ECT wiring ?

[rwood126]

I've been having some issues with my 89 vert...so I pulled the codes. I came up ECT low voltage and BPS low. So I got a new ECT form Motorcraft and it has been updated. New sensor is different and comes with a pig tail plug. The problem is...the pig tail has 2 white wires ...and the instruction doesn't tell what color to connect the wires to. Does it matter ?

Thanks

 

[Five_Oh]

Not sure what you got but I just purchased a new ECT about a month ago from napa and it was plug and play (no pigtail needed). But if both wires are white then it shouldnt matter which one goes where.

 

[jrichker]

BPS - did you mean TPS? What were the specific codes you got?


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.[/b]

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 - Engine Information

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

Fuel, alternator, A/C and ignition wiring
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

 

[rwood126]

BPS - did you mean TPS? What were the specific codes you got?

No not TPS ...barometric pressure sensor.
From a actron code scanner code 61 & 22.

I've been having a on going sputtering issue. But it's only over 3k rpms...and it's not doing all the time.

I started with the basics first...Plugs, Cap, Rotor, wires.
All Motorcraft parts and 9mm Ford Racing wires.
Then someone told me it was probably the ignition module. So I change it and put in a new (rebuit distributor) ...and a new MAF sensor.

The car just passed emisson test with great #'s.

It's just really anoying

 

[jrichker]

Code 22 or 126 MAP (vacuum) or BARO signal out of range. The MAP or BARO sensor is pretty much the same sensor for both Mass Air & Speed Density cars. The main difference is where it is connected. Mass Air cars vent it to the atmosphere, while Speed Density cars connect it to the intake manifold vacuum. Its purpose is to help set a baseline for the air/fuel mixture by sensing changes in barometric pressure. The MAP or BAP sensor puts out a 5 volt square wave that changes frequency with variations in atmospheric pressure. The base is 154 HZ at 29.92" of mercury - dry sunny day at sea level, about 68-72 degrees. You need an oscilloscope or frequency meter to measure it. There a very few DVM with a price tag under $40 that will measure frequency, but there are some out there.

The MAP/BARO sensor is mounted on the firewall behind the upper manifold on 86-93 Mustangs.

Baro or MAP test using frequency meter - run the test key on engine off. The noise from the ignition system will likely upset the frequency meter. I used a 10 x oscilloscope probe connected from the frequency meter to the MAP/BAP to reduce the jitter in the meter's readout.

If it is defective, your air/fuel ratio will be off and the car’s performance & emissions will suffer

Some basic checks you can make to be sure that the sensor is getting power & ground:
Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter.
Check the resistance between the black/white wire on the MAP/BARO sensor and then the black/white wire on the EGR and the same wire on the TPS. It should be less than 1 ohm. Next check the resistance between the black/white wire and the negative battery cable. It should be less than 1.5 ohm.

The following power on check requires you to turn the ignition switch to the Run position.
Use a DVM to check for 5 volts on the orange/white wire. If it is missing, look for +5 volts at the orange/white wire on the TPS or EGR sensors. Use the black/white wire for the ground for the DVM.

 

[rwood126]

Thanks...