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

Re: 97 Grand - Fault code 12 a problem?
 

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!

Re: 97 Grand - Fault code 12 a problem?
 

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!

Re: 97 Grand - Fault code 12 a problem?
 

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!

Re: 97 Grand - Fault code 12 a problem?
 

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

Re: 97 Grand - Fault code 12 a problem?
 

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

Re: 97 Grand - Fault code 12 a problem?
 

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

Re: 97 Grand - Fault code 12 a problem?
 

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

Re: 97 Grand - Fault code 12 a problem?
 

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

Re: 97 Grand - Fault code 12 a problem?
 

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