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Unread 08-20-2013, 01:58 PM   #1
Registered User
1996 ZJ 
Join Date: May 2012
Location: Diberville, ms
Posts: 84
Diagnosing battery drain

I have been having intermittent stalling and no start problems, throwing codes 42 43(p0351) 72. The 72 low cat efficiency I have always had, the other 2 popped up recently.

I found out for sure problem is loss of spark. My battery was really, really dead. I got it charged to 12.4. With car running it goes to 13.78.

I'm a bit clueless as to how to diagnose battery drain. I have a voltmeter and continuity tester, but I'm not sure where to start.

I'm not good with electrical stuff. :/

1996 jeep grand cherokee laredo 2wd
240,xxx miles 4.0L i6
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Unread 08-20-2013, 02:47 PM   #2
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2000 TJ Wrangler 
Join Date: Jul 2012
Location: Boston, MA
Posts: 2,725
search the code numbers and then go from there as far as what they are...most have been covered somewhere on the site. Could also go to autozone or somewhere and have them read the codes to see what they are then start from there. I searched up 43 ignition control circuit not responding. I'm not good with electrical so someone else or maybe search around on that.

If i had to guess for a start. check all grounds and fuses and look from wires that are chewed, melted or stripped.
00 TJ "Fiona" 2.5" 35" Bajas, MC 6" Overline System, HPd30/8.8
95 ZJ 3.5" lift w/242 swap-Sold
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Unread 08-20-2013, 07:35 PM   #3
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1997 ZJ 
Join Date: Dec 2008
Location: , Alabama
Posts: 8,227
Addressing the code 42, If your gas gauge works good, look in the PDC (fusebox under the hood) and find the fuel pump and ASD relays. Swap them out with the horn and intermittent wiper relays (if your horn and wiper are working good)

42* Auto Shutdown Relay Control Circuit
An open or shorted condition detected in the auto shutdown relay circuit.
42* Fuel Pump Relay Control Circuit
An open or shorted condition detected in the fuel pump relay control circuit.\
42* Fuel Level Sending Unit Volts Too Low
Open circuit between PCM and fuel gauge sending unit.
Fuel Level Sending Unit Volts Too High
Circuit shorted to voltage between PCM and fuel gauge sending unit.
Fuel Level Unit No Change Over Miles
No movement of fuel level sender detected.
* Check Engine Lamp (MIL) will not illuminate if this Diagnostic Trouble Code was recorded. Cycle Ignition key as described in manual and observe code flashed by Check Engine lamp.

For the P0351, this is sometimes a problem in the coil or PCM, but may be caused by bad grounds. Usually accompanied by a miss.
P0351 Ignition Coil #1 Primary Circuit
Peak primary circuit current not achieved with maximum dwell time.

This could be caused by a lazy rear o2 sensor or bad cat.
72** P0420 Catalytic Efficency Failure
Catalyst efficiency below required level.
** Check Engine Lamp (MIL) will illuminate during engine operation if this Diagnostic Trouble Code was recorded.

If you in fact have a parasitic drain, it's usually caused by something connected to the body control module, most notably a door module or switch. You need to be sure your charging system is up to par before you start chasing a drain.

Check out the links in my sig and read over everything.
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