Jerking / Bucking Before Shift

bluescapegoat said:
Just like clearing the codes by unhooking the battery. Instead of waiting over night or something like that, I just disconnect the leads from the battery and touch them together to drain the system. I've been playing with the PCM in my Jeep a lot lately and that's quick and easy. Don't bridge the contacts on the battery itself.
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While I completely agree that the PCMs memory should be cleared after replacing sensors, with '05-'06 TJs, simply disconnecting the battery erases all long term memory and restores the PCM to factory settings. I had always been concerned about following the procedure you outlined until I found I'd been clearing the long term adaptive memory every time I disconnected the battery.

Next Generation Controller PCMs Page 86:

In an NGC PCM, Long Term Adaptive is maintained in memory by battery voltage; a battery disconnect will cause it to be erased.

Note: Whenever components that affect engine operation are replaced, the Adaptive Memory should be reset. If this is not done, when the engine is started and runs in Open Loop, it will use the Long Term Adaptive values stored while the component was malfunctioning. This could cause rough operation during warm-up after repairs.
 
bluescapegoat said:
Just like clearing the codes by unhooking the battery. Instead of waiting over night or something like that, I just disconnect the leads from the battery and touch them together to drain the system. I've been playing with the PCM in my Jeep a lot lately and that's quick and easy. Don't bridge the contacts on the battery itself.
Click to expand...
Thanks for the advice, it's helpful for down the road
 
AjRagno said:
Sorry I didn't include Mopar (OE) as sensors that will work. There are lots of reports of Bosch in particular not working in our TJs and that is what seems to be most readily available at parts stores.

P0401 is for the 02 sensor Heater Circuit. Clogged/Bad cats or exhaust leaks will not set this code. If it is not the sensor itself then it's either the wiring or the PCM. It's been my experience that if it's the PCM you would have codes for all of the 02 sensors so it's more likely an issue with the wiring harness between the 02 sensor connector and the PCM or between the 02 sensor connector and the sensor ground.

To test the wiring you'll need a multi-meter. You can also reference the service manual here: https://wranglertjforum.com/threads/jeep-wrangler-tj-factory-service-manuals-fsm-technical-documentation.4618/

Heater Circuit K299 18BR/WT
Ground Circuit Z43 18BK/LB

The service manual shows that the 1/2 and 2/2 sensors share a ground point of G105, which is that stud on the passenger side of the engine block, near the dipstick tube. The wires spice at S185, which looks to be that plastic loom housing behind the valve cover. Since the 2/2 sensor is working, if it's a ground issue with sensor 1/2, the issue is between this spice and the sensor connector.

If the ground circuit is good, disconnect and remove the battery and test for resistance between the sensor connector and the PCM's C3 connector, terminal 9.

When testing the wiring, it would also be helpful to have another person who can manipulate the harness to see if doing so changes the resistance.
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What section is that information under in the manual? I went to 2005 TJ service manual, emissions control and found where it talked about them but I couldn't find images or anything detailing what you mentioned. I can look for a stud and whatnot but an idea of where exactly to look would be helpful. That's an awesome resource either way, thank you.
 
AjRagno said:
While I completely agree that the PCMs memory should be cleared after replacing sensors, with '05-'06 TJs, simply disconnecting the battery erases all long term memory and restores the PCM to factory settings. I had always been concerned about following the procedure you outlined until I found I'd been clearing the long term adaptive memory every time I disconnected the battery.

Next Generation Controller PCMs Page 86:

In an NGC PCM, Long Term Adaptive is maintained in memory by battery voltage; a battery disconnect will cause it to be erased.

Note: Whenever components that affect engine operation are replaced, the Adaptive Memory should be reset. If this is not done, when the engine is started and runs in Open Loop, it will use the Long Term Adaptive values stored while the component was malfunctioning. This could cause rough operation during warm-up after repairs.
Click to expand...

