Hi team,
looking for some basic suggestions on an issue that has just started on my 2002 Honda Fit. When I start the car the blue light comes on the dash to inform me that the engine is currently cold, this turns off after about 2 minutes driving, which is perfectly normal. However, after a further 30 minutes driving the blue light comes back on solid and obviously convinces the ECU that the engine us cold, when it is quite clearly not (blows very hot air through heater) this leads to an increased tick over, around 1500 rpm, due to the engine thinking it is cold, despite that not being the case.
Has anyone had similar experience of this issue ? If so, what remedied the problem? And..where is the water temperature sensor located?
thanks in advance.

 

Hi from a fellow Kiwi. I haven't had that problem, but a good test would be to use an OBD adapter and monitor the reported coolant temperature directly, to see if the readings look plausible (I use a Jaycar OBD dongle and the Torque app on my Android phone). It could be that the thermostat isn't working properly, or that the radiator fan(s) are running when they shouldn't, perhaps due to a stuck relay or a faulty radiator fan thermoswitch.

Just after starting, try turning the AC on and check that both fans turn on, and that they turn off again when you turn the AC off.

The coolant temperature sensor is at the back of the engine, just above the hoses going to the cabin heater core. There's also a thermoswitch that cycles the radiator fan, which is mounted in the thermostat housing, just next to the upper radiator hose.

Let us know how you go...

 

A thought: even though it's winter, you might be using the AC to help demist windows. That will force the radiator and condenser fans to run which might overcool your coolant, especially if you're also using lots of cabin heat.

 

Thanks for the suggestions, I’ll look into those this weekend.

I have been using the AC to demist the windows on a hot setting.

cheers Al

 

Interesting. No doubt that's a great way to defog the windows in winter, but maybe combined with the cooling airflow while driving it's enough to overcool the engine coolant, especially if the thermostat isn't closing properly. It would be good to rule out the ECT sensor, though.

When the problem happens, does the Check Engine Light illuminate as well? You tend to get a high idle when any fault is detected. And does the high idle happen as soon as the "cool coolant" light turns on?

 

Hi, there is no engine check light but from the minute I start the car the blue engine temp light is on constantly and the revs are high. Just trying to get the old dongle to work at the moment. Cheers

 

Hey broski

Take off the radiator cap and see if it gets hot or steams a tiny bit, if not - it is possible your thermostat is stuck open which makes it really difficult to get up to operating temp.

 

Thanks for the suggestion on the rad cap, I’ll give it a go. Cheers

 

Bought an iCar Pro OBD2 dongle, also downloaded Torque Pro but can’t get the App on my phone to talk to the dongle! Despite the fact that the iCar Pro dongle states it works with the Torque App. Frustrating as hell. Flying blind with no idea of what fault codes may be on this car. I should have bought a Toyota Corolla !
by the way, I changed the plugs, changed the ignition coil packs (all eight) no change.
Car blows hot air after a few minutes of running so it is warming up but “blue - engine cold light” remains on constantly.

 

On my Fit, I have a Scan Gauge hooked up all the time so I can keep an eye on important data. Why these cars didn't come with a proper coolant gauge, I'll never know.



I have noticed that in cold weather, using the Defrost will indeed knock the temperature down a surprising amount. But I've never seen it drop so low as to make the blue light come back on (127 F in my car).

I also like the thermostat suggestion. I had a different car years ago where the thermostat was stuck open, and it caused various weird issues. For example, at highway speeds the temp would drop low enough the car thought it hadn't warmed up enough yet and it would come out of Closed Loop, and that would cause the AT shift points to get weird. I'd also get no heat at highway speeds.... I did a long pre-dawn road trip in bitter cold weather and I nearly froze to death in the car! Around town though it was mostly OK.

 

Sorry to hear the dongle isn't playing nicely. Is that a Bluetooth or a Wi-Fi model? I'm still suspecting ECT fault, stuck thermostat, or just excessive cooling due to driving in winter with the AC and heater on. An infrared thermometer can also be handy for quick measurements of the coolant hoses.

One thing to note: as I understand it, the coolant circuit to the heater core on the Fit doesn't have a control valve and the flow is independent of the thermostat, so you might observe some cabin heat even if the thermostat is stuck open.

By the way, I read in the Japanese owner's manual (relevant as many NZ Fit's would be Japanese imports) that the high temperature warning light will flash initially, then solidly at a higher threshold. But, yeah, an actual temperature gauge would be nice! FWIW mine warms up to a pretty stable 84°C and I don't think I've seen it go above 90.