We have a 2012 Wrangler Ulimited Sahara and I got a P0128 code. Changed the thermostat out four days ago and drove from OKC to Fort Worth TX and did a little driving in Fort Worth. Got back to OKC last night. Didn’t notice any performance problems and the temp gauge was right in the middle the whole way just like usual. I hooked up my Launch 529 CReader OBD II to the Jeep late last night and still have the P0128 code. However, I also have a P0158 and P2098 code now. I have no idea what’s going on and any guidance would be greatly appreciated
Changed thermostat still have P0128
I fought a P0158 for years on my 2005. It's the heating element for an O2 sensor on the drivers side (in my 2005 at least).
P2098 looks to be a similar O2 sensor related issue.
Start by unplugging and replugging that O2 sensor clip (to make sure it's seated, and to inspect the connector), reset the codes and try again. Next would be to change out the O2 sensor (You'll want a good one, like Denso, not a cheap one).
The P0128 - Does your heater work normally, or does it only blow cold air?
You may want to make sure that there isn't air in the system. To burp it (at least the last way I did it), with the engine cold and off, you take off the radiator cap, start the engine, put heater on high, and top off the coolant. You'll be able to look in the radiator and see the coolant flow when the thermostat opens, at which time you may need to add more coolant.
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edit - Lunchbox, I accidentally deleted your post. That's why things disappeared for a bit. If you have any problems signing in, just email me at webmaster @ this site.
P2098 looks to be a similar O2 sensor related issue.
Start by unplugging and replugging that O2 sensor clip (to make sure it's seated, and to inspect the connector), reset the codes and try again. Next would be to change out the O2 sensor (You'll want a good one, like Denso, not a cheap one).
The P0128 - Does your heater work normally, or does it only blow cold air?
You may want to make sure that there isn't air in the system. To burp it (at least the last way I did it), with the engine cold and off, you take off the radiator cap, start the engine, put heater on high, and top off the coolant. You'll be able to look in the radiator and see the coolant flow when the thermostat opens, at which time you may need to add more coolant.
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edit - Lunchbox, I accidentally deleted your post. That's why things disappeared for a bit. If you have any problems signing in, just email me at webmaster @ this site.
The temp. gauge showed normal and the heater was blowing it’s normal hot air when we used it
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Would this O2 sensor be after the catalytic converter? If I understand what I’ve been reading I assume there are 4 total O2 sensors?
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I can only speak for my 05 TJ, on it there are 4 O2 sensors - one in front of each cat and one after each one. P0158 stands for O2 Sensor Circuit High Voltage (Bank 2, Sensor 2) - it was called "downstream" in some messages. I've also seen it listed as "2/2 O2 Sensor Shorted To Voltage", which could mean a cut or broken wire that has shorted out.
For me, it was the wiring on the rearmost O2 sensor, after the cat. I'd inspect yours for broken cables and the like, and if it looks good, get a new quality O2 sensor and swap it out. They aren't hard to do, as long as the engine isn't hot. There are really just 2 cables to each O2 sensor, and they screw in / out just like a sparkplug.
For me, it was the wiring on the rearmost O2 sensor, after the cat. I'd inspect yours for broken cables and the like, and if it looks good, get a new quality O2 sensor and swap it out. They aren't hard to do, as long as the engine isn't hot. There are really just 2 cables to each O2 sensor, and they screw in / out just like a sparkplug.
JPNinPA
Active member
P0128 coolant temp low.
As mentioned burp the system. When you replaced the thermo what temp brand and model did you use? Your vehicle calls to run at 210 and a 195 deg thermo will allow for the constant 210. If you run lower temp thermo the PCM tries to run leaner to raise the temp.
Based on the brand and type it is possible the thermo failed open almost immediately. What did the first one you took out look like? Look broken or stuck open?
Second is to check the temp sending unit. Some YJ models have 2. One for the gague and one for the PCM. All other models have one. You could check by measuring resistance across the terminals as the temp rises. It is possible it has a short at some temp. Ill post back the resistance readings per temp.
P2098: Post Catalyst – Fuel Trim System Too Lean – Bank 2
Could be relayed to the above.
Look for a exhaust leak just after the first O2 sensor but before the 2nd. It is possible if you ran lean too long the CAT material fell apart and the CAT is empty. This happened to me. The 2nd O2 looked crushed from the pieces banging into it. You could knock on the Cats and listen for rattling. Again mine were empty.
P0158 JEEP Code - O2 Sensor 2/2 Circuit High
The P0158 code is set when the Engine Control Module (ECM) detects that the rear O2 sensor signal voltage remains excessively high for an extended period of time.
Lean when the O2 voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The ECM interprets Rich when the HO2S voltage is above 0.45 V.
So P0158 and P2098 ate at odds one notes too much oxygen and the other is too little.
