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post #1 of 11 Old 09-24-2020, 01:44 PM Thread Starter
thechainrule
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4.0L Grounds

Looking for some help identifying the g104 and g103 grounds on my 2000 4.0L and where they should be attached on the chassis. Can someone help me with the following:

1. What ground # is this, where does it attach to the chassis?


2. What ground # is this, where does it attach to the chassis? I thought this one would be G104 and have a clear strap to the chassis but it looks like wires that vanish in a loom behind the engine block.



3. What ground # is this, where does it attach to the chassis?








NOTE: I went to the JY to do some research on a jeep already torn apart, this is not my Jeep!
I did try referencing the awesome grounds write up here https://www.jeepforum.com/forum/f310...94/index7.html


Last edited by thechainrule; 09-24-2020 at 08:11 PM. Reason: Annotated photos
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post #2 of 11 Old 09-24-2020, 02:48 PM
jtec
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you did not say - what year is this WJ? Pretty much the same BUT if I must get a manual at least I'll open the right one

Did you search for the WJ ground locations? uniblurb has a NICE sticky on this.
https://www.jeepforum.com/forum/f310...-info-4192594/

Also someone posted a link for the OEM WJ 2002 service manual - you should grab a PDF download ASAP - again just search...

If these do not help Let me know and I will check my work connections for the model year ypu tell me...

Chasing grounds has me wondering WHAT is the problem your working?

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #3 of 11 Old 09-24-2020, 03:36 PM Thread Starter
thechainrule
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Quote:
Originally Posted by jtec View Post
you did not say - what year is this WJ? Pretty much the same BUT if I must get a manual at least I'll open the right one

Did you search for the WJ ground locations? uniblurb has a NICE sticky on this.
https://www.jeepforum.com/forum/f310...-info-4192594/

Also someone posted a link for the OEM WJ 2002 service manual - you should grab a PDF download ASAP - again just search...

If these do not help Let me know and I will check my work connections for the model year ypu tell me...

Chasing grounds has me wondering WHAT is the problem your working?

Good call. This is for my 2000 4.0L

I am chasing an issue with all 4 of my 02 sensor heaters not working.
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post #4 of 11 Old 09-24-2020, 04:18 PM
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That might be codes- ?
P0135-1/1 O2 SENSOR HEATER FAILURE
P0141-1/2 O2 SENSOR HEATER FAILURE
P0155-2/1 O2 SENSOR HEATER FAILURE
P0161-2/2 O2 SENSOR HEATER FAILURE

PDC fuse #17 a 20amp, sends voltage to upstream and downstream O2 sensor HEATERS, relay control is junction box (JB) fuse # 21 a 10amp. sensors have a common ground G104.

Check the sensor heater resistance (4.0L O2 Heater element is 4.0 to 5.0 ohms) this is where most aftermarket sensors miss spec.
check ground integrity at the o2 sensor terminal 2.
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When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #5 of 11 Old 09-24-2020, 05:59 PM
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pic 1 should be your pcm ground strap. not really sure what you're pointing at, in 2 and three.

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post #6 of 11 Old 09-24-2020, 07:48 PM Thread Starter
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Quote:
Originally Posted by jtec View Post
That might be codes- ?
P0135-1/1 O2 SENSOR HEATER FAILURE
P0141-1/2 O2 SENSOR HEATER FAILURE
P0155-2/1 O2 SENSOR HEATER FAILURE
P0161-2/2 O2 SENSOR HEATER FAILURE

PDC fuse #17 a 20amp, sends voltage to upstream and downstream O2 sensor HEATERS, relay control is junction box (JB) fuse # 21 a 10amp. sensors have a common ground G104.

Check the sensor heater resistance (4.0L O2 Heater element is 4.0 to 5.0 ohms) this is where most aftermarket sensors miss spec.
check ground integrity at the o2 sensor terminal 2.


Yup, exactly! All 4 codes.

Found 1/2 of the equation. #17 on the PDC was blown! Still need to sort out the missing ground straps and get an multi-meter out to test the the resistance on the O2 sensors. When you measure the resistance are you measuring across the two black wires?
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post #7 of 11 Old 09-24-2020, 08:09 PM Thread Starter
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Quote:
Originally Posted by Golden-Arm View Post
pic 1 should be your pcm ground strap. not really sure what you're pointing at, in 2 and three.
This PCM ground strap is currently missing on my vehicle altogether. Its clear one end attaches to the block but where does the other end attach?

Here are some annotated images to clear up the rest.


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post #8 of 11 Old 09-24-2020, 08:38 PM
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it attaches to the upper mounting stud of the pcm. (2003 4.0 here, your year/engine size may vary) a clean mounting surface, and a serrated star type washer can help with the body grounds.

Uphill Slow, Downhill Fast, Tonnage First, Safety Last!
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post #9 of 11 Old 09-24-2020, 09:20 PM
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think top is G104 and trans filler mount and lower picture is ign capacitor ground/mount

Did fuse 17 correct o2 sensor issue?

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #10 of 11 Old 09-26-2020, 10:16 AM Thread Starter
thechainrule
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Thank you! Just got the faults cleared and replaced the #17 fuse. So far no CEL but it has only been 5 miles of driving or so. Is removing the battery ground for 30+ minutes the best way to reset the computer?

Still looking for how to ground the PCM though, I cant find the ground post by the PCM.
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post #11 of 11 Old 09-26-2020, 10:17 AM Thread Starter
thechainrule
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Quote:
Originally Posted by Golden-Arm View Post
it attaches to the upper mounting stud of the pcm. (2003 4.0 here, your year/engine size may vary) a clean mounting surface, and a serrated star type washer can help with the body grounds.
Would you happen to have a picture of the mounting stud you are referring to?
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