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P0031 after replacing all 4 O2 sensors, EGR, plugs/wires/coil

 
Old 05-13-2019, 02:20 PM
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Default P0031 after replacing all 4 O2 sensors, EGR, plugs/wires/coil

Hey guys, first post. Sorry to ask for help before contributing anything, but Iím kind of lost. I replaced all four O2 sensors, EGR valve, plugs/wires/coil today on my wifeís 08 Unlimited Sahara to battle a plethora of codes, including multiple 02 sensor faults and a random misfire issue. Jeep runs amazingly well now, but I still have a P0031 code. Iíve looked pretty hard on google, YouTube, etc, but cannot find anything JK specific regarding a fix or troubleshooting procedure. Iíd really appreciate any help yíall can give, Iím really struggling here. Iím back at it tomorrow doing ball joints and some other maintenance items so Iíll be able to run down any rabbit holes yíall can suggest. Thanks!

doug
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Old 05-13-2019, 02:54 PM
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1/1 o2 sensor heater control circuit... Make sure you have no power to o2 sensor heater circuit with key off, if you do you will burn out o2 sensor. Basically you have a wiring issue from pcm to 1/1 o2 sensor (circuit k99 br/lg wire cavity 1) or you have a bad ground from o2 to ground (z906 black wire cavity 2).. Check for power with command heater on to k99, check ground at cavity 2... If this checks out you have a defect o2
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Old 05-18-2019, 05:26 PM
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Default Is it possible

Hi
I had all of these codes show up at on time:
P0031 P0037 P0051 P0057

Could all four actually go out at the same time? I have a 2008 JK Sahara

Thanks George
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Old 05-18-2019, 06:31 PM
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Originally Posted by gfe jeep View Post
Hi
I had all of these codes show up at on time:
P0031 P0037 P0051 P0057

Could all four actually go out at the same time? I have a 2008 JK Sahara

Thanks George
Hi George, all those are O2 heater circuit low codes -- Strange, even more significant is that replacing all four O2 sensors cleared all but one. Here's the potential causes from the manual, the difference between codes is which O2 sensor. P0031 is 1/1 (passenger upstream).

Possible Causes
O2 SENSOR XY HEATER CONTROL CIRCUIT SHORTED TO GROUND
O2 SENSOR
PCM
It looks like a current limited circuit in the sense that a ground will sink the voltage to near zero and set the circuit low code. Conversely, if the heater is an open circuit the voltage goes high and sets the circuit high code. The 70F O2 heater resistance is supposed to be 2 to 30 ohms, the heater + is pin 1, the - (ground) is pin 2 of the connector.

Last edited by Mr.T; 05-18-2019 at 06:41 PM.
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Old 05-19-2019, 05:50 AM
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Default Thanks Mr T

Thanks for the information. This was my original issue then other codes and problems were found. I eliminated all except these four. I also read about 02 eliminators but would do that as a last resort. I think some of my problems were a caused by a spike in voltage from the alternator. I have determined the PCM is working, repaired some grounds (one was broken that went to the engine block). During this time I replaced the ERG, and spark plugs and wires. I have a Crankshaft Position sensor on order for rough idle. I'll check the wires that go into the )2 sensor plugs next.

I'll see if I can find hows this is operating!
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