Engine coolant hot

ALEX K

MEMBER
1997 CADILLAC DEVILLE
160,000 MILES

Hi guys! Thank you for possibility to ask you question.
Could you please give a hint? In my car a have a problem, it's show engine coolant hot and idle engine with code P1258. Then it was disappear, then again I had this code and sigh on dashboard then disappear. During this problem I was checking real coolant temperature and it was normal. I cannot figure out what I should check or replace. Five days ago I had a problem with cylinder and changed one spark plug by misfire cause. Now is no code and no problem but when I'm driving it can appear. Coolant level is okay.
Thank you for your advise and help.
Alex

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,645 POSTS

Hi,

If the you are sure the engine is no overheating and the coolant level is full and clean, I would suspect the engine coolant temperature sensor is bad. This sensor is used by the computer to determine many things.

The Engine Coolant Temperature (ECT) Sensor is located on the Left hand rear corner of the engine, below the exhaust gas re-circulation valve. If you look at pic 1, it shows the sensor.

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Here are the directions for replacement. The remaining pics correlate with the directions. This is where I would start.

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1997 Cadillac DeVille V8-4.6L VIN Y
Engine Coolant Temperature (ECT) Sensor
Vehicle Powertrain Management Sensors and Switches - Powertrain Management Sensors and Switches - Computers and Control Systems Coolant Temperature Sensor/Switch (For Computer) Service and Repair Procedures Engine Coolant Temperature (ECT) Sensor
ENGINE COOLANT TEMPERATURE (ECT) SENSOR

pic 2

ECT SENSOR REPLACEMENT PROCEDURE

Notice:
Allow sufficient time for the engine to cool before removing the Engine Coolant Temperature (ECT) sensor. Excessive coolant loss or personal injury may result if the engine is hot.
Use care when handling the coolant sensor. Damage to the coolant sensor will affect the operation of the fuel control system.

Removal Procedure
1. Partially drain the coolant system.

2. Disconnect the ECT sensor connector.

3. Remove the ECT sensor.

Installation Procedure

Notice: A non-hardening sealer should be applied to the sensor threads prior to installation to prevent coolant leaks. Use P/N 1050805 or equivalent

1. Install the ECT sensor. Tighten the ECT sensor to 20 Nm (15 lb ft).

2. Connect the ECT sensor connector.

3. Refill the coolant system.

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Let me know if this helps.

Joe

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