Kirk Miller

Well I finally crawled under the car with my DVM. I noticed I had about 3.5
ohms of resistance to ground for the signal wire on the oxygen sensor. I
looked at the electrical schematic in Haynes and it looks like all the
grounds are spliced at "K4" then grounded to chassis. I couldn't find any
chassis grounds besides the one coming off the negative battery cable. Is
there another location for the ground? What does a "K4" splice look like and
what is it near?

I spliced a wire on the MAP sensor ground and tied the wire to the intake
manifold. My erratic idle has disappeared and check engine light hasn't
come on yet after 16 miles of driving. I think I might have found the
problem. I would like to fix the root problem though. Prior to adding the
ground, the check engine light would come on every time I drove the car.

Thanks,
Kirk

This is what I posted a few weeks ago with no response:

My '94 Jeep Grand Cherokee has been acting up. The check engine light comes
on and goes off irregularly. When I check the flashing light I get 12 and 21
as the codes. The vehicle is pre-OBDII.

I hadn't disconnected the battery at any point, so I don't know why
disconnected battery code would record. I replaced the O2 sensor and it
didn't seem to affect the check engine light being on or off. So I doubt it
was the O2 sensor causing the problem.

When the check engine light is on, the idle tends to be rough and below 500
rpm. Upon start up, if the engine revs to 2000 RPM by itself, then comes
down to an irregular idle, the check engine light will come on shortly
thereafter.

I do notice some other erratic things like the oil pressure gauge
fluctuating greatly and the voltage meter on the dash is consistently below
14 V when the check engine light is on.

At no time does the vehicle suffer from low power or the ability to drive at
highway speeds.

I cleaned the battery terminals, checked the electrolyte levels. The
voltage across the battery terminals at idle or revved up doesn't get above
13.8 V using my digital voltmeter, Haynes says the voltage should be between
14 and 15 V. When the engine isn't running the battery measures about 12.8
V. So I presume the battery is good.

The battery hasn't ever discharged noticeably.

From the Haynes discription the Voltage is controlled by the PCM which is
separate from the alternator. Does anybody have a similar experience and
successful repair strategy? I am trying to avoid playing the musical parts
replacement tune again.

This '94 GJC 4.0 liter has 138000 miles on it.

Thanks in Advance,
Kirk

Kirk Miller

Every sensor I checked, map, tps, & o2 had resistances of about 2.5 to 3.5
ohms from the ground pin to chassis. There is only .1 ohm resistance between
the negative terminal and the chassis ground on the fender well and the
negative terminal. Does the wire loom ground at the fender near the battery?

I will check the resistance between the negative terminal and the engine.
The connection at the block doesn't look corroded. First I will have to
disconnect the ground I added. Have to save it for after work.....

Thanks,
Kirk

"DougW" <post.replies@invalid.address> wrote in message
news:puw7b.2510$8o3.918@news2.central.***.net...
> Kirk Miller wrote:
> > Well I finally crawled under the car with my DVM. I noticed I had about
3.5
> > ohms of resistance to ground for the signal wire on the oxygen sensor.
I
> > looked at the electrical schematic in Haynes and it looks like all the
> > grounds are spliced at "K4" then grounded to chassis. I couldn't find
any
> > chassis grounds besides the one coming off the negative battery cable.
Is
> > there another location for the ground? What does a "K4" splice look like
and
> > what is it near?
> >
> > I spliced a wire on the MAP sensor ground and tied the wire to the
intake
> > manifold. My erratic idle has disappeared and check engine light hasn't
> > come on yet after 16 miles of driving. I think I might have found the
> > problem. I would like to fix the root problem though. Prior to adding
the
> > ground, the check engine light would come on every time I drove the car.
>
> 12 will happen if your battery is ever drained or disconnected or if
> the battery terminals are loose or corroded. It only resets after
> fifty, yes 50, starts.
>
> K4 isn't a description, just a numbering convention.
> It's located in the loom, passenger side of the engine
> block by the firewall. Outboard from where the oil pressure
> wires enter the loom.
>
> I would suspect a corroded pin in the O2 sensor connector
> before a break in the harness. Then again, check the resistance
> between the engine block and battery -. The I6 has a ground strap
> and if that is corroded all sorts of funky things come to play.
>
> --
> -- DougW -- 93 ZJ 4.0 http://members.***.net/wilsond
> HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
> Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
>
>
>

Kirk Miller

Every sensor I checked, map, tps, & o2 had resistances of about 2.5 to 3.5
ohms from the ground pin to chassis. There is only .1 ohm resistance between
the negative terminal and the chassis ground on the fender well and the
negative terminal. Does the wire loom ground at the fender near the battery?

