Toyota Corolla Trouble Code 22

Hello. I have a 1994 Toyota Corolla that is having some issues. Namely, it’s burning up coolant; I was driving to school the other morning and when I arrived and parked, I noticed large amounts of steam coming from under the hood; the coolant was boiling/steaming out through the overflow reservoir. I checked the radiator and the coolant level was low. I refilled it and it was fine for a few days and then the same thing happened, so I did some further investigation;

The check engine light was NOT on; but I checked for codes, anyway. This being an OBD1 system, I opened the hood and jumpered terminals T1 and TE1 in the diagnostic box and checked the dash; flash flash, pause, flash flash, long pause, repeat; a code 22, “Engine Coolant Temperature Sensor signal” (according to this site:

I bought a new temp sensor, installed it, and cleared the codes (by unplugging the battery). I refilled the coolant, drove it to and from school the next day, and rechecked for codes when I got home; nothing. I figured I’d fixed the problem. It was fine for a couple days. Then, today, on my way home, the coolant was boiling out again. I checked for codes; nothing.

So, I googled how to test the sensor with an ohmmeter; should be ~2000 ohms cold, and drop when heated up. I did this test on both the “new” and “old” sensors; the “new” sensor was ~2700 ohms cold (a bit high?), and dropped significantly when heated up. The “old” sensor was ~2000 ohms cold and also dropped when heated up. Both sensors appear to be good, yes? I put the “new” sensor back in and, again, checked the codes; code 22. That’s where I’m at right now. I’m thinking it may be the wiring/connector that plugs into the sensor that’s bad. I’m hoping someone here can give me some input :slight_smile:

Some other notes: at some point in all this, I noticed that the radiator fan was not coming on. I’ve read in a couple places, though, that they WON’T come on until the coolant reaches a certain temp (200F? 210?) It should’ve been on when the coolant was boiling, though, certainly? And it wasn’t. After I installed the “new” sensor, I meant to check and see if the fan was on when I got home (when the coolant would be hot enough to trigger the fan), but I didn’t remember until about 10-15 minutes after I’d parked, though; at that point I went out and turned the car on and the fan came on for a few seconds then shut off. I figured it was had cooled sufficiently while sitting and the fan had come on, sensed the cooled down temp, and shut off again. But today, after it boiled over again, I checked as soon as I got home and the fan was not on.

I can, however, get the fan to come on by turning the AC on, so the fan seems to be working to some degree (could still be a bad starter winding, maybe? I dunno).

Another note; about three weeks ago, the igniter in the distributor went bad and, in the process of tracking that down, I removed and replaced the entire distributor (including cap and rotor and also new spark plug cables) and, thus, had to adjust the timing and all that. The car runs fine, now; no hitching or missing and has good power and all. I don’t know if this could have something to do with the current issue or not, but, ya know, the timing of it… well…

Anyways, this is starting to turn into a novel, here, so I’ll post this now and await the influx of wise words! Thanks for reading! :slight_smile:

Oh, I forgot to mention: during all this, I’ve been watching the temperature gauge in the dash closely ever since the first incident with the steam. It only ever rose once; when I was on my way to AutoZone to get the new sensor; the coolant had boiled out and I only had a little left in the bottle in the trunk to put in. The temp needle jumped a little past middle, then went down to normal (a bit under midway), then jumped a bit, then down. Other than that one time, the temp gauge has been normal; starts cold in the morning then warms up to just below middle and stays there. Maybe this will be helpful info to someone :slight_smile:

You have 2 fans

The condenser fan will always come on with the AC

The radiator fan is supposed to come on at a preset temperature

How old is the thermostat?

I’ve noticed the two fans. There’s a big one on the inside/engine side of the radiator, and a smaller one on the opposite side. Upon further investigation, I’ve found that when I turn on the AC, both fans come on; the smaller/outside fan will stay on for, maybe, 20 seconds, then turn off. The bigger/inside (and louder) fan will stay on longer, maybe a minute, then also shut off.

As for the thermostat, I can’t say how old it is. I’ve never changed it and I don’t think my mother, who had the car before me, ever changed it, either. Suffice to say that it’s probably pretty old.

You just have a coolant leak you have to find. Low coolant causes overheating and the temp sensor can’t get a reading once the coolant level drops below it. That sets the code 22.

The first thing to do is get the cooling system full and get it pressure tested.

Could be a bad radiator cap. Replace it and the thermostat at the same time and filler up. Your main fan should come on when idling and the engine is warm. There is a relay and a switch to turn it on.

I concur with the radiator cap comment above. That’s the thing to do first. If the coolant isn’t holding pressure, the cooling system doesn’t work correctly and may steam. A faulty radiator cap can cause this.

Remember there are at least two engine coolant temp sensors which screw into the coolant jacket, maybe three if your engine has a separate cold start valve. Of the other two sensors, one is only for the gauge, the other is only used by the computer. So make sure the sensor you are checking is the correct one.

BTW, I don’t think the problem you are having is a temp sensor problem. Just b/c you get a code of 22, that doesn’t necessarily mean the sensor is faulty. It could mean the coolant at that spot is getting too hot, or not getting hot enough as expected.

The next thing to check is why the radiator fan isn’t coming on. I have a 92 Corolla, and on that version it has a coolant temp switch which also screws into the coolant jacket. It switches on and off at around 190 deg F. If that fails (which it did on my car) the radiator fan might not come on at 190 deg F like it should. I test mine by letting the car idle while watching the dash temp gauge. The fan comes on at about the 2/3 mark on the gauge.

And the next thing is to remove the thermostat, put it in a pot of water heating on the stove, and see if it opens and closes at the correct temperature.