AyDee

is Ryeno right? because if this is the case them my O2 sensors are bad and not my ECT

over40driv

Im not a pro, but the ECU always has to know the engine temp. The O2 sensors tell the ECU how much fuel the engine needs.

Ryeno

iTrader: (3)

This is taken from http://engine.firebirdv6.com/

The RUN Mode has two CONDITIONS called Open Loop and Closed Loop. When the engine is first started and engine speed is above 725 RPM, the system is in Open Loop operation. In Open Loop the PCM ignores the signal from the Heated Oxygen Sensor (HO2S), and calculates the air/fuel ratio based on inputs from the TP, ECT, MAF sensors. The system remains in Open Loop until the following conditions are met:

1. The HO2S has a varying voltage output showing that it is hot enough to operate properly (this depends on temperature).
2. The ECT has reached a specific temperature (reported to be 170 degrees).
3. A specific amount of time has passed since starting the engine.

When these conditions are met, the system enters Closed Loop. In Closed Loop the PCM changes fuel injector on-time based on the signal from the HO2S. This allows the air/fuel ratio to stay very close to 14.7:1.

So basically its ECT sensor for a/f before operating temp and O2 sensor after.

AyDee

thanks - it makes sense

jdm93400

wow thats cool does anybody haVE THE PART NUMBER FOR AUTOZONE SENSOR

sc-driver

iTrader: (7)

yeah, i just confirmed it through the repair manual. The ecu uses the signal from the ect sensor to add fuel accordingly only when cold. i.e. open loop.

So that feel i got was when the car was still in open loop. Man it drove nicely though!

over40driv

I think we mean ETS engine temp. sensor.

BrunoMolly

I've been reading this entire thread and I know its needs to be bumped cause some information here is misleading... I am living proof that changing the ECT sensor helped me in my cars condition. ECT- Engine Coolant Temperature, not ETS- Engine Temp Sensor.
I read the Open loop closed loop post. True...But how would the ECM know if the engine was at the temp where is it supposed to switch over to "Closed Loop"? Gentlemen, It all points back to the Accuracy of that ECT sensor. These sensors can go Haywire when faulty and can send the wrong data when it feels like it. Even when cold it can tell the ECM that the engine is ready for Closed Loop when it's not....It can also tell the ECM that Its NEVER ready for closed loop, and let the system Time out??? maybe. But it all points back to what this thing is telling the ECM. I was getting power surging, power loss after Hot all day start stop traffic. Death by Pedal if I nailed the pedal on the highway.....On my Volvo 850 R, the engine Totally Died at 80mph on an 8 lane expressway!!! Try crossing that Frogger event with 4 way flashers, no power brakes, no power steering, and abrupt speed loss when kats trying to get home and not paying attention..It was my ECT on my Volvo that did this to me..
On my 93 LS400, Changed my ECT sensor with a new from Autozone Part# SU4007 $13.99 and the difference was like Night and Day!!!! Car runs like a Rocket now! No hesitation, no glitches in power, and the power is there at Command like Pow!! That theory if it ain't broke don't fix it should be kicked to the curb.. Especially if your car is over 12 years old MAXIMUM!!! Its a Sensor..they do go bad and quite often. Just think "Oh my car runs fine I don't need to change my sensors" and you take it on a trip and BAM!! Mechanics see you coming a mile away and Hit you hard with H I S diagnosis..
Case in point~ I have been chasing my issue since May. Drove to the Beach and the engine got Hot as H3LL when I was sitting Idling and not paying attention to the temp gauge. When I tried to drive off it felt like it was running on 2 cylinders...Since May I have changed all the typicals. NO FIX from any of them.... Just this past Saturday I changed the ECT and Problem solved!!! Made a 600 mile round trip without a single Glitch in 92 degree heat.
Bottom line, If you have owned your lexus since new, 90-98 or have bought a used one that is 10 years old or older, Even if your car runs like a dream now, One Day it won't..it'll be Hot, and you will be Pi$$ed. Keep you an ECT with you at all times so when that day comes, you will be ready. I can swear by this Fix...Best one I've seen yet. Fixed All my engine and performance issues. Those who are having Jerky acceleration, Death by Pedal, no power, or power loss...Start with the ECT sensor FIRST!! It's easy and less time consuming than almost anything else you can do. Wires, plugs, Dizzy caps and rotors take alot of time and if you have a bad or B|TCHy ECT you will be disappointed cause all that tune up stuff may have an initial impact of improvement but that ECT sensor will come back like a Cancer and haunt you. Sensor can fail in various ways from Hard failure to marginal to intermittent...I am living proof of that...
Sorry for the Rant..but its Proven!! It you see no change in performance after you change yours then yours was probably still good, but its days were still numbered.... A New ECT resets the LIFE meter of performance even though you don't notice it right away, your days are numbered if you don't change it!
~Bruno Molly
P.S. I am from the land of Troubleshooting "In the Hood" of Industrial Automation, PID Instrumentation, PLC's, Lasers and Motion sensors so don't tell me about Sensors! I wouldn't bet money on ANY sensor right off it's assembly line... so there. You can never own enough of them. I have 3 spares of every sensor on the 1UZ from CPS, to TPS... Cause I know the aliens are coming..!

