97 Grand - Fault code 12 a problem?

I have a 1997 Grand Cherokee Limited 4.0L. I have been having stalling
problems (fault code 43 / reader P0351) that the mechanic is working on.
When the 43/P0351 code has been cleared, the odometer codes (read with
on-off-on-off-on) show 12-55. I know 55 means end of codes, but I have seen
multiple explanations for code 12. Some say it means start of codes. Others
say it means loss of power recently -- usually a disconnected battery.

What does code 12 mean?

If it means some fault, does it have an equivalent code that the readers
show (e.g. P0351)? My mechanic's reader shows no code other than the P0351
that appears after a stalling problem.

Some say the code 12 should disappear after 15 ignition on-off cycles. I
have tried many more than 15 cycles and the code remains. Is this a sign of
problems? Could the problem cause intermittent stalling problems? Could a
code 12 problem lead to the conditions that set code 43/P0351?

Thanks for any information. I am reasonably technical, but I have little
experience with car mechanical work.

Joe M

Joe_M wrote:
> I have a 1997 Grand Cherokee Limited 4.0L. I have been having stalling
> problems (fault code 43 / reader P0351) that the mechanic is working
> on. When the 43/P0351 code has been cleared, the odometer codes (read
> with on-off-on-off-on) show 12-55. I know 55 means end of codes, but
> I have seen multiple explanations for code 12. Some say it means
> start of codes. Others say it means loss of power recently -- usually
> a disconnected battery.
> What does code 12 mean?

The battery has been disconnected (or the ECU lost power) within the last
50 starts. (basically it's a meaningless code unless accompanied by a lot
of others in which case it means to check for loose battery cables)

As for 43, Peak primary circuit current not achieved with maximum
dwell time.

That basically means the coil is having problems. Likely you need
a new coil.

Stalling/rough idle is usually caused by a clogged up IAP (Idle Air
Passage) and IAC (Idle Air Controller) in the throttle body. Although
stalls can also be caused by a failing CPS (Crankshaft Position Sensor)
and that fault may or may not set a code. Usually it doesn't. Just
got through replacing mine after a stall at stop issue.


--
-- DougW -- 93 ZJ 4.0 http://revbeergoggles.com
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
Banks Header - and BEER, in the fridge!

I would suspect the battery cable connections are corroded which will
set the code 12 and trigger the low power to coil problem.

Don't forget that the battery cables have 2 ends... The ground is a
sneaky one for being bad.

If you have recently had the battery disconnected, then my guess might
be off and you are only having coil or it's connection issues. The
connections on them can get corroded too.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

Joe_M wrote:
>
> I have a 1997 Grand Cherokee Limited 4.0L. I have been having stalling
> problems (fault code 43 / reader P0351) that the mechanic is working on.
> When the 43/P0351 code has been cleared, the odometer codes (read with
> on-off-on-off-on) show 12-55. I know 55 means end of codes, but I have seen
> multiple explanations for code 12. Some say it means start of codes. Others
> say it means loss of power recently -- usually a disconnected battery.
>
> What does code 12 mean?
>
> If it means some fault, does it have an equivalent code that the readers
> show (e.g. P0351)? My mechanic's reader shows no code other than the P0351
> that appears after a stalling problem.
>
> Some say the code 12 should disappear after 15 ignition on-off cycles. I
> have tried many more than 15 cycles and the code remains. Is this a sign of
> problems? Could the problem cause intermittent stalling problems? Could a
> code 12 problem lead to the conditions that set code 43/P0351?
>
> Thanks for any information. I am reasonably technical, but I have little
> experience with car mechanical work.
>
> Joe M

Mike Romain wrote:
> I would suspect the battery cable connections are corroded which will
> set the code 12 and trigger the low power to coil problem.
>
> Don't forget that the battery cables have 2 ends... The ground is a
> sneaky one for being bad.
>
> If you have recently had the battery disconnected, then my guess might
> be off and you are only having coil or it's connection issues. The
> connections on them can get corroded too.

FWIW, the ground strap on ZJs is not the metal braid type. It runs
between the battery and the forward lug that holds the coil to the
block. A secondary cable from the battery ground runs to the chassis
ground point on the passenger front fender.

For a 97 I'm still betting the coil is shot.

--
DougW

Doug and Mike,

Thanks for your replies.

So far the coil and crank position sensor have been replaced with no
improvement. The car intermittently stalls (or cuts out) at speed or idle.
If at speed it often will pick back up again in a second or two with no
backfire. If the car is stopped it usually starts again on the first crank.
Sometimes it has taken 3 or 4 cranks and a minute or two. Always have strong
cranks. The mechanic has gone over the wiring and not found anything. These
stalls/cut-outs happen rarely -- say once a week or so. I feel fairly
comfortable driving the car around town.

