Thread: Coolant Temperature Sensor

My car warms up all the way, I've replaced the sending unit for the dash gauge, it's working fine. Temps come all the way up, just idles super high and runs very rich.



This I know. My U13 ECU is equipped with a Calum Basic. I have adjusted the timing map to run the 9.5:1 CR, and I am indeed running a Bluebird MAF currently - though I have an N60 waiting to be installed in warmer weather. I would like to find a CTS designed for the BB, but don't even know where to begin to look besides asking GregV (I'll do that soon. Just have other priorities right now).

As far as having the correct sensor, since the difference in the B13 to B14 CTS was only the plug shape, I wonder if a Bluebird coolant temp sensor will match up to a B13 wire harness... also... the B13/14 sensors still took readings based off the same resistances. I wonder if the bluebird does as well or if it is different...

wow this seems like a very common issue! i will be making a trip to the Junk yard this weekend!

i think it maybe runnin a tad rich, but it doesnt have high idle or anything like that.. it just takes Forever for the idle to drop to normal and even then the temp needle never gets above that first white line..

ok, apparently a few things need clarification before this thread explodes any more.

Step 1: Check codes! If you don't have a code for your coolant temperature sensor, there are plenty of other things to check out. Many, many, many things can cause you to run rich, including the o2 being bad, leaky injector, stuck injector, false MAF readings, ecu being stuck in open loop mode, etc.

If you've got a code, replace the sensor. They cost about $10. If you have a spare for an SR20, test it and throw it in. Don't forget to erase the code. Your ECU will likely have 2 codes for the CTS that need erasing for it to run properly and take the CTS into account. Make sure to get both. If you don't, your ECU will simply continue to ignore the CTS.

B13 and B14 (91-98) sensors are identical in design and resistance. The only reason matching is suggested is because the plugs are different shapes. Thats it. The sensor itself is identical. So, if you're in the same position as me, where you are wiring directly rather than using the plastic connection clip that's usually on the harness, it doesn't matter if it was made for a 93 or a 97, it will work.

JDM vs. USDM is the only occasion where you might encounter discrepancies in the sensor type. Various other threads discuss this as well as other important differences between USDM and JDM.

The gauge on your dash does not get it's info from the coolant temperature sensor. There is a separate, 1-pin plug next to it that feeds it this information. The 1-pin plug goes directly to the dash cluster and does not assist in controlling the fuel mixture or behavior of the ECU. Only the Coolant Temp Sensor does this. If you're experiencing issues with your dash gauge, you're having a different problem that, again, could be a variety of causes not related to the CTS.

When making wiring connections, the wire type is not as important as continuity. What this means: soldering 2 different wire types together will still function so long as the solder is good and resistance is minimized. You may encounter soldering issues with specific types of wire. That information can be obtained in a variety of locations, even your local library. It's electrical engineering principles. The rule of thumb for soldering wire here is simply to make sure it's a good solder that actually connects the inner wiring of both wires together, and is not a "cold solder". If you don't know how to properly solder, learn.

The FSM is your best resource. It's even better considering it's free. If you choose not to listen to what it says, that's your choice, but it doesn't lie. Download it, print it, whatever it takes get it. Read it, and look through it for your problem. For the coolant temp sensor, there's even a procedure and data chart to test and verify your CTS is working properly. Do it. If it checks out, put it back in and move on to the next thing.

Nathan has a unique issue considering he's now running a bluebird ecu. Again, though, it's easy to see if a standard B13 or B14 CTS will work with the bluebird by comparing a standard FSMs resistances to those listed in the FSM for a bluebird vehicle.

If I come off harsh here, I apologize, but there is way too much baseless speculation and straight up bad information going on in this thread. Not to make it personal, but so far most everyone here is assuming it's the CTS without confirming that other issues don't exist or that they even have a trouble code for it. This is not hard to solve.

If you have doubts, or are convinced your CTS is bad, pull it out and test it like the FSM describes. It does not take long, and will give you a definitive answer. You can then continue troubleshooting and look to other possibilities.

To see of your ecus fan circut is working properly just use a paperclip and short out the two terminals for the coolant temp sensor and the fans should kick on, since it's telling the compnits like 900 degrees or something. I did this on my b14 and it kicked em on quick.

Sounds like your thermostat is stuck open...and the "tad rich" I'm sure is from the calum ecu you are running. He tends to put things on the safe side out of the box.



Excellent, excellent review. Thanks professor I think we can all pass the cts test now.

brand new oem thermostat from gregv.. that was the first thing i changed lol im going to wait till summer, if things dont change i will do further investigating.. also im gettin a nistune ecu Real soon

thanks.

Have Anyone Of You Guys Experiencing This Have Changed Your Alternator Within The Last Few Months Or So? If So Do U Remeber This Happening Before?

Reason I Say This Is Cause My Temp Went Almost To The Middle Today But When My Voltage Was At 13.7

When My Car Is @ 14.0-14.2 Volts Is When Temp Goes Nowhere Only Lil Past Bottom Needle...

Sorry About The Caps Again

IM GONNA TRY NEW NGK'S SEE IF THAT BURNS IT OUT

UPDATE!!

"So I took your advice Fazil. I looked at the dizzy plug and it was in rough shape for a long long time. I noticed a bare wire that was exposed after I accidentally crushed the clip when I was putting a tranny back on.

Took out my DVM and had the key to the on position. Tested the ignitor for juice and it was getting 11.6V. Then I decided to check the dizzy. On the harness side I got from one of the pins a 5.1V or so reading. I then tested it on the dizzy side and it was received about .1-.3! So looks like I need to source a dizzy. I did find the coil wire 12V wire broke from when I spliced in the MSD 8969 unit. Turns out my VVL solenoids also had a loose connection which I believe was the reason my car kept falling out of VVL at the track.

Long story short, turns out that my coil was getting a ****ty signal and not creating any or a good enough spark. I need to go through some parts of the harness and solder up some connections. I'm off to go pop some vvl." POSTED FROM VVL THREAD

now OUT OF ALL THE PEOPLE THIS IS HAPPENING TOO HOW MANY HAVE THE MSD8969 TAKING JUICE RIGHT FROM THE COIL?

my Summit switch is taking signal from the tach signal from ecu..