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jd4010 09-22-2010 11:05 AM

Sensor on battery tray
1999 Grand Cherokee Laredo 4.0

Last night I was removing the battery, battery tray, fuse box, etc to get to and replace the fan relay when something struck me as interesting. On the bottom of the battery tray is a sensor of some sort. It appears to be spring loaded and held down by the battery. What is this for?

Inquiring minds want to know. :)

hemi.jon 09-22-2010 12:13 PM

Re: Sensor on battery tray
i never really found much of an answer to this, mine broke out of my TJ and never gave me a code or light or anything.

georgeda 09-22-2010 12:37 PM

Re: Sensor on battery tray
Its the batery temperature sensor. When the battery is very cold it will receive a higher rate of charge.

jd4010 09-22-2010 02:28 PM

Re: Sensor on battery tray
Now that is pretty cool! Thank you for the info.

Frango100 09-22-2010 02:51 PM

Re: Sensor on battery tray
Just as an add on, what the Jeep manual says:

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
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 degrees F.

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