O2 Sensor Problem - Need HELP!!!

usmcgrunt · August 15th, 2009, 10:46 PM

I have a 99 GT with a few minor mods and its been running great for about 150,000 miles. The other day the cel comes on and it threw the codes for all four o2 sensors. They all say heater circuit malfunction (codes P0135/P0141/P0155/P0161). I'm having a hard time believing that all 4 sensors went bad at the exact same time. I don"t want to replace the sensors just to find out that the problem is somewhere else. Also, I'm in an emissions state (NC), so the o2 eliminators wont do me any good. Anyone have any ideas on what I should do from here? By the way, I haven't made any mods in a long time to the car and its been running strong until they other day. Its actually running stronger now, but my gas mileage has dropped drastically!!! Gotta love a rich running engine!! Thanks in advance for any help you can give me.

Stephen4036 · August 15th, 2009, 10:52 PM

you could get a DMM (Digital Multi Meter and test the resistance in your harness and in your plugs.

Does it have longtubes? If so those circuit codes can appear since the o2 sensor is further down on the header(manifold).

If you have a tuner (Diablo/SCT/Etc) your tuner should be able to clear those codes out since my buddy had them after v6 Long Tube install and Justin @ VMP Cleared some of them.

usmcgrunt · August 15th, 2009, 11:00 PM

I forgot one of the most important things when dealing with this... my exhaust is factory from the motor to the cats. I'm wondering if there is some sort of relay other electrical crap that could cause all four heaters to go out at the same time. I love my current Pony, but I miss my old '65 289 4v!!!

ccaberle · September 21st, 2009, 10:45 AM

Check your fuses. I believe it is F2.8 20 amp. I had the same problem.

Trick Tuners · September 21st, 2009, 03:03 PM

Yup, check the fuses and make sure none of the o2 wires shorted out on the headers.

August 15th, 2009, 10:46 PM	#1
usmcgrunt Newbie 1999 Mustang GT Join Date: Aug 2009 Location: Camp Lejeune, NC Posts: 11 iTrader: 0 reviews	O2 Sensor Problem - Need HELP!!! I have a 99 GT with a few minor mods and its been running great for about 150,000 miles. The other day the cel comes on and it threw the codes for all four o2 sensors. They all say heater circuit malfunction (codes P0135/P0141/P0155/P0161). I'm having a hard time believing that all 4 sensors went bad at the exact same time. I don"t want to replace the sensors just to find out that the problem is somewhere else. Also, I'm in an emissions state (NC), so the o2 eliminators wont do me any good. Anyone have any ideas on what I should do from here? By the way, I haven't made any mods in a long time to the car and its been running strong until they other day. Its actually running stronger now, but my gas mileage has dropped drastically!!! Gotta love a rich running engine!! Thanks in advance for any help you can give me.

August 15th, 2009, 10:52 PM	#2
Stephen4036 Banned 2000 Mustang GT 14.10 @ 98 Join Date: Aug 2009 Location: Orlando, FL Posts: 491 iTrader: 0 reviews	you could get a DMM (Digital Multi Meter and test the resistance in your harness and in your plugs. Does it have longtubes? If so those circuit codes can appear since the o2 sensor is further down on the header(manifold). If you have a tuner (Diablo/SCT/Etc) your tuner should be able to clear those codes out since my buddy had them after v6 Long Tube install and Justin @ VMP Cleared some of them. __________________ [SIGPIC][/SIGPIC] [LEFT][B][COLOR="Red"]4r70w to TR3650 Swap...[/COLOR] [COLOR="Red"][COLOR="Yellow"]SRA to 2001 IRS Swap...[/COLOR][/COLOR] [COLOR="Orange"]2000 2v to 98 4v Swap...[/B][/COLOR] [COLOR="RoyalBlue"][B][I]there really isn't much else to swap... :cool:[/I][/B][/COLOR][/LEFT]

September 21st, 2009, 03:03 PM	#5
Trick Tuners MM Fanatic KB'd GT Join Date: Nov 2006 Location: San Diego Posts: 4,471 iTrader: 3 reviews	Yup, check the fuses and make sure none of the o2 wires shorted out on the headers. __________________ Check out my forums for stuff on troubleshooting, tuning, etc We teamed up with Socal Performance Racing to bring dyno tuning to San Diego. Be friends with us on FB

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August 15th, 2009, 11:00 PM	#3
usmcgrunt Newbie 1999 Mustang GT Join Date: Aug 2009 Location: Camp Lejeune, NC Posts: 11 iTrader: 0 reviews	I forgot one of the most important things when dealing with this... my exhaust is factory from the motor to the cats. I'm wondering if there is some sort of relay other electrical crap that could cause all four heaters to go out at the same time. I love my current Pony, but I miss my old '65 289 4v!!!

September 21st, 2009, 10:45 AM	#4
ccaberle Look Ma! My First Post! Join Date: Sep 2009 Posts: 1 iTrader: 0 reviews	Check your fuses. I believe it is F2.8 20 amp. I had the same problem.

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