Engine Coolant Temperature Mismatch

[fendercare]

I have searched until I am blue in the face to no avail.  I have a 2001 24 valve with a Quadzilla Adrenaline tuner installed.  At engine operating temperature the coolant temperature sensor (located right next to the thermostat housing) is reading about 1,125 ohms of resistance which is about 190F.  This level of resistance matches the coolant temperature.  The problem is the ECT on the Quadzilla reads 160.  Disconnecting the two wire lead at the sensor seems only to affect the gauge on the dashboard and not what the Quadzilla is showing.  

 

Where is the ECM or PCM pulling the ECT of 160 from?  It does not appear to me it is from the sensor located at the thermostat housing.  Is there another coolant temperature sensor other than the one near the thermostat housing? 

 

Having the ECM think coolant temperature is 160 when it is actually 190 I think is affecting fuel consumption and maybe performance?

[AH64ID]

What is the dash showing? 
 

Sounds like the quad might not be looking at ECT. 

[Mopar1973Man]

ECT comes strictly from the ECM. PCM has nothing to do with it. Then the signal is sent out on the CCD network and then the cluster receives  the message for temperature and then the gauge displays it. 

 

Ohm values doesn't mean much. What I need is the Live Data tool and you to compare ECT and IAT values at a cold start up. Don't use the Quadzilla. I need the values from the CCD side not the CANBus side. This will show what value the CCD bus is transmitting. IAT and ECT should match at key on. They are the same type of sensor. 

[fendercare]

Many thanks for quick replies.  MoparMan I do not think I have the capability to read ECT and IAT.  I bought this truck used and it had the Quadzilla already on it.  You reference the Live Data Tool - what would you recommend for this year of truck?  I am familiar with EFI live as I use it frequently on a Duramax and 07 Cummins but as you know it is not compatible with 2001 Cummins.

[Mopar1973Man]

1 minute ago, fendercare said:

MoparMan I do not think I have the capability to read ECT and IAT. 

 

Any Live Data Tool that plug into the OBDII plug can.  Like I've had ScanGauge II and OBDLink LX both read it. Even my Innova Code read with live data will read it.

 

 https://www.scangauge.com/

 

http://www.obdlink.com/

[fendercare]

You are wealth of information and I greatly appreciate your help.  I want to make sure I understand the CCD and CANBus concepts.  My inference is input from ECT sensor is fed into the CANBus side of the ECM and the outputs of what the ECM is actually using as values is sent to the CCD side which is accessible/readable through the OBDII port?

[Mopar1973Man]

The Cummins ECM was designed with a CANBus communication. The Dodge Side was CCD Network. 

 

You can see the CCD side with the radio, central timer, etc. This is the bus that brings the temp data to the cluster. Which is also part of the CCD network too.

[fendercare]

Last question again checking my understanding.  Are the values of ECT or IAT or MAP read with a Live Scan Tool the values the ECM is operating with?

 

Thanks again and I will purchase a tool and investigate further.

 

 

[IBMobile]

                             YES, the ECM uses the same sensor inputs.

 

[fendercare]

Many thanks guys.

[AH64ID]

Maybe I missed it, but I don't see where you have said what the dash is reading. 

[fendercare]

Hi John,

 

You are correct I did not note this in the discussion thus far.  The gauge reading on the dash is slightly below 190F.  Interestingly I did replace the thermostat and seen the gauge reading drop slightly and the Quadzilla showed a 10 degree drop from 170 to 160.  My only concern in this matter is I want to make sure the ECM is receiving the correct coolant temperature.  In addition to what MoparMan has suggested I am going to call Quadzilla today to find out what light they can shed on the temperature mismatch and where their software is pulling the reading from.  My best guess at this point given the dash reading and sensor resistance I think the Quadzilla is in error but would like to confirm this.

[AH64ID]

What are you using to ensure the truck is up to operating temp?

[Mopar1973Man]

This why I want to verify the live data on a cold engine the IAT and ECT will match is the sensors are correct.