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Check that the thermostat isn't frozen closed.

Then check to make sure the purge line flows.

Make sure the water pump belt is intack, turning and not slipping

Make sure the coolant is at least 50% coolant to distilled water.  

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Check for codes.  What kind of sensor?

Did you change the Engine Coolant Temp sensor?

See my signiture to see how to check codes.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Ok, then, that isnt good.

Do you have a misfire?

What year car is this?

Are you saying it is not overhearing at all, but the instruments are falsely informing you that it is overheating?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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94 Eldorado no misfire no overheat at all you can unhook sensor and drive all day with no problem do you suppose the end that hooks to sensor is bad ? I'm stummped at this point. it's a really nice car with only 140000 miles on it 

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Ok, you have something going on, check the connector to see if its connectors are loose.    Did you have this before you changed the sensor?  You may have a bad connector, check the leads also for breaks 

P073 (E073) .....................................  Intermittent Coolant Sensor Signal

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Welcome to Caddyinfo.

I only recommend oem acdelco or remy sensors as others are prone to not being close enough to spec to work properly.

did you put teflon on the threads? If so they are not meant to have that

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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Did you have this problem before the sensor was changed?

You never know, as rock says, it could be a bad sensor.

Do you have an ohm meter?  If yes, I can give you the resistance spec, to check the sensor.  But don't assume its good.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Ok, I have company that is leaving.  Ill pull my 94 manual and give you the resistance.

Ill look at the wiring diagram and diagnostic tree for P073 and report back.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Regarding the connector, its possible the connector is bad, Ill look at the manual to see what it looks like.  The connector may have female connectors that may be loose or corroded, you may be able to remove the connectors from the plastic plug with a sharp pick and tighten the female connectors.  You can buy a new connector also.  

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Well you are getting an intermittant connection, sometimes its connected sometimes not.   Let me look at the manual, Im trying to get my mother in law the H out lol

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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I hope this helps, do you know how to get into the on board diagnostics to be able to monitor real time sensor data?

I believe you will get false readings, you will note that under "action taken" is NONE......, so there is no safety default of say 180 degrees or so.......having a bad ECT would be a critical failure condition potentially disguising a condition that could cause engine damage, so you will receive wacky temp readings by design that may set off alarms, etc.   By design, I believe it will keep trying to provide a temp as wrong as it might be.  The failure condition is the voltage changing 0.3 volts which equates to 11 degrees C or more in less than a second.  The intermittent code tells you that something is wrong.    We don't see a lot of ECT sensor problems.

This is just a guess, but something tells me that you are having a problem with your sensor. This sensor has a bit of complexity built into it because it has 2 ranges.    One of the worst types of problems you can diagnose is when you replace a part with a defective part, and proceed to tear your hair out because the problem still exists.   Start with checking the ECT sensor for resistance.  Keep in mind that it has two ranges, low and high.    Inspect the wiring in the area for damage and look for grounds, there is a ground in the area of the ECT sensor attached to the block make sure its attached solidly.

These diagnostic trees will help you navigate the problem.   I still need to get you the ECT sensor resistance range so you can test it.   Sorry for the delay, I have been hoppled badly with knee pain and have bad days.  Need surgery. 

 

DSCN0009.JPG

DSCN0011.JPG

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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I just looked through the manual and did not find any information on resistance.  That is surprising to me.   Ill look again, I recall in my 96 manual seeing a sheet of resistance specs for sensor testing.  I do have a 94 manual.  

I really like the 93 through 95 OBD1 cadillacs, the ability to get into the PCM parameters to monitor and override real time has always been intriguing to me.  Plus the PCM can be easily modified.   Cool stuff

Ill look again for the resistance specs.   But check the sensor, at room temp and at operating temp.  Can you get to the connectors with the sensor in place? 

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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With the attached information, you should be able to back probe the sensor using a digital voltmeter.  When cold you will have 5 volts with 0 volts when hot. I would connect my meter to the sensor return side or black wire according to that schematic above and the other lead to ground.   Watch the meter as the engine warms up, the voltage will drop, watch for erratic voltage swings as the engine gets up to operating temp.   The voltage should decrease steadily with no crazy behavior.

DSCN0013.JPG

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Thanks Logan, that's great.   I am sure its in the manual someplace, but have not found it yet.   thanks

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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