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I have a 2008 Veracruz with a temperature gauge that is not working and both Radiator and Condenser Fans running constantly. Had a P0015 code, since cleared. The gauge did work briefly and showed vehicle at normal operating temp. All other gauges and dash accessories function properly. I have replaced the Temp Sensor. I tested resistance on old temp sensor and it works as well(at least I have a new sensor now). At the connector I have 5V on one pin and ground on the other pin. I removed both the fan relays in order to allow the coolant temp to increase and gauge still reads nothing. I'm not experiencing a rough idle or anything and vehicle seems to run and drive fine.

I'm thinking that the ECM is receiving the input from the temp sensor because the pin readings at the connector are accurate and there is no rough idle when engine is warm or cold. But the output from the ECM to the temp gauge may be faulty. Could this cause the fans to run constantly? Also is there a way to test the Temperature gauge circuit? Does anyone have a wiring schematic for what I'm looking at?
 

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I'm thinking that the ECM is receiving the input from the temp sensor because the pin readings at the connector are accurate and there is no rough idle when engine is warm or cold.
The fact that fans are running constantly suggests the ECM is not receiving input from the coolant temperature sensor. When the sensor signal is implausible the PCM switches the fans on as a fail safe measure to protect the engine from over heating.

MattW78 said:
But the output from the ECM to the temp gauge may be faulty.
I''m not familiar with the Veracruz, but the ECM doesn't usually control the gauge.

MattW78 said:
Also is there a way to test the Temperature gauge circuit?
Yes. Just read the sensor output using the live data function of an OBD scan tool. But I suspect you'll find the temperature is implausibly low. Which usually means the sensor circuit is open.

Are you sure you replaced the correct sensor? As I said, I'm not familiar with the Veracruz. But Hyundai coolant temperature sensors usually have 3 terminals. 2 are for the PCM sensor, and the 3rd is for the gauge sensor. A two terminal sensor is usually the oil temperature.

EDIT : See link below for a photo showing the location of the oil & coolant temperature sensors on 3.8 engine.



If I helped you fix it, why not...

Your support is greatly appreciated
 

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Pages on the cooling system start here;
Hyundai Workshop Manuals > Veracruz FWD V6-3.8L (2009) > Engine, Cooling and Exhaust > Cooling System > Radiator Cooling Fan > Radiator Cooling Fan Motor Relay > Component Information > Locations

Hyundai Workshop Manuals > Veracruz FWD V6-3.8L (2009) > Sensors and Switches > Sensors and Switches - Cooling System > Engine - Coolant Temperature Sensor/Switch > Coolant Temperature Sensor / Switch HVAC > Component Information > Locations

This should give you lots to read up on.
Workshop manuals is best viewed with an alternate browser or you find yourself in popup 👿.
I could not find the pages that cover the gauge, but I suspect it get signals from the Body Control Module.

I suspect you have a faulty ground. Because it worked for a bit, and then it didn't again. Grounding points are EVERYWHERE on the Veracruz.
I have not found a good map that shows all of the Veracruz's ground locations.


Good luck, -PC

You don't need you to buy me a coffee. 😏
 

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Pages on the cooling system start here
Thanks for sharing. I notice the diagram confirms the coolant sensor has three terminals...
Rectangle Font Parallel Number Diagram


PinCup said:
I suspect you have a faulty ground.
FWIW, that seems unlikely given that the two temperature sensors (PCM & gauge) are on completely separate circuits. As the diagram shows, the PCM sensor gets it's ground from the PCM. The gauge sensor gets it's ground directly from the engine block. The sensor connector coming loose seems more likely than two completely different grounds failing at the exact same time.

If I helped you fix it, why not...

Your support is greatly appreciated
 

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Discussion Starter · #5 ·
Hello

Happy Thanksgiving!!

The ECTS does have three terminals but only the 1 and 3 pins are utilized. See Below


Font Rectangle Parallel Pattern Engineering




Product Rectangle Font Material property Parallel


Also I changed the correct sensor. See below
Font Parallel Rectangle Pattern Slope


One of the links you(pin cup) provided shows a second coolant sensor that I believe is meant to regulate HVAC blower fan when engine coolant has not reached operating temperature. I do not believe this sensor will have any bearing on the current issue at hand I'm picking up a ground signal on pin 1 and 5V on pin 3. It to my understanding that the 5V received at pin 3 sensor passes thru sensor and meets resistance(depending temp) and returns the lesser voltage to pin 33 of the ECM. I know I can not unplug the connector to test for voltage at pin 33.

I do not want to damage the ECM or its connector. Is it advisable to test for voltage at pin 33 on the ECM from the back of connector?
 

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This is when a Bi-Directional scan tool would come in really handy. The ability to watch and record data under driving conditions is priceless.

Thanks for the update.
-PC
 

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It to my understanding that the 5V received at pin 3 sensor passes thru sensor and meets resistance(depending temp) and returns the lesser voltage to pin 33 of the ECM.
That's not quite right. Pin 33 at the PCM is ground. There should always be 0V on that terminal. That doesn't change. It's the voltage on pin 7 of the PCM (pin 3 of the sensor) that will change. As the coolant heats up the resistance of the sensor reduces, which causes the signal voltage at pin 7 to reduce.

The ability to watch and record data under driving conditions is priceless.
Yes, but you don't need a Bi-Directional scan tool to do that. Any scan tool can read data from the PCM.
A Bi-Directional tool allows you to send data back into the PCM. But that's not a feature you would use to diagnose this fault.

If I helped you fix it, why not...

Your support is greatly appreciated
 

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A Bi-Directional tool allows you to send data back into the PCM. But that's not a feature you would use to diagnose this fault.
But if you're going to drop the money on a scan tool, it would be foolish to buy anything less.

The X-TOOL D7 is an incredibly powerful bi-dir scanner for under $400.
D7
https://www.amazon.com/XTOOL-Automotive-Diagnostic-Bi-Directional-Programming/

I have older projects in the shop at the moment (pre OBD1) so I really have no need yet.
If / when, either of our Hyundai's need deep scanned, this is the tool I'm buying. I have a pocket reader that only supplies codes.

-PC
 

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But if you're going to drop the money on a scan tool, it would be foolish to buy anything less.
I agree. But it sounds like Matt already has a scan tool of some description. I doubt he wants to out and buy a Bi-Directional tool if he doesn't need one.

If I helped you fix it, why not...

Your support is greatly appreciated
 
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