I will check the resistance between the negative terminal and the engine.
The connection at the block doesn't look corroded. First I will have to
disconnect the ground I added. Have to save it for after work.....

Thanks,
Kirk

"DougW" <post.replies@invalid.address> wrote in message
news:puw7b.2510$8o3.918@news2.central.***.net...
> Kirk Miller wrote:
> > Well I finally crawled under the car with my DVM. I noticed I had about
3.5
> > ohms of resistance to ground for the signal wire on the oxygen sensor.
I
> > looked at the electrical schematic in Haynes and it looks like all the
> > grounds are spliced at "K4" then grounded to chassis. I couldn't find
any
> > chassis grounds besides the one coming off the negative battery cable.
Is
> > there another location for the ground? What does a "K4" splice look like
and
> > what is it near?
> >
> > I spliced a wire on the MAP sensor ground and tied the wire to the
intake
> > manifold. My erratic idle has disappeared and check engine light hasn't
> > come on yet after 16 miles of driving. I think I might have found the
> > problem. I would like to fix the root problem though. Prior to adding
the
> > ground, the check engine light would come on every time I drove the car.
>
> 12 will happen if your battery is ever drained or disconnected or if
> the battery terminals are loose or corroded. It only resets after
> fifty, yes 50, starts.
>
> K4 isn't a description, just a numbering convention.
> It's located in the loom, passenger side of the engine
> block by the firewall. Outboard from where the oil pressure
> wires enter the loom.
>
> I would suspect a corroded pin in the O2 sensor connector
> before a break in the harness. Then again, check the resistance
> between the engine block and battery -. The I6 has a ground strap
> and if that is corroded all sorts of funky things come to play.
>
> --
> -- DougW -- 93 ZJ 4.0 http://members.***.net/wilsond
> HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
> Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
>
>
>

Kirk Miller

The resistance from negative terminal to engine is also 0.1 ohm. That means
the resistance caused by some connection between the "K4" splice and the
ground connection.

Does anyone know where the chassis ground connection is physically located
in the engine compartment for the "K4" splice?

Thanks,
Kirk
"Kirk Miller" <krik.rellim@comcast.net> wrote in message
news:eCD7b.405661$YN5.273436@sccrnsc01...
> Every sensor I checked, map, tps, & o2 had resistances of about 2.5 to 3.5
> ohms from the ground pin to chassis. There is only .1 ohm resistance
between
> the negative terminal and the chassis ground on the fender well and the
> negative terminal. Does the wire loom ground at the fender near the
battery?
>
> I will check the resistance between the negative terminal and the engine.
> The connection at the block doesn't look corroded. First I will have to
> disconnect the ground I added. Have to save it for after work.....
>
> Thanks,
> Kirk
>
> "DougW" <post.replies@invalid.address> wrote in message
> news:puw7b.2510$8o3.918@news2.central.***.net...
> > Kirk Miller wrote:
> > > Well I finally crawled under the car with my DVM. I noticed I had
about
> 3.5
> > > ohms of resistance to ground for the signal wire on the oxygen sensor.
> I
> > > looked at the electrical schematic in Haynes and it looks like all the
> > > grounds are spliced at "K4" then grounded to chassis. I couldn't find
> any
> > > chassis grounds besides the one coming off the negative battery cable.
> Is
> > > there another location for the ground? What does a "K4" splice look
like
> and
> > > what is it near?
> > >
> > > I spliced a wire on the MAP sensor ground and tied the wire to the
> intake
> > > manifold. My erratic idle has disappeared and check engine light
hasn't
> > > come on yet after 16 miles of driving. I think I might have found the
> > > problem. I would like to fix the root problem though. Prior to adding
> the
> > > ground, the check engine light would come on every time I drove the
car.
> >
> > 12 will happen if your battery is ever drained or disconnected or if
> > the battery terminals are loose or corroded. It only resets after
> > fifty, yes 50, starts.
> >
> > K4 isn't a description, just a numbering convention.
> > It's located in the loom, passenger side of the engine
> > block by the firewall. Outboard from where the oil pressure
> > wires enter the loom.
> >
> > I would suspect a corroded pin in the O2 sensor connector
> > before a break in the harness. Then again, check the resistance
> > between the engine block and battery -. The I6 has a ground strap
> > and if that is corroded all sorts of funky things come to play.
> >
> > --
> > -- DougW -- 93 ZJ 4.0 http://members.***.net/wilsond
> > HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
> > Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
> >
> >
> >
>
>

Kirk Miller

The resistance from negative terminal to engine is also 0.1 ohm. That means
the resistance caused by some connection between the "K4" splice and the
ground connection.

Does anyone know where the chassis ground connection is physically located
in the engine compartment for the "K4" splice?

