vristang said:I don't see any way for the ECT to make noise. It's just a thermistor.
After reading all of your threads, I would have to say it is time for a new water pump.
It would be nice to inspect the pump before forking over the cash.
I just don't know how you would inspect it.
jason
A bad ECT will set a code 21 or 54. Engines with faulty ECT's may have hot starting problems because too much fuel is supplied during cranking.
Code 21 – ECT sensor out of range. Broken or damaged wiring, bad ECT sensor. Note that that if the outside air temp is below 50 degrees F that the test for the ECT can be in error.
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
Pin 25 on the computer - ACT signal in. at 50 degrees F it should be 3.5 volts. It is a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower intake manifold, the voltage readings will be lower because of the heat transfer.
Voltages may be measured across the ECT/ACT by probing the connector from the rear. Use care in doing it so that you don't damage the wiring or connector.
Here's the table :
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
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.
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
Hey Jrichker,
I have eliminated half my codes, on to 21. Got the code and the car does have symptoms indicative of the sensor or wiring being faulty. I just want to do the test first thou for learning purposes and because if it is a wire, I can save the $80!
1) What is the deal with the degrees? How am I supposed to know what temperature the sensor is?
2) You said voltages can be tested by probing the ECT/ACT sensors. Do you mean that for each one you can simply put a lead of your dmm on each of the wires coming out the clip? I did this on the ECT using safety pins and the voltages were 0. Does this mean my sensor is fried?
Thanks as usual for your help!
Wait Til the car is cold. Then just look at your outdoor temp. If it's 80 degrees, then look at the resistance values for 80 or as close to whatever temp you are at.
For the ect, you are measuring resistance. Unplug the plug and measure resistance on sensor across the two plugs.
Sensors are cheap. Rockauto has a number (including motor raft) for about $20
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No. Unplug the sensor and ignore the wiring you just removed.
Prob both pins in the sensor itself. You are measuring resistance through the sensor.
Just to take a step back. Are you running the codes with the engine all warmed up? If you run the codes with a cold engine, you will always get a code 21. Need to do it on a hot engine.
i know this is an older thread but if If the sensor is bad should I get a code at all?If your digital meter was set on resistance in Ohms, and you got 0 across the two leads on the sensor, that means it's open and bad and should be replaced.
What I would do first is erase the codes, go for a drive, and rerun them. If code 21 is back, then I'd replace it.
ok not getting any code but noticed yesterday the fan jumped right on when I started it and it's never done that before. I had the car to the tuner for a retune the last part of Jan. and he said something to the effect of the car when warmed up it was still showing as reading only I think 1 hundred and something degrees but I'm sure my aftermarket guage was reading correct as it always does read correct; I'm sure he was talking about on his laptop and in the parameters I guess.The ECU will throw a code if the sensor values are outside of an expected range.
It should throw a code if bad
stock tuned ECU and not necessarily difficult starting on hot days it just does what it does when I go to take off. It's almost like once I release the clutch and if I haven't given it enough gas pedal or keep playing with the pedal while waiting for traffic to clear, it will die but will start back up. Once I take off I'm good I can stop at a light and it be fine.Is this an aftermarket ECU or a tuned stock ECU?
I only ask because you say the fan came on when you started the car, but the stock ECU doesn't have the means to control a fan so what is controlling it then?
Difficultly starting on hot days is a sign of being rich, and one of the causes of that is incorrect readings by the ECT, but again, is this a stock tuned ECU or something else?
i also tried another used CCRM that I had lying around actually likely the one that came off the stock 94 Cobra setup ( currently in the car is my 95 modded tuned setup out of my wrecked 95). I also have another 95 302 and will try that CCRM when I get home. The one I tried yesterday did not yield a different result with fan coming on when I start the car.Is this an aftermarket ECU or a tuned stock ECU?
I only ask because you say the fan came on when you started the car, but the stock ECU doesn't have the means to control a fan so what is controlling it then?
Difficultly starting on hot days is a sign of being rich, and one of the causes of that is incorrect readings by the ECT, but again, is this a stock tuned ECU or something else?
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