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Unread 11-01-2011, 07:00 AM   #1
petreyg
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p0320 trouble code. 2003 grand cherokee 4.7

Started out it would occasionally not start. Pulled a p0320 trouble code. I replaced the cam position sensor and the crank position sensor last night. I did get it started once before replacing these so the engine was warm. I noticed that it starts fine when warm. After replacing both sensors it started every time and ran great. This morning it was about 34 degrees and it will not start. Cranks over just fine.

Any ideas? I bought both sensors at autozone.

Thanks in advance. I have to drive to PA tomorrow and do not know what to do.

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Unread 11-01-2011, 03:24 PM   #2
ironmatt85
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Have you checked the battery condition? Cold battery, might give you a slow start...
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Unread 11-01-2011, 04:48 PM   #3
petreyg
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Battery was/is fine. Cranking over fast. I went to the dealership and bought the oem sensors crank and cam. Started right up. We'll see tomorrow morning after sitting all night.
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Unread 11-01-2011, 07:33 PM   #4
ironmatt85
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Good luck, hopefully nothing more than that.
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Unread 11-02-2011, 01:44 AM   #5
sanddrag
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Had the same issue here on a 2001. Replaced crank sensor several times, starts right up after being replaced and runs fantastic, several stops and starts. Let it sit overnight, next day it won't start. My next step is cam sensor. I really don't know what else it could be unless there's a continuity problem in some wiring or something.
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Unread 11-03-2011, 07:00 AM   #6
petreyg
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After replacing the cam and crank position aftermarket sensors with oem parts the problem went away. So far.... I heard that the cam and crank sensors work in tandem so when replacing one u should do the other.
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Unread 11-03-2011, 08:57 AM   #7
rm2001wj
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It's not true that both have to be replaced if only one is bad, but it surely won't hurt.
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Unread 11-03-2011, 10:35 AM   #8
keith20mm
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Quote:
Originally Posted by petreyg View Post
Started out it would occasionally not start. Pulled a p0320 trouble code. I replaced the cam position sensor and the crank position sensor last night. I did get it started once before replacing these so the engine was warm. I noticed that it starts fine when warm. After replacing both sensors it started every time and ran great. This morning it was about 34 degrees and it will not start. Cranks over just fine.

Any ideas? I bought both sensors at autozone.

Thanks in advance. I have to drive to PA tomorrow and do not know what to do.
Firstly, those sensors are pretty simple Hall-effect pickups, and they are basically a device potted in a brick of epoxy plastic.

I could vaguely envision a sensor connection internally broken, but I can easily and clearly envision a broken wire in the connector that connects to the sensor, or a wire break at the pin on the wire at the PCM... especially if the problem exhibits on deep temperature drops.

I could slightly envision a bad connector where the harness connects to the sensor... unlike Ford, which has the almost always failing connectors, Jeep's connectors are pretty good.

As to crankshaft and camshaft position sensor failures, what I've most often found is that simply disconnecting the connector hood, and reconnecting, maybe three times, often corrects the problem.

Again, the sensors are built like bricks... solid, and not very prone to failure.

Now, when one changes out a sensor, they surely disconnect the harness, then reconnect the harness, after changing out the sensor... Duh.... is it.. er... possible... uh... no, surely not... that just plugging and unplugging the connector is the ....uh... fix?
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Unread 05-05-2012, 07:12 PM   #9
petreyg
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Ok guys. Still pulling p0320 and p0725 codes.

Heard that it may be speed sensors causing the codes since both cam and crank sensors have already been replaced with oem parts. I have a 2003 jeep grand cherokee limited 4.7 not a high output. Quadra drive.

The drivers side of the tranny has 2 sensors front and back. Both black. They look similar to the cam and crank sensors.

Any help would be appreciated.
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Unread 05-05-2012, 07:22 PM   #10
sanddrag
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On mine it turned out to be the wiring harness to the crankshaft position sensor. It looked totally fine, and even metered out fine, but on occasion would provide an intermittent connection.
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Unread 05-05-2012, 08:25 PM   #11
petreyg
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Thanks so much. Refresh my memory.

Is that the one above the starter or on the passenger side of the engine from the bottom. How hard was it to replace the wiring harness? Could heat be causing it?
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Unread 05-05-2012, 09:32 PM   #12
rm2001wj
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Sorry to have to tell you, but that P0725 = Engine Speed Input Circuit, is not related to any tranny speed sensor. It is the crankshaft position sensor signal that the PCM uses to get the engine speed. It looks like there is still a problem with the crankshaft position sensor and/or the wiring harness connector. That sensor is the one located above the starter.
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Unread 05-07-2012, 04:50 PM   #13
petreyg
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Thanks a lot everyone. How hard was the wiring harness to the crank position sensor to replace?
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Unread 05-31-2012, 09:55 AM   #14
petreyg
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Ok everyone, here is an update. I drove the jeep for about a week (short trips) without issue. I went to PA last weekend, drove approx 75 miles, Stopped for gas. When I went to start it back up it threw a p0320 code again. Started but ran like crap and the check engine light was on. The symptoms are always that it wont start or starts and runs badly. Anything thing over 3000 rpms causes it to miss and sputter. I cleared the code and restarted the jeep.. same problem.

I pulled the positive battery terminal for 20 minutes. After that the code went away and ran fine with no miss or sputter until the next time I turned it off and restarted it.

The cam and cranp positions sensors were replaced in December with OEM parts. Someone mentioned the wiring harness.

How hard is this to replace for the crank sensor? The fuel pump was replaced last may, but could a faulty fuel pump cause the p0320 code? I also heard this code points to the throttle position sensor.

Any ideas would help. I'm at a loss.
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Unread 07-14-2012, 02:18 PM   #15
petreyg
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Update.

It was the wiring harness to the crank position sensor.

Took 3 people to troubleshoot.
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