Thanks,
Kirk
"Kirk Miller" <krik.rellim@comcast.net> wrote in message
news:eCD7b.405661$YN5.273436@sccrnsc01...
> Every sensor I checked, map, tps, & o2 had resistances of about 2.5 to 3.5
> ohms from the ground pin to chassis. There is only .1 ohm resistance
between
> the negative terminal and the chassis ground on the fender well and the
> negative terminal. Does the wire loom ground at the fender near the
battery?
>
> I will check the resistance between the negative terminal and the engine.
> The connection at the block doesn't look corroded. First I will have to
> disconnect the ground I added. Have to save it for after work.....
>
> Thanks,
> Kirk
>
> "DougW" <post.replies@invalid.address> wrote in message
> news:puw7b.2510$8o3.918@news2.central.***.net...
> > Kirk Miller wrote:
> > > Well I finally crawled under the car with my DVM. I noticed I had
about
> 3.5
> > > ohms of resistance to ground for the signal wire on the oxygen sensor.
> I
> > > looked at the electrical schematic in Haynes and it looks like all the
> > > grounds are spliced at "K4" then grounded to chassis. I couldn't find
> any
> > > chassis grounds besides the one coming off the negative battery cable.
> Is
> > > there another location for the ground? What does a "K4" splice look
like
> and
> > > what is it near?
> > >
> > > I spliced a wire on the MAP sensor ground and tied the wire to the
> intake
> > > manifold. My erratic idle has disappeared and check engine light
hasn't
> > > come on yet after 16 miles of driving. I think I might have found the
> > > problem. I would like to fix the root problem though. Prior to adding
> the
> > > ground, the check engine light would come on every time I drove the
car.
> >
> > 12 will happen if your battery is ever drained or disconnected or if
> > the battery terminals are loose or corroded. It only resets after
> > fifty, yes 50, starts.
> >
> > K4 isn't a description, just a numbering convention.
> > It's located in the loom, passenger side of the engine
> > block by the firewall. Outboard from where the oil pressure
> > wires enter the loom.
> >
> > I would suspect a corroded pin in the O2 sensor connector
> > before a break in the harness. Then again, check the resistance
> > between the engine block and battery -. The I6 has a ground strap
> > and if that is corroded all sorts of funky things come to play.
> >
> > --
> > -- DougW -- 93 ZJ 4.0 http://members.***.net/wilsond
> > HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
> > Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
> >
> >
> >
>
>

Mike Romain

I don't know the Grand, but can offer some ideas.

I believe the harness sensor grounds are tagged to the computer, could
be wrong, but there are a bunch of small black wires bolted to most
engine blocks somewhere near the oil sender that are for the 'computer'
signal/sensor grounds.

There also is one on the Cherokee up under the dash above the gas pedal
on the firewall. The YJ has one on the e-brake pedal housing too.

Most engines are also grounded to the firewall with a mesh cable. This
sucker likes to rot away and/or get corroded ends. It usually comes off
the top back of the head or off the bell housing and goes to the
firewall.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

Kirk Miller wrote:
>
> The resistance from negative terminal to engine is also 0.1 ohm. That means
> the resistance caused by some connection between the "K4" splice and the
> ground connection.
>
> Does anyone know where the chassis ground connection is physically located
> in the engine compartment for the "K4" splice?
>
> Thanks,
> Kirk
> "Kirk Miller" <krik.rellim@comcast.net> wrote in message
> news:eCD7b.405661$YN5.273436@sccrnsc01...
> > Every sensor I checked, map, tps, & o2 had resistances of about 2.5 to 3.5
> > ohms from the ground pin to chassis. There is only .1 ohm resistance
> between
> > the negative terminal and the chassis ground on the fender well and the
> > negative terminal. Does the wire loom ground at the fender near the
> battery?
> >
> > I will check the resistance between the negative terminal and the engine.
> > The connection at the block doesn't look corroded. First I will have to
> > disconnect the ground I added. Have to save it for after work.....
> >
> > Thanks,
> > Kirk
> >
> > "DougW" <post.replies@invalid.address> wrote in message
> > news:puw7b.2510$8o3.918@news2.central.***.net...
> > > Kirk Miller wrote:
> > > > Well I finally crawled under the car with my DVM. I noticed I had
> about
> > 3.5
> > > > ohms of resistance to ground for the signal wire on the oxygen sensor.
> > I
> > > > looked at the electrical schematic in Haynes and it looks like all the
> > > > grounds are spliced at "K4" then grounded to chassis. I couldn't find
> > any
> > > > chassis grounds besides the one coming off the negative battery cable.
> > Is
> > > > there another location for the ground? What does a "K4" splice look
> like
> > and
> > > > what is it near?
> > > >
> > > > I spliced a wire on the MAP sensor ground and tied the wire to the
> > intake
> > > > manifold. My erratic idle has disappeared and check engine light
> hasn't
> > > > come on yet after 16 miles of driving. I think I might have found the
> > > > problem. I would like to fix the root problem though. Prior to adding
> > the
> > > > ground, the check engine light would come on every time I drove the
> car.
> > >
> > > 12 will happen if your battery is ever drained or disconnected or if
> > > the battery terminals are loose or corroded. It only resets after
> > > fifty, yes 50, starts.
> > >
> > > K4 isn't a description, just a numbering convention.
> > > It's located in the loom, passenger side of the engine
> > > block by the firewall. Outboard from where the oil pressure
> > > wires enter the loom.
> > >
> > > I would suspect a corroded pin in the O2 sensor connector
> > > before a break in the harness. Then again, check the resistance
> > > between the engine block and battery -. The I6 has a ground strap
> > > and if that is corroded all sorts of funky things come to play.
> > >
> > > --
> > > -- DougW -- 93 ZJ 4.0 http://members.***.net/wilsond
> > > HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
> > > Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
> > >
> > >
> > >
> >
> >

