97 Grand - Fault code 12 a problem?

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.

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 >

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.

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

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

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

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 > I finally replaced the computer and the problem stopped. Later I developed a