ECT Voltage Low

stock91

New Member
Apr 4, 2010
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Ok, here goes-
With my engine cold and koeo I get .63volts at pin7 lg/r wire at ecm-that is the ect wire-Its about 80* degrees out here, so somethings wrong. New ECT and new ECM. I bought the new ecm because someone who is very respected at another site said if I cut the lg/r wire at pin7 at the ecm and meaure the voltage it should be within temp range in the factory manual. So, I did this, and still got .63v, with the new ecm.
Any idea, why, with a new ecm, ect sensor I would be getting these very low voltage readings? Also, will this really impact the driveability of the car that much?
Thanks in advance
 
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Code 61 - Engine Coolant Temperature (ECT) sensor is or was too low. Failed sensor or bad wiring for the ECT.

Note that that if the outside air temp is below 50 degrees F that the test for the
ECT can be in error.


Check the resistance of the black/white wire to battery ground. If it is less than 1 ohm, it is good. If it is more than 1 ohm, the black/white wire has bad connections or a broken wire. Always take resistance measurements with the circuit powered off. Make sure that you do not touch the metal probe tips when you you’re your measurements. If you do, your readings will be off. Check the resistance of the Lt green/yellow wire at the sensor connector and Pin 7 on the computer. It should be less than 1 ohm. If it is more than 1 ohm, the Lt green/yellow wire has bad connections or a broken wire.

If those tests pass, remove the passenger side kick panel. Disconnect the computer connector and disconnect the sensor from the wiring connector. Measure the resistance between the Lt green/yellow wire at the sensor connector and ground. You should see 1 meg ohm or an infinite open circuit. Less than 1 meg ohm means you have some bad wiring, or the Lt green/yellow wire is shorted to ground.

The ECT sensor has absolutely nothing to do with the temperature gauge. They are
different animals. The ECT sensor is normally located it the RH front of the engine in
the water feed tubes for the heater.

The ACT & ECT have the same thermistor, so the table values are the same

ACT & ECT test data:

Use Pin 46 on the computer for ground for both ECT & ACT to get most accurate
readings.

Pin 7 on the computer - ECT signal in. at 176 degrees F it should be .80 volts

Voltages may be measured across the ECT/ACT by probing the connector from
the rear. A pair of safety pins may be helpful in doing this. Use care in doing it
so that you don't damage the wiring or connector.

50 degrees F = 3.52 v
68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61
212 degrees F = .47 v
230 degrees F = .36 v
248 degrees F = .28 v

Ohms measures at the computer with the computer disconnected, or at the sensor with the sensor disconnected.

50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms
212 degrees F = 2.07 K ohms
230 degrees F = 1.55 K ohms
248 degrees F = 1.18 k ohms

Diagram courtesy of Tmoss & Stang&2birds

88-91_5.0_EEC_Wiring_Diagram.gif


See the following website for some help from Tmoss (diagram designer) & Stang&2Birds
(website host) for help on 88-95 wiring Mustang FAQ - Wiring & Engine Info

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http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

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http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg