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Unread 12-29-2007, 08:19 PM   #1
headpro2
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Jeep Error Code P1492 - Ambient/Battery Temp Sensor

Hi Guys...I have a 2001 Jeep Grand Cherokeew/ 4.7 liter engine that runs very well. Have owned since new and never had any major issues with it (knock on wood). It currently has 140,000 miles, most of which are true hwy miles, and runs very strong. Doesn't use a drop of oil between changes either.

Problem is I get a P1492 error code and do not know what that means or involves. Like I said, the Jeep runs great...but I do need to get it inspected and can't until I get the light to go off. I did search and find another post about this very code, but no fix was provided.

Can anyone tell me what to look for and how to proceed? Thanks in advance!

Tom


Last edited by headpro2; 12-29-2007 at 08:34 PM..
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Unread 12-29-2007, 08:51 PM   #2
magneticred
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Check this link:

http://en.allexperts.com/q/Jeep-785/...sor-engine.htm

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Unread 12-29-2007, 09:48 PM   #3
headpro2
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Thanks magneticred! I checked the battery trey and found that my sensor was missing! The connector for the sensor was there...but no sensor! I guess that's what I get for letting the Advance Auto dude change my battery for me...not that I would have noticed...
I will purchase new sensor and post results.

Thanks again!
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Unread 12-29-2007, 10:06 PM   #4
headpro2
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I'm curious...is there any way to bypass the bettery temperature sensor and fool the computer into thinking it's installed?
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Unread 12-29-2007, 10:39 PM   #5
blovingier
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Sure there's a way to bypass the Battery Temperature Sensor just like everything else if you want to put the effort in. My question is why would you want to? That sensor is there to tell the PCM when to shut off current from the Electronic Voltage Regulator so your battery doesn't overheat.
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Unread 12-29-2007, 10:45 PM   #6
greasefingers
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Over charging on Jeeps is very rare and I doubt if the temp sensor can actually sense this. I have never ever seen a temp sensor on any vehicle except some jeeps. My ZJ did not come with one.

You would need a resistor of the correct ohms to fake it out.
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88 Cherokee 2-door with 5speed manual 139K miles(deceased) purchased new
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Unread 12-29-2007, 11:01 PM   #7
headpro2
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Just in case anyone ever has this problem...I found the following information...
the battery temp sensor part # is: 56027332 and should be around $30-$40

as far as i know that's a dealer only item.

here is a Description and Operation that i pulled from my alldata, and the last part of it also describes it's influence on your 1495 code.


Description and Operation

The Battery Temperature Sensor (BTS) is attached to the battery tray located under the battery.

The BTS is used to determine the battery temperature and control battery charging rate. This temperature data, along with data from monitored line voltage, is used by the PCM to vary the battery charging rate. System voltage will be higher at colder temperatures and is gradually reduced at warmer temperatures.

The PCM sends 5 volts to the sensor and is grounded through the sensor return line. As temperature increases, resistance in the sensor decreases and the detection voltage at the PCM increases.

The BTS is also used for OBD II diagnostics. Certain faults and OBD II monitors are either enabled or disabled, depending upon BTS input (for example, disable purge and enable Leak Detection Pump (LDP) and O2 sensor heater tests). Most OBD II monitors are disabled below 20 F

Thanks to this information, I now understand the purpose of the sensor...just as Blovingier has stated...it prevents overcharge and overheat...but more importantly, the BTS is also used for other diagnostics...so best not to tamper with.

Hope this helps the next guy/gal who runs into this problem.

Thanks again guys...TT
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Unread 12-29-2007, 11:02 PM   #8
muddyjgc
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The temp sensor is there to help tell the PCM how much to charge the batt. If a batt is cold it's going to need more juice from the alt. to maintain a charge than if it is warm, and to prevent overheating a batt when it is hot.

On Edit: Dang it looks like headpro2 was typing at the same time and beat me to it!
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Unread 12-29-2007, 11:06 PM   #9
headpro2
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It's just nice to be on the same page as you guys!!!

TT
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Unread 12-29-2007, 11:07 PM   #10
greasefingers
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Yea I would have to agree with you after thinking about it once more. The reason is: if the PCM uses it as part of a calculation; then it is necessary for it to be there. I am just glad that mine does not have it. One more thing to possibly go awry.
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94 Black Laredo 4-Liter with QuadraTrac (42RE trans & NP249 TC) 200,000 + miles purchased new

88 Cherokee 2-door with 5speed manual 139K miles(deceased) purchased new
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