If I get codes 12-55, does that _just_ mean that the battery was
disconnected in the last 50 cycles? I never got any longer code that
appeared on a code reader (ODB or ODB-II?) for the 12 code. I did get a
P0351 for the 43 code. If there is any ongoing battery connection issue,
should I see something other than 12 on the jeep codes or should I also see
something on one of those code readers.

By ignition cycle, do you mean turning the car on-off (as in two quick
cycles plus an on initiates the fault codes) or do I have to actually start
the engine? Should I be able to clear the 12 code by just doing 50 quick
on-offs?

Thanks,

Joe M

"DougW" > wrote in message
...
> Mike Romain wrote:
>> I would suspect the battery cable connections are corroded which will
>> set the code 12 and trigger the low power to coil problem.
>>
>> Don't forget that the battery cables have 2 ends... The ground is a
>> sneaky one for being bad.
>>
>> If you have recently had the battery disconnected, then my guess might
>> be off and you are only having coil or it's connection issues. The
>> connections on them can get corroded too.
>
> FWIW, the ground strap on ZJs is not the metal braid type. It runs
> between the battery and the forward lug that holds the coil to the
> block. A secondary cable from the battery ground runs to the chassis
> ground point on the passenger front fender.
>
> For a 97 I'm still betting the coil is shot.
>
> --
> DougW
>

Be sure, if you decide to get a new coil, to buy an original chrysler part.
I bought an aftermarket, and my jeep, after installing it, would stall after
becoming hot. The connection on the coil was expanding, and at that point,
the connection was lost. I tried 2 aftermarket coils and both behaved the
same way. After installing a factory coil, I have had no problems.

cal

"Joe_M" > wrote in message
news
> Doug and Mike,
>
> Thanks for your replies.
>
> So far the coil and crank position sensor have been replaced with no
> improvement. The car intermittently stalls (or cuts out) at speed or idle.
> If at speed it often will pick back up again in a second or two with no
> backfire. If the car is stopped it usually starts again on the first
> crank. Sometimes it has taken 3 or 4 cranks and a minute or two. Always
> have strong cranks. The mechanic has gone over the wiring and not found
> anything. These stalls/cut-outs happen rarely -- say once a week or so. I
> feel fairly comfortable driving the car around town.
>
> If I get codes 12-55, does that _just_ mean that the battery was
> disconnected in the last 50 cycles? I never got any longer code that
> appeared on a code reader (ODB or ODB-II?) for the 12 code. I did get a
> P0351 for the 43 code. If there is any ongoing battery connection issue,
> should I see something other than 12 on the jeep codes or should I also
> see something on one of those code readers.
>
> By ignition cycle, do you mean turning the car on-off (as in two quick
> cycles plus an on initiates the fault codes) or do I have to actually
> start the engine? Should I be able to clear the 12 code by just doing 50
> quick on-offs?
>
> Thanks,
>
> Joe M
>
> "DougW" > wrote in message
> ...
>> Mike Romain wrote:
>>> I would suspect the battery cable connections are corroded which will
>>> set the code 12 and trigger the low power to coil problem.
>>>
>>> Don't forget that the battery cables have 2 ends... The ground is a
>>> sneaky one for being bad.
>>>
>>> If you have recently had the battery disconnected, then my guess might
>>> be off and you are only having coil or it's connection issues. The
>>> connections on them can get corroded too.
>>
>> FWIW, the ground strap on ZJs is not the metal braid type. It runs
>> between the battery and the forward lug that holds the coil to the
>> block. A secondary cable from the battery ground runs to the chassis
>> ground point on the passenger front fender.
>>
>> For a 97 I'm still betting the coil is shot.
>>
>> --
>> DougW
>>
>
>

I finally replaced the computer and the problem stopped. Later I developed a
new problem where the engine would not start after being driven and then
parked for about 1/2 hour. No codes. I have questions, but a new post under
"97 Grand fuel pump relay killed fuel pump?"