Simply disconnecting and reconnecting does not immediately clear long term fuel trims, I know from repeated testing. Could just be some electricity stored in some capacitors, I don't know. Only takes a second to touch terminals the fuel trims are gone.
 
jordans05tj said:
What section is that information under in the manual? I went to 2005 TJ service manual, emissions control and found where it talked about them but I couldn't find images or anything detailing what you mentioned. I can look for a stud and whatnot but an idea of where exactly to look would be helpful. That's an awesome resource either way, thank you.
Click to expand...

The connector, splice and ground information is under Wiring.

02 Sensor Connector Pin Outs - Page 838
PCM C3 Connector Pin Outs - Page 843
2/2, 1/2 Splice and Ground Diagram - Page 662
Splice S185 and Ground G105 - Page 873
 
AjRagno said:
With your 05 TJ you do not need a scanner to read codes. Turn the ignition from OFF to ON 3 times without starting the engine. Any stored codes will be displayed in the odometer.
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I must be doing it wrong, or I don't have any codes. I turn my 05 LJ from OFF to ON three times, each time letting the odometer come up. On the third time, the odometer just stays there. Maybe I'm lucky and don't have any codes. I just figured there would be some random one stored in there.
 
AjRagno said:
The connector, splice and ground information is under Wiring.

02 Sensor Connector Pin Outs - Page 838
PCM C3 Connector Pin Outs - Page 843
2/2, 1/2 Splice and Ground Diagram - Page 662
Splice S185 and Ground G105 - Page 873
Click to expand...
Thank you so much, you've been very helpful
 
Dustoffdax said:
I must be doing it wrong, or I don't have any codes. I turn my 05 LJ from OFF to ON three times, each time letting the odometer come up. On the third time, the odometer just stays there. Maybe I'm lucky and don't have any codes. I just figured there would be some random one stored in there.
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It worked for me, you only go one click back once it's all the way forward
 
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Dustoffdax said:
I must be doing it wrong, or I don't have any codes. I turn my 05 LJ from OFF to ON three times, each time letting the odometer come up. On the third time, the odometer just stays there. Maybe I'm lucky and don't have any codes. I just figured there would be some random one stored in there.
Click to expand...

 
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AjRagno said:
The connector, splice and ground information is under Wiring.

02 Sensor Connector Pin Outs - Page 838
PCM C3 Connector Pin Outs - Page 843
2/2, 1/2 Splice and Ground Diagram - Page 662
Splice S185 and Ground G105 - Page 873
Click to expand...
So the ground by the dipstick is tight and there isn't any play in it, it appears to be connected well. I can't find any issues between the loom on the back of the valve cover and the sensor itself. I'm onto the next step where you said to disconnect the battery and test C3 terminal 9. I found which terminal it is in that manual, is this the C3 connector that I'm pointing to? I'll just be looking for resistance between one of the terminals on the sensor itself and the terminal on the PCM, correct?

PCM.jpg
 
jordans05tj said:
So the ground by the dipstick is tight and there isn't any play in it, it appears to be connected well. I can't find any issues between the loom on the back of the valve cover and the sensor itself. I'm onto the next step where you said to disconnect the battery and test C3 terminal 9. I found which terminal it is in that manual, is this the C3 connector that I'm pointing to? I'll just be looking for resistance between one of the terminals on the sensor itself and the terminal on the PCM, correct?

View attachment 132716
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Good to see that you have a multi-meter. I'm going to assume that you know how to use it to test for continuity. Yes, do disconnect the battery before unplugging the PCM connector. Not doing so can damage the PCM.

Rather that only a visual inspection, you should also use your multi-meter to test the ground wire from the 02 sensor connector to G105. Unplug the 02 sensor and check for continuity between cavity 2 and G105. If the ground wire tests good, move into testing the heater circuit wire from the 02 sensor connector to the PCM connector.

