98 xlt 4.0 sohc temp gauge messing up

[Omarzer00]

Hello,
this could have been asked before but I couldn’t find an exact answer.
My 98 xlt 4.0 sohc temp gauge all of the sudden went up all the way to H and check gauge light turned on. the car is not overheating I checked the fan and coolant is it the thermostat or the sensors? where should I start the troubleshooting? I see two sensors behind the thermostat housing which one I need to check? and how tell if my gauge is bad is there away to test with voltmeter?
Thanks

 

[Pete Deering]

Hello,
this could have been asked before but I couldn’t find an exact answer.
My 98 xlt 4.0 sohc temp gauge all of the sudden went up all the way to H and check gauge light turned on. the car is not overheating I checked the fan and coolant is it the thermostat or the sensors? where should I start the troubleshooting? I see two sensors behind the thermostat housing which one I need to check? and how tell if my gauge is bad is there away to test with voltmeter?
Thanks

There is a sensor just for the gauge. When you ground the gauge wire it will go to H. If disconnect the wire from the sensor ( open circuit) will go to L or below. That is the simplest way to test it.
So your gauge wire is shorted . so just disconnect the wire from the sensor, and see what happens
The sensor goes go bad. My did, not read right. I just replaced the sensor. Its around $30.
If you have a live data scanner, you can just read the temperature.

 

[Omarzer00]

There is a sensor just for the gauge. When you ground the gauge wire it will go to H. If disconnect the wire from the sensor ( open circuit) will go to L or below. That is the simplest way to test it.
So your gauge wire is shorted . so just disconnect the wire from the sensor, and see what happens
The sensor goes go bad. My did, not read right. I just replaced the sensor. Its around $30.
If you have a live data scanner, you can just read the temperature.

I have one and just drove the car while the live data scanner is connected it was reading 168F after 20 minutes of drive. The gauge went just little bit under the red line for H does this means the sender is good? I also turned on the heat and there was a hot air coming in which means the thermostat is good too I guess?

 

[Pete Deering]

I have one and just drove the car while the live data scanner is connected it was reading 168F after 20 minutes of drive. The gauge went just little bit under the red line for H does this means the sender is good? I also turned on the heat and there was a hot air coming in which means the thermostat is good too I guess?

That shows that the sensor for the gauge is bad.
( nothing reading correctly). The H mark should be 212°F.

The heater and thermostat are working properly. They are both additional circuit. They Both have nothing to do with the temperature gauge.

The only common denominator is the engine coolant. They all use engine coolant for their results.
Your scan tool is telling You, what the coolant temperature is.
The coolant is at 168°F. The thermostat is closed no coolant flow, till 195°F. The heater core has very little coolant flow thru it, Because the thermostat is closed, only vent hole.

 

[eddiehudson]

After a 20 minute drive the temperature should be more than 168 degrees. Maybe the thermostat is missing?

 

[Omarzer00]

After a 20 minute drive the temperature should be more than 168 degrees. Maybe the thermostat is missing?

168 degree I think the gauge should point somewhere between 1/4 to 1/2. above 200 degree should point to the H zone. if the if I turn the heat on I am getting hot air so I was guessing the thermostat is Ok too

 

[Omarzer00]

That shows that the sensor for the gauge is bad.
( nothing reading correctly). The H mark should be 212°F.

The heater and thermostat are working properly. They are both additional circuit. They Both have nothing to do with the temperature gauge.

The only common denominator is the engine coolant. They all use engine coolant for their results.
Your scan tool is telling You, what the coolant temperature is.
The coolant is at 168°F. The thermostat is closed no coolant flow, till 195°F. The heater core has very little coolant flow thru it, Because the thermostat is closed, only vent hole.

thanks Pete,
since I see 2 sensors behind the thermostat and I am getting realistic temperature readings using the live scanner. does it means the sensor that connected to the car ECM is good and I should focus on the other one that goes to the gauge.
I am going to disconnect the sensor that going to the gauge and turn on the key. the needle should go down right? If not then its the gauge itself fault? I am just trying to set a plan to diagnose the issue.

 

[Pete Deering]

thanks Pete,
since I see 2 sensors behind the thermostat and I am getting realistic temperature readings using the live scanner. does it means the sensor that connected to the car ECM is good and I should focus on the other one that goes to the gauge.
I am going to disconnect the sensor that going to the gauge and turn on the key. the needle should go down right? If not then its the gauge itself fault? I am just trying to set a plan to diagnose the issue.

1. I don't know , which sensor is which. They are both two wire sensor. ( I try to help another member, post the part pictures)
2.? does it means the sensor that connected to the car ECM is good. YES
3. focus on the other one that goes to the gauge. Yes
4. ? disconnect the sensor that going to the gauge and turn on the key. the needle should Not move at or below L. and turn on the key
5. If you jump the terminals inside the connector it should go above H.and turn on the key
Step 4 &5, also test the wiring. If the needle stay at L , when disconnected, and go too H when grounded.
See this post. # 206 1997 "white" 4.0 SOHC primary and D side secondary chain guide repair-Fill neck hose replace-

 

[eddiehudson]

Omar you never said what the code was when the check engine light comes on.

 

[Omarzer00]

Omar you never said what the code was when the check engine light comes on.

I don’t have a check engine light on. the “check gauge” light is on

 

[donalds]

The gray 1 is for the PCM the brown 1 is for the gauge

 

[eddiehudson]

I don’t have a check engine light on. the “check gauge” light is on

I may be wrong but I think you can read it as a Global DTC.

 

[Omarzer00]

1. I don't know , which sensor is which. They are both two wire sensor. ( I try to help another member, post the part pictures)
2.? does it means the sensor that connected to the car ECM is good. YES
3. focus on the other one that goes to the gauge. Yes
4. ? disconnect the sensor that going to the gauge and turn on the key. the needle should Not move at or below L. and turn on the key
5. If you jump the terminals inside the connector it should go above H.and turn on the key
Step 4 &5, also test the wiring. If the needle stay at L , when disconnected, and go too H when grounded.
See this post. # 206 1997 "white" 4.0 SOHC primary and D side secondary chain guide repair-Fill neck hose replace-

Hello again Pete
are these sensors screwed in or pushed in if I need to remove them?

 

[Pete Deering]

Hello again Pete
are these sensors screwed in or pushed in if I need to remove them?

The sensor is threaded in. The body is tapered. , so don't over tighten.

 

[410Fortune]

98 sohc engine the temp sensors are held in with clips into the thermostat housing, not threaded in

 

[donalds]

Prepare to buy a nice new metal thermostat housing with sensor s

Like this post if you've been there lol

 

[Omarzer00]

Hello,
this could have been asked before but I couldn’t find an exact answer.
My 98 xlt 4.0 sohc temp gauge all of the sudden went up all the way to H and check gauge light turned on. the car is not overheating I checked the fan and coolant is it the thermostat or the sensors? where should I start the troubleshooting? I see two sensors behind the thermostat housing which one I need to check? and how tell if my gauge is bad is there away to test with voltmeter?
Thanks

I could not reach it looks like I have to remove the thermostat