water temp sensor

[Tim Catton]

I have a '94 Legacy wagon, auto, w/ 220+K on it. I had been getting intermittent CEL, codes 21, 32, 35. I replaced the canister purge solenoid, cleared the codes, and now I'm just getting an intermittent 21. The CEL light comes on for about 10-20 seconds while the temp gauge is in mid-travel between cold and operating temp, then goes out and stays out. Temp gauge on the dash appears to be functioning normally. Does this sound like a "typical" sensor failure or might there be something else at work here? Anything I should be aware of if I need to replace this?

Thanks.

[Legacy777]

The gauge on the dash and the ECU use two different temp sensors.

How does the car run when cold?

The sensors are pretty cheap, around $20, so I'd suggest replacing it.

[Tim Catton]

The car runs fine when cold. If I just let it sit and warm up for awhile (I usually don't, but lately I have while I scrape the windows, I live in northern MN) idle speed fluctuates a bit, sometimes jumping to 2,000 RPM).

[codfizzle]

I just replaced the coolant temp sensor on mine, also. I was surprised to discover that a 3/4" deep socket fit even more snugly on the sensor than any metric size. Also I had to temporarily disconnect the PCV hose so I could get at the sensor at the proper angle. Easy job, though.

[Tim Catton]

Thanks for the reply, I just picked one up. Did you have to drain any coolant, or did you lose much when you pulled the old one?

[codfizzle]

I just plugged the hole with my finger as I pulled the old one out and put the new one in. Probably only lost 5 drops of coolant. It's completely unneccesary to actually drain any coolant out, as the manuals usually say to do. And make sure the socket you use is a deep one, so it can fit over the electrical connector. And a 6" or 8" extension helps a lot. But, seriously, I changed mine in 5 minutes while on a cigarette break at work. Easy peasy lemon squeezy.

[Tim Catton]

Thanks, good to know since I don't have a garage and it just warmed up to -1. Was yours doing the same? Intermittent Check Engine Light during warm up, error code 21?

[codfizzle]

Actually I was having a totally different problem, but I initially thought the coolant temp sensor was the culprit, so I changed it. It turned out to be something else, but I'm glad I changed the sensor anyway because when I took mine out, it fell apart in my hand; the plastic part where the electrical connector connects to it just fell off of the metal part. It was really corroded, but it never did throw a CEL. But changing it fixed a couple of little electrical quirks I was questioning previously, so it helped there too.