Cooling Fans Continuously Run On Ae93 7afe

[rob83ke70]

Just wondering if someone can shed some light on this...

 

Is there a separate ECT sensor for the engine ECU and another one for the temp gauge? My cooling fans keep running but my temperature gauge is reading less than normal operating temperature, and the engine isn't warming up fully, and the idle speed is staying up around 1000rpm or so.

 

I suspect a faulty ECT sensor....

 

Robert.

[Sam_Q]

I will have to have a look on my 7afe engine to see if it does have a sepearate sensor like the 4age engines. The fan will also stay on if the engine is in fault mode...

[trd]

the fan will switch on if the sensor or the wire to the sensor is broken, easy to check - if you ground that sensor wire, the fan should turn off (i think it sits on top of the themostat housing - single wire)

[rob83ke70]

no MIL so it shouldn't theoretically logged any faults.... Will find and check wire in the mean time. I forgot to bring my multimeter home tonight :rolls:

 

Robert.

[rob83ke70]

took it for a squirt..... MIL illuminated after driving for a little bit. There are three possible ECT sensors as well, a single wire on the thermostat housing, a twin wire on the thermostat housing and a single wire on the pipe at the back of the water pump. Disconnecting and/or playing with wires at ECT sensors on the thermostat housing make no difference.

 

Repco autotech seemed to think that the twin wire sensor at the thermostat housing was the ECT sensor and it was an NTC thermistor so theoretically open circuit would be cold and closed circuit would be max temperature, assuming there isn't a self diagnostic facility built into the ECM software....

 

I'm getting the exhaust pipe hooked up early this week (its a little loud with just extractors lol) and then I'll run it into work and hook our generic scan tool up and fault read it.... if that doesn't make any sense then I'll borrow a toyota scan tool from the toyota dealership next door and fault read it!

 

on the plus side, no rattling noises from the engine or clouds of blue smoke any more :D

 

Robert.

[Raven]

Tridon Online Parts Catalogue

 

I'm an automotive parts interpreter by trade.

 

If you're wanting to know what sensor/sender is what, click the above link, enter in all your car details and hit search.

 

Once its loaded up, click on the corresponding part number and it will show you a picture of what is what.

 

You should be able to work out which one it is.

 

Personally I think its the thermo fan switch earthing itself out, causing your fans to be on all the time as the water temp sender would only cause the car to run rich or lean, depending on the failure.

 

The reason I think that it is the thermo fan switch is because my 5K was doing the same thing, until I swapped out the thermo fan switch with a new one from Tridon and all problems are now fixed. :D

 

Hope this helps!

Edited May 23, 2010 by Raven

[altezzaclub]

Bring it down to the washing machine repair shop! :D

 

I fix everything from washing machines, dryers, coffee machines, floor polishing machines, vacs, microwaves, treadmills and stacks of other things I knew absolutely bugger-all about a year ago!!

 

I've found it all runs just like the automotive trade... take a guess and replace something, if that doesn't solve the problem, replace something else until the problem goes away or the customer can't afford any more! :(

Edited May 23, 2010 by altezzaclub

[rob83ke70]

lol the focus of my job (as an automotive technician) is to make the right diagnosis, replace the faulty parts, and have the customer concern solved first time..... I think holden's phrase is "fix it right the first time" using what they call "strategy based diagnostics"

 

I've seen plenty of people in the automotive trade throw parts at something until it goes away (or the customer takes it away) lol.... the thing that really takes the cake, tops it all off is when I was working at my last job, we had a v6 commodore come in with a MIL illuminated, the boss says "the check engine light is on, you're going to have to fault read it and see what code is in it. It has been here twice before with a TPS related code, if it has the same code logged then you are going to have to replace the TPS again as it is obviously another faulty part.... we'll try a different supplier (aftermarket) of TPS which should fix the problem"

 

A car logs a DTC and turns the MIL on.... you fault read it, replace a component without testing it, it comes back shortly after with the SAME DTC, so you replace the SAME component again, it comes back shortly after with the SAME DTC.... at what point do you say "This hasn't fixed the problem so therefore there must be something else wrong with it" ??