Joe M

"Cal" > wrote in message
...
> Be sure, if you decide to get a new coil, to buy an original chrysler
> part. I bought an aftermarket, and my jeep, after installing it, would
> stall after becoming hot. The connection on the coil was expanding, and at
> that point, the connection was lost. I tried 2 aftermarket coils and both
> behaved the same way. After installing a factory coil, I have had no
> problems.
>
> cal
>
> "Joe_M" > wrote in message
> news
>> Doug and Mike,
>>
>> Thanks for your replies.
>>
>> So far the coil and crank position sensor have been replaced with no
>> improvement. The car intermittently stalls (or cuts out) at speed or
>> idle. If at speed it often will pick back up again in a second or two
>> with no backfire. If the car is stopped it usually starts again on the
>> first crank. Sometimes it has taken 3 or 4 cranks and a minute or two.
>> Always have strong cranks. The mechanic has gone over the wiring and not
>> found anything. These stalls/cut-outs happen rarely -- say once a week or
>> so. I feel fairly comfortable driving the car around town.
>>
>> If I get codes 12-55, does that _just_ mean that the battery was
>> disconnected in the last 50 cycles? I never got any longer code that
>> appeared on a code reader (ODB or ODB-II?) for the 12 code. I did get a
>> P0351 for the 43 code. If there is any ongoing battery connection issue,
>> should I see something other than 12 on the jeep codes or should I also
>> see something on one of those code readers.
>>
>> By ignition cycle, do you mean turning the car on-off (as in two quick
>> cycles plus an on initiates the fault codes) or do I have to actually
>> start the engine? Should I be able to clear the 12 code by just doing 50
>> quick on-offs?
>>
>> Thanks,
>>
>> Joe M
>>
>> "DougW" > wrote in message
>> ...
>>> Mike Romain wrote:
>>>> I would suspect the battery cable connections are corroded which will
>>>> set the code 12 and trigger the low power to coil problem.
>>>>
>>>> Don't forget that the battery cables have 2 ends... The ground is a
>>>> sneaky one for being bad.
>>>>
>>>> If you have recently had the battery disconnected, then my guess might
>>>> be off and you are only having coil or it's connection issues. The
>>>> connections on them can get corroded too.
>>>
>>> FWIW, the ground strap on ZJs is not the metal braid type. It runs
>>> between the battery and the forward lug that holds the coil to the
>>> block. A secondary cable from the battery ground runs to the chassis
>>> ground point on the passenger front fender.
>>>
>>> For a 97 I'm still betting the coil is shot.
>>>
>>> --
>>> DougW
>>>
>>
>>
>
>

You are still describing a code 12 issue I think.....

I would be making 'really' sure the body of the vehicle had full power.

To do this, I take a multimeter and read the volts at the battery posts
with the engine running and the headlights and heater fan and wipers on.
I then move the negative meter probe to the body with the positive
still on the battery positive and compare the voltages.

If the voltages are different, your body ground path is bad.

Good luck!

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's - Gone to the rust pile...
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

Joe_M wrote:
> I finally replaced the computer and the problem stopped. Later I developed a
> new problem where the engine would not start after being driven and then
> parked for about 1/2 hour. No codes. I have questions, but a new post under
> "97 Grand fuel pump relay killed fuel pump?"
>
> Joe M
>
> "Cal" > wrote in message
> ...
>> Be sure, if you decide to get a new coil, to buy an original chrysler
>> part. I bought an aftermarket, and my jeep, after installing it, would
>> stall after becoming hot. The connection on the coil was expanding, and at
>> that point, the connection was lost. I tried 2 aftermarket coils and both
>> behaved the same way. After installing a factory coil, I have had no
>> problems.
>>
>> cal
>>
>> "Joe_M" > wrote in message
>> news
>>> Doug and Mike,
>>>
>>> Thanks for your replies.
>>>
>>> So far the coil and crank position sensor have been replaced with no
>>> improvement. The car intermittently stalls (or cuts out) at speed or
>>> idle. If at speed it often will pick back up again in a second or two
>>> with no backfire. If the car is stopped it usually starts again on the
>>> first crank. Sometimes it has taken 3 or 4 cranks and a minute or two.
>>> Always have strong cranks. The mechanic has gone over the wiring and not
>>> found anything. These stalls/cut-outs happen rarely -- say once a week or
>>> so. I feel fairly comfortable driving the car around town.
>>>
>>> If I get codes 12-55, does that _just_ mean that the battery was
>>> disconnected in the last 50 cycles? I never got any longer code that
>>> appeared on a code reader (ODB or ODB-II?) for the 12 code. I did get a
>>> P0351 for the 43 code. If there is any ongoing battery connection issue,
>>> should I see something other than 12 on the jeep codes or should I also
>>> see something on one of those code readers.
>>>
>>> By ignition cycle, do you mean turning the car on-off (as in two quick
>>> cycles plus an on initiates the fault codes) or do I have to actually
>>> start the engine? Should I be able to clear the 12 code by just doing 50
>>> quick on-offs?
>>>
>>> Thanks,
>>>
>>> Joe M
>>>
>>> "DougW" > wrote in message
>>> ...
>>>> Mike Romain wrote:
>>>>> I would suspect the battery cable connections are corroded which will
>>>>> set the code 12 and trigger the low power to coil problem.
>>>>>
>>>>> Don't forget that the battery cables have 2 ends... The ground is a
>>>>> sneaky one for being bad.
>>>>>
>>>>> If you have recently had the battery disconnected, then my guess might
>>>>> be off and you are only having coil or it's connection issues. The
>>>>> connections on them can get corroded too.
>>>> FWIW, the ground strap on ZJs is not the metal braid type. It runs
>>>> between the battery and the forward lug that holds the coil to the
>>>> block. A secondary cable from the battery ground runs to the chassis
>>>> ground point on the passenger front fender.
>>>>
>>>> For a 97 I'm still betting the coil is shot.
>>>>
>>>> --
>>>> DougW
>>>>
>>>
>>
>
>