expansive

this thread is truly a gem! very invaluable information here and everyone who posted was very useful and gave their experiences. I never would have thought of the ECT sensor but i did think about flushing the Coolant at some point.

Seems like a reasonable DIY type of repair and cheap too.

lexusB3

iTrader: (1)

just got mine thanks to this thread hahhaa..going to put it in when i get my radiator

KA8

iTrader: (1)

I think coolant sensor is the culprit for my engine. At operating temp my car would not move even at wot. At first I thought maybe
it was fuel pump because fuel was low but not empty. Then yesterday it happened again with just under half tank of gas. This morning it ran fine again. I'll give this a shot today.

dannysc400

[QUOTE= I havent taken the old one out yet to see how the fact. sealed it. Good catch on needing a deep well socket, as I keep some tools at a diff. location 19mm... The part # was a wt653z the invoice refers to the part as a radiator switch, but of course I told the guy i wanted a coolant temp. sensor. [/QUOTE]

i also got that temp sensor(wt653z) and it doesn't work for a 92 sc400. the correct number is TFS638 and it's 97.99 at advance auto, special order. I'm gonna check online and see if i can find it for less. Funny thing, mine isn't bad, i tested it, but thought for 20 or 30 bucks, might as well get a new one. Not feeling that way anymore, not for 100.00
Oh, and the sensor i'm talking about is at the bottom of the radiator.

over40driv

I posted that part # for a 95 SC400. The ECT is at the front of the block.

blacksc4

iTrader: (1)

i just finished changing mine, and had my battery unplugged the entire time i was doing it (bout 2 hours, had to leave the garage for a while) anyway when i finished, my car seems to idle weird, and not only idle weird,, but my temp gauge went up faster than normal and stays at about midway, i just finished about 5 mins ago and havnt driven the car yet, just started and idle, seems very off now, everything went back how i took it off, no CEL, and no leaking coolant frm the sensor (it leaked alot when i removed the old one) i did refill the coolant though
anyone have any ideas? its an autozone piece $22

louie1951

iTrader: (1)

all posts regarding sensor change point towards sensor in center of engine, but toyota reported sensor which the ECU reads is on the radiator, and sometimes called the radiator switch. i changed this one, around 85 dollars from dealer because discount auto-parts didn't have one.

gone is occasional ruff idle, loss of power, and mileage was down to 19mpg from 23.

i think the sensor in the center is a temp gauge but goes to the cluster?

i would not think SC and LS would be different in design for the engine.

no where have i read about the sensor on the radiator.

also there is an ECT and an ETS.

running great again, 1992 SC 400 w/ 176k.

also took the 30 amp fuse out to re-set ECU