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CE code 21.. Coolant Temperature Sensor or Circuit


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11 replies to this topic

#1 tidd1340

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Posted 14 April 2007 - 04:21 PM

I get 2 long and 1 hort led blinks..im gathering its the temp switch...rough idle at cold startup..Is the sensor a readily available part..car is an 89 GL EA82..thanks.

#2 Gloyale

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Posted 14 April 2007 - 06:09 PM

The code means that there is trouble in the circuit. it is not a diagnosis that the Temp Sensor(CTS) is bad. The Temp sensor is particulary prone to corrosion caused contact problems. Make sure that the connectors are clean and shiny.
You can test the CTS easily with an ohm meter. Measure resistance between the two terminals of the sensor. Cold, the resistance should be fairly high. around 2000-5000 ohms (2-5 kohms). Warmed up, the resistance should measure only 100-300 ohms. If it measures less than 100 ohms, zero, or infinte, it is bad.

#3 tidd1340

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Posted 14 April 2007 - 06:54 PM

Thanks..i havnt looked yet,but is the sensor in the radiator,or on the engine somewhere?

#4 Gloyale

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Posted 14 April 2007 - 07:06 PM

It's on the engine. On a SPFI(non-turbo) engine, it's very near the Thermostat cover, where the top radiator hose attaches to the engine. It's about the diameter of a quarter, with 2 wires coming off it. 4 inch leads to a black or green connector.

On a MPFI(turbo) engine it has is located on the back side of the intake under a bunch off crap. Turbo ones just have the wiring plug right into it, no leads attached.

There is also another temp sensor, but it has nothing to do with the ECU. It is the one that sends to the dash temp gauge. That one is smaller, with a single tab on it. It is only used for the gauge.

The electric switch mounted inside the radiator(pass. side, halfway up side of rad.) is for the electric cooling fan

#5 tidd1340

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Posted 14 April 2007 - 07:14 PM

Thanks..i appreciate the help!

#6 tidd1340

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Posted 15 April 2007 - 08:45 AM

Autozone says $98.00..tell me it isnt so....

#7 Gloyale

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Posted 15 April 2007 - 10:16 AM

Autozone says $98.00..tell me it isnt so....


Hve you tested it yet? Many many times there is a connection issue. Seems the ECU is vary sensitive to this sensor, and just a bit of corrosion or loosness can throw the code and cause running trouble, even overheating.

#8 tidd1340

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Posted 15 April 2007 - 01:36 PM

Just went out and cleaned it up..still got the CE light when i started the car. Do I have to clear the codes or will they clear themselves?

#9 Gloyale

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Posted 15 April 2007 - 03:27 PM

To clear the codes, Connect both the green "test" connector under hood and the white(or black) "read" connectors under dash. Turn the key to on(engine off) and depress accelerator pedal fully and then return it to halfway, hold it there for 2 seconds, then release. Start engine,warm it up and/or drive around the block. ECS light chould go off, stay off for 20-30 seconds, then blink. If it does, then all codes are cleared and none are present at that moment. Turn off and disconnect both sets of connectors.

If the ECS light does not go off, or goes out but then comes on and stays on then start over reading the new codes. Turn off car, unplug "test" connectors. turn the key to on with just the read connectors plugged in. That's read mode.

If you get a code there then run D-check mode. Connect only the Test connectors, then turn key to on(eng off) and do the full, half, off thing with the throttle. The Fuel pump will be cylcling and the ECS light blinking. Start engine, warm it up and drive a bit. ECS light should go off at first and then either blink if everything is fine, no code. If it comes on and stays on again there is a code. check the code. Is it the same as read mode? Repair, clear codes, and repeat as nescesary

#10 tidd1340

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Posted 15 April 2007 - 05:54 PM

Flashed,then went off. We will see in the morning when its cold if it throws a code again..thanks!

#11 PonchoCatalina

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Posted 15 April 2007 - 07:30 PM

Autozone says $98.00..tell me it isnt so....


Don't get too worried. My CTS went out about two weeks ago (confirmed with my handy multimeter). My local parts store quoted me $104, and it was special order only. I went to the only wrecking yard in town that has an EA82 Subaru and got the sensor for $5 ($5.40 with tax). Check your local yard, or see if anyone on the board has one for sale, if in fact yours is bad (versus a wiring issue).

#12 daeron

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Posted 15 April 2007 - 08:34 PM

before you go buying a new one, by ALL means please test it. The CTS should have a certain resistance when the engine is cold, and a different resistance when it has reached operating temperature. All you need is a multimeter to check it, and five minutes. these are often wiring problems, and NOT sensor issues... its a very common problem with fuel injected vehicles, responsible for many a check engine light.




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