Yes, that is C3. When you unplug it, you should see that it's marked GREEN/NATURAL. You want to check for continuity between the 02 sensor connector cavity 1 and the PCM connector cavity 9.

During both of the above tests, it would be helpful to have an assistant who can manipulate the wiring harness to determine if the resistance change as the harness is moved. Often times you'll find that a wire is shorting out as the engine mounts flex.
 
AjRagno said:
Good to see that you have a multi-meter. I'm going to assume that you know how to use it to test for continuity. Yes, do disconnect the battery before unplugging the PCM connector. Not doing so can damage the PCM.

Rather that only a visual inspection, you should also use your multi-meter to test the ground wire from the 02 sensor connector to G105. Unplug the 02 sensor and check for continuity between cavity 2 and G105. If the ground wire tests good, move into testing the heater circuit wire from the 02 sensor connector to the PCM connector.

Yes, that is C3. When you unplug it, you should see that it's marked GREEN/NATURAL. You want to check for continuity between the 02 sensor connector cavity 1 and the PCM connector cavity 9.

During both of the above tests, it would be helpful to have an assistant who can manipulate the wiring harness to determine if the resistance change as the harness is moved. Often times you'll find that a wire is shorting out as the engine mounts flex.
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I'm an engineering student, multimeters are required 🤣

There is continuity from the ground on the O2 sensor plug to the G105 ground on the motor, I put my lead on the threaded part coming from the motor. I had my friend mess with the wires and nothing ever changed. I went from terminal 9 on the PCM plug to the O2 sensor and it was also continuous and didn't change as we moved the wires around. Doesn't appear to be a wiring issue from what I can tell. Maybe I got a bad sensor twice in a row? I'm out of ideas at this point. Any other causes for this light? I've had the battery off for an hour or so and I touched the positive/negative after I pulled the battery as someone else mentioned to be extra sure. I'll drive it and see if I get a light.
 
Light is back on, same P0141. I unplugged the sensor then turned the key on to measure voltage coming into the sensor. I got what appeared to be 0.622 volts. For reference I unplugged the 1/2 sensor and it got 0.629 according to my meter. These both seem low but the other functional sensor is getting a similar amount, so I'm just not sure what the problem is. I guess I've just gotten two bad sensors from both NTK and Mopar.
 
Diagnosing 02 Sensor Heater Circuit Failures

I think it's unlikely that the original sensor as well as the Mopar and NTK sensors would all set P0141. If the wiring checks out this brings the circuit in the PCM into question but I wouldn't want to condemn the PCM without being certain that's the issue.

This code will not cause any damage. At most, you would experience an increase in fuel consumption because the sensor is only being heated by the exhaust gasses. Maybe drive around for a few days and see if the MIL goes out.
 
AjRagno said:
Diagnosing 02 Sensor Heater Circuit Failures

I think it's unlikely that the original sensor as well as the Mopar and NTK sensors would all set P0141. If the wiring checks out this brings the circuit in the PCM into question but I wouldn't want to condemn the PCM without being certain that's the issue.

This code will not cause any damage. At most, you would experience an increase in fuel consumption because the sensor is only being heated by the exhaust gasses. Maybe drive around for a few days and see if the MIL goes out.
Click to expand...
I'll have the shop look into it when they have it and maybe I missed something, if not I'll just deal with the annoying light. Saves $500 or however much a PCM runs. Is that low of a voltage normal on that? Either way, you've been very helpful, thank you sir 👍
 
I was reading that article and he said it was on a 4.0 that recently had a valve cover gasket replaced and they pinched the wire. I also recently replaced my valve cover gasket so now I'm wondering if I did the same thing... That's an easy fix if so, if the shop can't find anything I'll look into that also. I did a warranty return on the Mopar sensor and the OE sensor is probably at the bottom of the landfill by now so I don't want to hack up my newest sensor to make the light, but if it gets bad enough I might do that. I can check the resistance on the new sensor to make sure it is all good.
 
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