replace ACT sensor and coolant temp sensor if not broken?

[bloopbloob]

like the title says. if i dont have codes or any reason to suspect the ACT sensor or coolant temp sensor are bad, is there any reason for me to replace them? only reason i ask is because i just remembered i have new ones laying around somewhere. or is this just a case of if it aint broke, don't try to fix it? thx

 

[squeak93]

Ain't broke, don't fix it. I did this with my egr sensor in a prev car, it wouldn't start for 3 days after. No reason, just didn't start. Sensor wasn't bad, even put the old one in, but no fire. Real weird.

 

[HISSIN50]

The sensors can be within absolute spec (no code) but out of calibration. I would test them at a couple of temps to see how close to being within calibration they are.



Good luck.

 

[jrichker]

Dumping the codes will normally show a faulty sensor. The ACT & ECT may be on the outer limits and not set a code but cause problems. Use a DVM or multimeter to check them.

Pin 25 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.

Pin 7 ECT signal in. at 176 degrees F it should be .80 volts

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

Here's the table: The values are +/- 15%, so don't get worried if your readings vary a little bit.

Voltages are measured across the two connector pins of the sensor with the sensor connected. Some safety pins used to probe the connector from the rear will be helpful

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