Mike Romain

I don't know the Grand, but can offer some ideas.

I believe the harness sensor grounds are tagged to the computer, could
be wrong, but there are a bunch of small black wires bolted to most
engine blocks somewhere near the oil sender that are for the 'computer'
signal/sensor grounds.

There also is one on the Cherokee up under the dash above the gas pedal
on the firewall. The YJ has one on the e-brake pedal housing too.

Most engines are also grounded to the firewall with a mesh cable. This
sucker likes to rot away and/or get corroded ends. It usually comes off
the top back of the head or off the bell housing and goes to the
firewall.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

Kirk Miller wrote:
>
> The resistance from negative terminal to engine is also 0.1 ohm. That means
> the resistance caused by some connection between the "K4" splice and the
> ground connection.
>
> Does anyone know where the chassis ground connection is physically located
> in the engine compartment for the "K4" splice?
>
> Thanks,
> Kirk
> "Kirk Miller" <krik.rellim@comcast.net> wrote in message
> news:eCD7b.405661$YN5.273436@sccrnsc01...
> > Every sensor I checked, map, tps, & o2 had resistances of about 2.5 to 3.5
> > ohms from the ground pin to chassis. There is only .1 ohm resistance
> between
> > the negative terminal and the chassis ground on the fender well and the
> > negative terminal. Does the wire loom ground at the fender near the
> battery?
> >
> > I will check the resistance between the negative terminal and the engine.
> > The connection at the block doesn't look corroded. First I will have to
> > disconnect the ground I added. Have to save it for after work.....
> >
> > Thanks,
> > Kirk
> >
> > "DougW" <post.replies@invalid.address> wrote in message
> > news:puw7b.2510$8o3.918@news2.central.***.net...
> > > Kirk Miller wrote:
> > > > Well I finally crawled under the car with my DVM. I noticed I had
> about
> > 3.5
> > > > ohms of resistance to ground for the signal wire on the oxygen sensor.
> > I
> > > > looked at the electrical schematic in Haynes and it looks like all the
> > > > grounds are spliced at "K4" then grounded to chassis. I couldn't find
> > any
> > > > chassis grounds besides the one coming off the negative battery cable.
> > Is
> > > > there another location for the ground? What does a "K4" splice look
> like
> > and
> > > > what is it near?
> > > >
> > > > I spliced a wire on the MAP sensor ground and tied the wire to the
> > intake
> > > > manifold. My erratic idle has disappeared and check engine light
> hasn't
> > > > come on yet after 16 miles of driving. I think I might have found the
> > > > problem. I would like to fix the root problem though. Prior to adding
> > the
> > > > ground, the check engine light would come on every time I drove the
> car.
> > >
> > > 12 will happen if your battery is ever drained or disconnected or if
> > > the battery terminals are loose or corroded. It only resets after
> > > fifty, yes 50, starts.
> > >
> > > K4 isn't a description, just a numbering convention.
> > > It's located in the loom, passenger side of the engine
> > > block by the firewall. Outboard from where the oil pressure
> > > wires enter the loom.
> > >
> > > I would suspect a corroded pin in the O2 sensor connector
> > > before a break in the harness. Then again, check the resistance
> > > between the engine block and battery -. The I6 has a ground strap
> > > and if that is corroded all sorts of funky things come to play.
> > >
> > > --
> > > -- DougW -- 93 ZJ 4.0 http://members.***.net/wilsond
> > > HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
> > > Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
> > >
> > >
> > >
> >
> >