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  #1  
Old May 12th, 2019, 01:52
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4x4JeePmaNthINg 4x4JeePmaNthINg is offline
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99 engine grounds

Having some trouble deciphering grounds from rear passenger side of block. I have the wiring diagrams, but can anyone clarify where these wires go.
The fsm muddys down here.


The rear ground and coil block grounds have two wires per ring. I can trace what connects to the Pcm only, these splice somewhere.

I'm trying to make sure I'm getting good test results with a meter for wires being grounded and not broken or corroded. These cut off somewhere in not testing because I'm not finding there termination points.

Any one that's dissected the 99 harness might know well, but I'm all ears.


Cheers.
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Old May 12th, 2019, 07:01
RCP Phx RCP Phx is offline
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Re: 99 engine grounds

A lot of them are spliced "within" the harness, like the the coil(s) and the injectors.
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Old May 12th, 2019, 07:47
RCP Phx RCP Phx is offline
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Re: 99 engine grounds

Here's a 2000 harness that I had to re-work.

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Originally Posted by RCP Phx View Post
In the mean time the harness has been a major P.I.T.A., all 3 harnesses have some damage from the area around #5-6. It is done now except I need more split-loom!





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Old May 12th, 2019, 11:37
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Re: 99 engine grounds

I wonder if Painless Wiring has given any thought to the XJs.

I see they have a harness for the '87-'91 YJ.

I imagine the time is coming when there will be justifiable demand for XJ harnesses. I expect transition years like my '96 won't make the cut though.
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Old May 12th, 2019, 12:01
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Re: 99 engine grounds

Iirc one is to the oxy sensor heater
One is the driver earth from the pcm/ injector / coil
One is pcm earth & sensor earth.
There may be more.
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Old May 12th, 2019, 12:53
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Re: 99 engine grounds

What is earth, I'm new to this?
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Old May 12th, 2019, 13:09
RCP Phx RCP Phx is offline
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Re: 99 engine grounds

Ground.....
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Old May 12th, 2019, 13:12
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Re: 99 engine grounds

More importantly I shoukd ask where can I get another reading for continuity on these wires. I've gotten sensors to pcm. Best I can figure anything tied to these splices seems to be working.

I need to know definitively that all wiring grounds are good,hard to do not knowing where termination points are, everything bolted down is tight and clean like new.
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Old May 12th, 2019, 13:26
RCP Phx RCP Phx is offline
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Re: 99 engine grounds

For sensors I would do a "point to point" continuity test from the sensor connection to both a "body" ground and the PCM harness.
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Old May 12th, 2019, 13:30
RCP Phx RCP Phx is offline
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Re: 99 engine grounds

I wasn't thinking right about the injectors. They have a common "B+" feed with individual grounds the are "switched" by the PCM.
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Old May 12th, 2019, 14:34
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Re: 99 engine grounds

So I've tested continuity on sensors, and from ckp, cmp to pcm. These are good, but they share a ring with other stuff which is why need to know everything is gtg.

Where you went through the harness, are these splice points soldered?

What would happen if i added/ spliced new grounds from sensors outs and attached them to the block, would this interior and grounding if a main harness wire was corroded or frayed?
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Old May 13th, 2019, 11:59
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Re: 99 engine grounds

mate I i Wouldn’t be going for D I Y grounds in the sensor circuit.
You could end up with voltage differences between the sensors and the pcm reference voltage. In a vehicle that is known to be sensitive to ground issues, that could well cause more problems than it fixes.


What exactly is the problem?
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Old May 13th, 2019, 12:31
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Re: 99 engine grounds

Crap, yeah i Kinda figured as much. The problem is an intermittent signal loss code.
Cmp/ckp Grounds have been tested at pcm.
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Old May 18th, 2019, 15:55
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Re: 99 engine grounds

Quote:
Originally Posted by RCP Phx View Post
For sensors I would do a "point to point" continuity test from the sensor connection to both a "body" ground and the PCM harness.
While running or key on?

Last time I back probed the sensors and grounded to battery negative.

If a ground doesn't read on a ring terminal is this potentially because of the splice in the harness?
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