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2.9L Coolant Temperature for ECU

ab_slack

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Am I correct that the Coolant Temperature Sensor used by the ECU is different than the one used for the dash temperature gauge?

If so, where is the one used for the ECU located?

Thanks.
 


RonD

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Dash board temp gauge uses a 1-wire Sender
ECU(computer) uses a 2-wire Sensor called the ECT(engine coolant temp) sensor.

They are usually located near the thermostat housing right next to each other.
On the 2.9l they should be just under the throttle body(where the big air filter pipe hooks up to the upper intake).

ECT sensors and temp senders are easy to test, use an OHM meter on cold engine, resistance should be high, above 20,000 ohms
At operating temp, 210degF, should show about 2,000 ohms
 
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ab_slack

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I'll run the test tomorrow if I can find it. Just checking off things.

Thanks.
 

ab_slack

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What a PITA to get at...well for a simple measurement it is hard to get probes on the sensor.

The plastic housing on the plug was broken on half the sensor. Probably would have made sense to change it given that when I changed the thermostat a week ago.

41K cold (70F outside) and 2.78K hot. Does that sound in the ball park? Dash gauge was just under half scale which is as high as it was going to get while idling.

KOEO test did not generate a code when engine warmed up so I am guessing it can't be too far out.
 

ab_slack

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Found a table it says 41K should have been about 65 deg, it did get cooler overnight so seems right on. Now sure how hot was hot, but 2.78K according to my table is 195 deg which sounds suspiciously close to what I heard for thermostat temperature. I would not have expected it to be that close.
 

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Those numbers are fine.

1/2 on most Ford temp gauges is 225degF, so normal warmed up needle would be 1/3 to 1/2

Yes, t-stat should be a 192 or 195degF model, engine operating temp of 200degF to 230degF will give best MPG and best lubrication.

Running an engine "cooler" sounds good but actually isn't, oil doesn't get hot enough to "burn off" water(condensation) and fuel contaminants(blow-by), and engine will run richer(lower MPG) which causes higher wear on spark plugs, O2 sensors and Cat converters.
 
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