Also check your fuel level and run some injector cleaner. I had the 2098 when I ran out of fuel,
Never look down on anyone unless you are helping them up - Jesse Jackson
As mentioned burp the system. When you replaced the thermo what temp brand and model did you use? Your vehicle calls to run at 210 and a 195 deg thermo will allow for the constant 210. If you run lower temp thermo the PCM tries to run leaner to raise the temp.
Based on the brand and type it is possible the thermo failed open almost immediately. What did the first one you took out look like? Look broken or stuck open?
Second is to check the temp sending unit. Some YJ models have 2. One for the gague and one for the PCM. All other models have one. You could check by measuring resistance across the terminals as the temp rises. It is possible it has a short at some temp. Ill post back the resistance readings per temp.
P2098: Post Catalyst – Fuel Trim System Too Lean – Bank 2
Could be relayed to the above.
Look for a exhaust leak just after the first O2 sensor but before the 2nd. It is possible if you ran lean too long the CAT material fell apart and the CAT is empty. This happened to me. The 2nd O2 looked crushed from the pieces banging into it. You could knock on the Cats and listen for rattling. Again mine were empty.
P0158 JEEP Code - O2 Sensor 2/2 Circuit High
The P0158 code is set when the Engine Control Module (ECM) detects that the rear O2 sensor signal voltage remains excessively high for an extended period of time.
Lean when the O2 voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The ECM interprets Rich when the HO2S voltage is above 0.45 V.
So P0158 and P2098 ate at odds one notes too much oxygen and the other is too little.
Also check your fuel level and run some injector cleaner. I had the 2098 when I ran out of fuel,
Never look down on anyone unless you are helping them up - Jesse Jackson
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This is the therm I put in the Jeep;
Murray Plus 203 Degree Integrated Housing Thermostat
I didn’t really notice anything obviously wrong with the old therm, but I’m not very familiar with vehicles and vehicle parts.
I’ll look into checking the other things this coming weekend when we aren’t dealing with freezing rain and sleet. Hopefully I can get it figured out. Seemed strange to have all three of those codes pop up, yet the Jeep has been running fine.
Now that I think about it, just after changing the thermostat and heading to Texas I put in some premium gas instead of the regular I usually use. Wouldn’t think that would hurt anything. Thank you for the continued help. This could be a long project for me
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Murray Plus 203 Degree Integrated Housing Thermostat
I didn’t really notice anything obviously wrong with the old therm, but I’m not very familiar with vehicles and vehicle parts.
I’ll look into checking the other things this coming weekend when we aren’t dealing with freezing rain and sleet. Hopefully I can get it figured out. Seemed strange to have all three of those codes pop up, yet the Jeep has been running fine.
Now that I think about it, just after changing the thermostat and heading to Texas I put in some premium gas instead of the regular I usually use. Wouldn’t think that would hurt anything. Thank you for the continued help. This could be a long project for me
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JPNinPA
Active member
The gas shouldn’t matter especially reg to premium.
The thermo looks good and is the oem part. It has a bleeder valve in it and a leak through. That is good. Now id have to ask for the temp sender check. Start with just making sure the plug is in properly. Burp the system.
Did you do any exhaust work or head work that may cause a leak?
Leak doesn’t have to be big just enough in the correct spot
Never look down on anyone unless you are helping them up - Jesse Jackson
The thermo looks good and is the oem part. It has a bleeder valve in it and a leak through. That is good. Now id have to ask for the temp sender check. Start with just making sure the plug is in properly. Burp the system.
Did you do any exhaust work or head work that may cause a leak?
Leak doesn’t have to be big just enough in the correct spot
Never look down on anyone unless you are helping them up - Jesse Jackson
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JPNinPA
Active member
Not the best but has the basics of what and where.
2013 Jeep Wrangler Engine Coolant Temperature Sensor Replacement - YouTube
Never look down on anyone unless you are helping them up - Jesse Jackson
2013 Jeep Wrangler Engine Coolant Temperature Sensor Replacement - YouTube
Never look down on anyone unless you are helping them up - Jesse Jackson
I haven’t done any head or exhaust work and it sounds about the same. I’ll check the
Temp sensor this weekend and I’ll get the system burped
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Temp sensor this weekend and I’ll get the system burped
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JPNinPA
Active member
See if you could borrow a obdII reader you could pull temp data from and see what it is running at once at temp.
For reference my TJ is near temp within 1.5 miles of my house when thermo is good. Failed open it will take 5 mi to get to that temp.
Never look down on anyone unless you are helping them up - Jesse Jackson
For reference my TJ is near temp within 1.5 miles of my house when thermo is good. Failed open it will take 5 mi to get to that temp.
Never look down on anyone unless you are helping them up - Jesse Jackson
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