What exactly does this code mean?
Thread Starter
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Mountain Pass
Joined: May 2004
Posts: 201
Likes: 1
From: El Paso, TX
What exactly does this code mean?
I just did the KOEO test on my 89 f150 4.9l and I got code 51. According to the book this means " ECT sensor open". Does this mean I should replace this sensor and if so where is it located or what does it look like? I really appreciate all of the help you guys provide. This stupid problem has been boggling my mind for weeks. This forum has got to be the greatest resource there is.
Senior User
Joined: Feb 2004
Posts: 315
Likes: 2
From: Miami
There are two engine coolant sensors.
One is tha small sender that feeds the Temp guage. Is has only on wire and on a 5.0/5.8 is located on the top of the intake manifold towards the front drivers side.
The ECT is the Temp Switch that tells the computer when the engine has warmed up and can start using info from the O2 Sensor to mix the fuel. If this sensor is bad, the truck will run in Open loop (Preprogrammed fuel settings rather than adjusting the mixture based on how the engine is really running.
I'm not 100% sure about a 4.9, but on a 5.0 and 5.8, The ECT swich that code 51 reffers to is located right under the Throttle body. It has a three wire connector on it and screws onto a fitting that has connections for the heater hose and Throttle body coolant lines.
http://www.kemparts.com/TechTalk/tt13.asp
Before replacing it, Unplug it and clean the contacts with WD40 or some other contact cleaner. Then plug it back in securely and test again. Sometimes they just develop a bad contact on the connector.
One is tha small sender that feeds the Temp guage. Is has only on wire and on a 5.0/5.8 is located on the top of the intake manifold towards the front drivers side.
The ECT is the Temp Switch that tells the computer when the engine has warmed up and can start using info from the O2 Sensor to mix the fuel. If this sensor is bad, the truck will run in Open loop (Preprogrammed fuel settings rather than adjusting the mixture based on how the engine is really running.
I'm not 100% sure about a 4.9, but on a 5.0 and 5.8, The ECT swich that code 51 reffers to is located right under the Throttle body. It has a three wire connector on it and screws onto a fitting that has connections for the heater hose and Throttle body coolant lines.
http://www.kemparts.com/TechTalk/tt13.asp
Before replacing it, Unplug it and clean the contacts with WD40 or some other contact cleaner. Then plug it back in securely and test again. Sometimes they just develop a bad contact on the connector.
Lead Driver
Joined: Nov 2002
Posts: 9,557
Likes: 44
From: Concord, NC
I would double check the wiring to the sensor, and test the sensor itself before condemning it as a bad unit. A Haynes manual lists the resistance values and corresponding temperatures for the ECT (it's not a switch). Make sure you have a good connection at the sensor as well - since there is very little current running through the wires, any change in resistance can create a big difference in the voltage the computer sees.
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Mountain Pass
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From: El Paso, TX
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Thread Starter
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Mountain Pass
Joined: May 2004
Posts: 201
Likes: 1
From: El Paso, TX
Well, this morning I went and removed the sensor and cleaned it. I also re-routed the electrical connector as it was a little snug. Now I don't get the code 51 any more and my idle has dropped from 1000 down to between 750 and 800. Thank you all for your help.
