 | 10:52 AM

Sellout9182

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o2 Htr Problems

Hi, I am new to these forums and I have a 1996 F150 4x4. My engine light came on so I pulled the codes and all three o2 Htr's came up. Right now I am trying to find a wiring diagram for my computer/main harness, it is a 72 pin harness all I can find is the wiring diagram for the 102 and 36 pin harness. I tested the htr and one was bad so I replaced that one. Engine light stayed off for a bit, but came back on saying the one I just replaced was the problem. So I cleared it again and all three popped up this time. I am guessing it is not o2 sensors since I tested the htrs and they checked out. So I am wondering if this is a known issue or if anyone can find me the right wiring diagram. I am stumped so any help would be great.

Jan 16, 2006 | 11:23 AM

jroehl

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From: Lafayette, IN

If you're getting codes on all your Heated Exhaust Gas Oxygen sensors, they're probably not the problem. The codes you're getting are probably a "too lean"; "too rich"; or some other "out of range" code. That doesn't necessarily mean that the HEGO sensors are bad (they could be), but it likely means that your engine is not running properly and the HEGO sensors are actually doing their job. Too many people run out and blow $50 on a HEGO sensor as soon as they get the code, when in reality it's just that their engine isn't running correctly.

Jason

Jan 16, 2006 | 01:06 PM

Sellout9182

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The o2 sensors are reading right, it is saying heater circuit problems. So I was looking to get a wiring diagram for the 76 pin connector on the computer. B/c all three htr circuits will read bad and then the next time only the one that we replaced. Keep in mind the is just the heater not the o2 it self, the heater just warms the sensor up so it can read quicker. So the sensor is working right, but the heater inside to get it up to temp faster isn't. There was a bit of moisture in the 76 pin connecter, I used contact cleaner and blew it out. So the main thing I am looking for is a wiriing diagram for the computer/harness.

Jan 16, 2006 | 04:45 PM

Sellout9182

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Bump... No one knows where to find a diagram for the 76 pin connector on the computer?

Jan 16, 2006 | 06:58 PM

Popa Tim

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From: Central NY

Subford may have a pinout/schematic for this year. The 96 was odbii and a bit different than the earlier years in that respect. Not too many of the forum users have a 96...

Also I just wanted to point out, that if you search, you will come across a few other 96's with the same problem, that turned out to be the pcm. You're on the right track imo, but if you have access to another pcm it may be quicker to swap than wait for the schematic.

Good luck and let us know the culprit.
Thanks,
Tim

Jan 16, 2006 | 07:48 PM

EPNCSU2006

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From: Concord, NC

I want to say there is a fuse for the heater circuits, so maybe have a look in the power distribution box and see if there is anything obviously blown. Next thing to do is test for 12V (and ground) at the O2 sensor connectors with the key on, engine off.

Jan 17, 2006 | 09:05 AM

Sellout9182

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K thanks I kind of thought it might have been a known problem on these trucks. I will try to find another pcm. And yes I did test for 12 volts and groud and test the resistents on the heaters. So I know that they are good sensors that is why I suspected the PCM.