 

They wouldn't have listened to me at that stage in that job so I fault read it, it had the same code logged, so I replaced the TPS again, test drove it, I thought there was something not right with it as well, but the MIL did not re illuminate, so we gave it back to the customer, and they rang up the next day to say the MIL was now on again.....

 

Intelligent lol O_o

 

I think I'll fault read it with a scan tool and see where I go from there!!

 

 

Robert.

[Raven]

This is why the technicians of today's trade rely too much on computers and not enough about the inner workings of the electrics or engine to know what does what.

 

Say the words carburettor or tappets and they'll run the other way with their tail tucked between their legs!

[rob83ke70]

hey, I do old stuff too!!

[Raven]

Haha, that wasnt directed at you dude. You're a year younger than me, so I suspect you would've grown up with carburettors and tappets ;)

 

The issue is the younger generation. All about technology these days.

 

Not everything can be solved by plugging a car into a scan tool.

Edited May 24, 2010 by Raven

[rob83ke70]

fault read vehicle using a generic scan tool to find the following codes:

 

coolant temperature signal

engine knock sensor signal

 

the fans run all the time with the key on, and the MIL illuminates after you start to drive the vehicle.

 

The knock sensor is faulty (physical damage) and is not manufactured by an aftermarket supplier, TGP is $195 trade.... I've ordered the part.

 

There appears to be three coolant temp sensors installed and connected on this vehicle, one at the back of the water pump (single wire), and another single wire sensor and a twin wire sensor on the thermostat housing near the gearbox. In the data list on the scan tool it displayed a seemingly correct engine coolant temperature parameter..... this is getting confusing. I'm guessing I have a problem with the sensor that the ECU uses, which is separate to the sensor for the gauge. If this is the case, why does the scan tool use the signal from the gauge in the data list?

 

Can anyone shed some light on what sensor does what and why there are three of them?

 

I've attempted to clear codes, the scan tool said to disconnect the battery for a minute, repco autotech said to disconnect the EFI relay for 30 seconds - I've tried both, and nothing has changed and the same codes are logged. I'm also getting atrocious fuel economy which would make sense too.

 

I think I need a genuine toyota workshop manual which hopefully has a diagnostic procedure for "cooling fans continuously run with key on" and some good identification information as to what sensor goes with what...

 

I might need to clear the codes with a toyota scan tool as well - I had this problem with an ultrascan scan tool on a mitsubishi UG nimbus - it wouldn't clear the codes and the vehicle remained in a limp mode - caused no end of problems sorting it out!!

 

Robert.

[Raven]

One would think that if its was the ECM sensor then the computer would be reading it as being cold all the time, causing it to run rich.

 

But that doesn't explain why the fans are running constantly.

 

Fan's running constantly is usually a rooted TFS earthing out regardless of the temperature.

 

The knock sensor would just retard the timing in case of detonation, but, if its getting excess fuel, it could also be triggering the knock sensor to throw a code as it wouldn't be getting the correct reading with the excess fuel being pumped into the motor (if that's the case).

 

All we can do is speculate, so my guess is its a combination of the ECM, TFS, Knock and Oxygen sensors being on their way out.

[rob83ke70]

fans running on:

two things control the circuit for the fan relay, the water temp switch, which is a single wire sensor on the thermostat housing, and the ac pressure switch. I have a wiring diagram and workshop manual that toyota kindly lent me so I will get to the bottom of that tonight.

 

ECT fault code:

the coolant temp sensor for the ECU is the two wire NTC thermistor located on the thermostat housing. Again, I have wiring diagram and workshop manual so I will follow that up tonight as well.

 

Knock sensor code:

The sensor is physically busted. Part arrives tomorrow from Toyota.

 

this would be a NIGHTMARE if I was still at ultratune trying to get to the bottom of this!!!

 

Robert.

[rob83ke70]

not having a body electrical systems manual in front of me this is just speculation, but I'd say the third temperature sensor near the water pump is for the gauge.

 

Robert.