Engine & Gearbox Intermittent engine malfunction light - temp sensor?

Discussion in '1st Generation (2004-2011)' started by ec5779, Wednesday 11th Sep, 2019.

  1. ec5779 Junior Member ☆ ☆ ☆ ☆ ☆

    United Kingdom ec5779 London
    14
    6
    Hello
    We have a 56-plate F-RV, 2.0l petrol (K20A9 if I'm not mistaken), and the engine malfunction indicator light has come on a couple of times so far.
    Not sure if this is relevant, but this started a couple of days after we got back from a holiday - we left our car for 8 days near the airport.

    A 60 mile drive back from the airport in the middle of the night passed totally uneventfully, cruise control practically all the way and unusually good fuel consumption reading on the display - 41.2mpg by the time we got home which is very high for this car, but just about within expectations, helped by 50mph speed restrictions due to roadworks.

    Two days later (Sunday) the malfunction indicator light appears (the car had only done a couple of short journeys in between). The next evening (i.e. Monday), the light went off on the way back from work.
    We didn't use the car the next day (yesterday), but the day after (i.e. today) the light came immediately back on, and then went off again within 30-45mins later. Took it to a garage who found a stored code even though the MIL had gone off: P2185 Engine Coolant Temperature Sensor 2 Circuit Voltage High. He said wait and see what happens over the next few days. Haven't used the car since but we'll see what happens tomorrow.
    qui
    Besides the light, the car has been driving normally, perhaps a slightly unusual noise idling (like a few tiny gaps where the engine cuts out for a fraction of a second every couple of seconds) when the engine is cold but besides from that nothing unusual.

    My thoughts:
    1. So far the light has only initially come on when the is engine cold (though it stays on after it warms up)
    2. Second time the light came on it went off much more quickly than the first time, perhaps its just a weird quirk after not being used for a week, or a sensor on its way out but if regularly used might keep working for a bit
    3. Or, perhaps both the above are totally irrelevant and its just completely random
    Any initial thoughts please? I'll try to remember to keep you posted either way.
     
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  2. Craig830 Club Member ★ ☆ ☆ ☆ ☆

    United Kingdom Craig Rothbury
    25
    23
    1
    Item 18 in this link is the engine block sensor:

    https://www.parts-honda.uk/honda-ca...GINE/WATER-PUMP-20L-/17SJD501/E__1501/1/20511


    Item 11 in this link is the radiator sensor:

    https://www.parts-honda.uk/honda-ca.../RADIATOR-20L--TRAD-/17SJD501/B__0501/3/20511


    One of these two is Sensor 2, and is possibly on its way to failure. Before replacement however, i would remove the electrical connectors, give them a squirt of contact cleaner and give the wiring at them a check for corrosion. If the problem doesn't go away after this you will need to replace the failed one (you'll need to do a bit of research into which is number 2 though)
    - - - Updated - - -
    I forgot to add that i had coolant sensor failure on a Rover K-Series years ago, and had rough running when cold.

    Its because the ECU doesn't have a usable value for engine temperature so defaults to a 'safe running' value, a sort of limp home setting. It will explain the odd fuel consumption (running at reduced power) when warm, and the odd cold start idle (engine is colder than the default value suggests, and air/fuel mixture is therefore incorrect).

    Hope you get it sorted soon, a quick google shows both sensors can be replaced from these links for less than 20 quid:

    https://www.onlinecarparts.co.uk/oenumber/37870raaa01.html

    https://www.onlinecarparts.co.uk/oenumber/37870pna003.html
     
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  3. ec5779 Junior Member ☆ ☆ ☆ ☆ ☆

    United Kingdom ec5779 London
    14
    6
    @Craig830 Thanks so much those diagrams are so useful!

    Sadly, I don't really have the experience, confidence or equipment to be able to tackle this myself - but I wish did, if I've understood correctly, once you manage to get to the relevant sensor, it should be a fairly easy job. (That does assume that its relatively easy to get to the sensors in question).

    Thanks again for getting back to me, I'll try to keep everyone updated what happens.
     
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  4. Craig830 Club Member ★ ☆ ☆ ☆ ☆

    United Kingdom Craig Rothbury
    25
    23
    1
    No problem, if you need any advice just ask
     
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  5. MattBeardless Service Team H-Tune Staff

    Drop us an email to sales@h-tune.co.uk with a link to this thread and we'll look into sourcing them for you for a great price. :Smile:
     
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