Code 61 in a 1990 GT

[BRP1979]

Borrowed a cheap scanner, pulled this code - ECT sensor. Went to the local autozone 5 minutes from my house and picked one up. Rplaced the sensor, cleared the code. I started the car and within 10 seconds the code SES light was back on.

Background on the car...

belongs to a good friend of mine. It was basically stock - x-pipe, flowmasters, BBK CAI. He overheated it bad and destroyed the engine. It sat about a year until I brought it over hear and began the rebuild.

Specs are:

91' 302 HO .040" over
GT40 heads mildly ported and o-ringed
Cobra 1.7 rockers
Cam is some mystery cam he brought me, it's .560" lift with the 1.7 rockers,
I measured it and did the math. PTV clearance is .175 E, .145 I
Cobra intake and 65mm TB
BBK 76mm MAF
30# injectors
BBK 255lph pump
BBK adj. FPR - set at 38psi
180* stat
BBK shorties, Summit x-pipe, 2 chambers w/ dumps
MSD billet distributor & blaster coil - timing 14*

The symptoms are - if I floor it, it breaks up bad and spits black smoke like diesel.

Should I try a BW sensor from Advanced? I read several reviews online that say they had problems with the AZ sensors. I am hoping it's not a problem with the wiring harness.


Any help would be greatly appreciated. I want to get this thing fixed so he can enjoy his car again. The Power Tour starts in a week, he has dreams of taking this car on the first few stops. I didn't make any promises, but am trying my best to oblige.

 

[BRP1979]

Also, it is a 5 speed car, and the ECM was recently remanned by Cardone.

 

[Mustang5L5]

Code 61 refers to ect coolant temp sensor fault or circuit grounded.

You can do a resistance check on the sensor to see if it's in spec, as well as inspect the wiring to make sure its not shorted to ground somewhere.

Post 2 has more info

http://www.stangnet.com/mustang-forums/636461-bad-ect-sensor-causing-problem-what.html

 

[BRP1979]

Sensor checks good, I swapped sensors with a local guy who has a 91' coupe. With my new sensor in his car - his car runs the same, no codes, etc.

The GT does the same crap with his sensor, SES light, etc. I am not good at tracking down wiring issues. I have zero patience for it. I think it's time for me to hand my friend his keys and let him deal with it at this point.

 

[jrichker]

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

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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