Jimh64

When u start my Jeep, the temperature gauge does not work. All of the other gauges appear to be working fine.

I checked the sensor and the wires are not broken.

Is there away that I can test the sensor to see if it is faulty?

Thanks!

DeadCellM60

Not that I know of but the fact that it isn't doing its job is a good indicator that it's busted. A new one is like $20 at your average big box store.

ol"blue

Apparently it's not getting hot or the "Check Engine" light would have gone off. If it was running too cool, as if it had a lower than listed temp thermostat, or not one at all, it would have set off a Check Engine light and stored a code. The ZJ I had did this for an improper thermostat.
Maybe you can try unplugging the switch and see what affect it has on the gauge, if it moves or not.
Te following comes from the ZJ Factory Service Manual:
DIAGNOSIS AND TESTING
ON-BOARD DIAGNOSTICS (OBD)
FOR CERTAIN COOLING SYSTEM
COMPONENTS
The powertrain control module (PCM) has been
programmed to monitor certain cooling system components:
NOTE: If the engine has remained cool for too long
a period, such as with a stuck open thermostat, a
Diagnostic Trouble Code (DTC) number 17 can be
observed at the malfunction indicator lamp. This
lamp is displayed on the instrument panel as the
CHECK ENGINE lamp (Fig. 14).
If the problem is sensed in a monitored circuit
often enough to indicate an actual problem, a DTC is
stored. The DTC will be stored in the PCM memory
for eventual display to the service technician. If the
problem is repaired or ceases to exist, the PCM cancels
the DTC after 51 engine starts.
Certain criteria must be met for a DTC to be
entered into PCM memory. The criteria may be a
specific range of engine rpm, engine temperature
and/or input voltage to the PCM.
A DTC indicates that the PCM has recognized an
abnormal signal in a circuit or the system. A DTC
may indicate the result of a failure, but never identify
the failed component directly.
It is possible that a DTC for a monitored circuit
may not be entered into memory even though a malfunction
has occurred. Refer to On- Board Diagnostics
(OBD) in Group 25, Emission Control Systems
for additional information.
ACCESSING DIAGNOSTIC TROUBLE CODES
A stored Diagnostic Trouble Code (DTC) can be displayed
by cycling the ignition key On-Off-On-Off-On
within three seconds and observing the malfunction
indicator lamp. This lamp is displayed on the instrument
panel as the CHECK ENGINE lamp (Fig. 14).
They can also be displayed through the use of the
Diagnostic Readout Box (DRB) scan tool. The DRB
connects to the data link connector, left of the steering
column above the brake pedal (Fig. 15). For operation
of the DRB, refer to the appropriate Powertrain
Diagnostic Procedures service manual.
EXAMPLES:
² If the lamp (Fig. 14) flashes 1 time, pauses and
flashes 2 more times, a flashing Diagnostic Trouble
Code (DTC) number 12 is indicated. If this code is
observed, it is indicating that the battery has been
disconnected within the last 50 key-on cycles. It
could also indicate that battery voltage has been disconnected
to the PCM. In either case, other DTC’s
may have been erased.
² If the lamp flashes 1 time, pauses and flashes 7
more times, a flashing Diagnostic Trouble Code
(DTC) number 17 is indicated.
After any stored DTC information has been
observed, the display will end with a flashing DTC
number 55. This will indicate the end of all stored
information.
ERASING TROUBLE CODES
After the problem has been repaired, use the DRB
scan tool to erase a DTC. Refer to the appropriate
Powertrain Diagnostic Procedures service manual for
operation of the DRB scan tool

Jimh64

I see there are two sensors. One on the thermostat housing and one in the back of the engine. Which one would control the gauge on my dashboard? It is dead, doesn't move one direction or another when starting the engine.

I will try pulling the codes tonight.

Thanks!

DeadCellM60

The one on the Thermostat Housing is the one you want.

Jimh64

thanks, but if that is the case what does the other 1 do, I'm just curious

ol"blue

It tells the PCM what temp the engine is, so it can control fuel and ignition settings, among other things.