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Discussion Starter #1
I had the dreaded ping and engine light come up on my 1.8EX 2006 a couple of weeks ago so have invested in a Delphi DS150E Diagnostic kit and have got the P2185 code with Engine Coolant Temp 2 Sensor Fault.

After reading up on it I see the possible harness issue and sensor issue, in an attempt to help others and stop people freaking out when they get this I decided to do some investigation.

Firstly, I cleared the code, ran the car for 1/2 an hour, rechecked with diagnostic, all fine.

I removed the undertray and checked the connector which looks to be ok so sprayed with WD40 and applied some barrier silicon grease to protect, reconnected and still no engine warning light after another 1/2 hour run. All good so Far.

It looks like the cause could have either been temporary or a faulty sensor.

Now for the good bit...... As all was working ok and checking previous posts, the issue with installing a new connector, soldered on seems to worry all with the increase of resistance etc. I am an electrical engineer and understand it quite well. So when the connector gets corroded, the resulting weak connection along with the 2 conductors rubbing together may cause a quick spike in the circuit (imagine rubbing the positive conductor on a battery, you get sparks) which could alert the fault.

The solution to solder on a new connector could cause the fault by increased resistance in the circuit as in theory, the sensor itself is sending a signal by means of resistance. When the coolant gets hot, this changes the resistance in the circuit ultimately closing a relay which will activate the electric fan. Adding in a small amount of solder will change the resistance in the circuit but if its a good soldered connection with minimum amount, the change in ohms would be milli ohms.

I decided to try and force the fault by increasing the resistance. Basically, I have removed some of the insulation exposing the copper cable where you would cut the cables if you were to splice/solder in a new connector. I have then introduced some solder to the now bare wires, mimicking a soldered joint, wrapped the bare joints with an insulation barrier and restarted the car. NO BING and all is well so far. I will leave it like this for a few weeks and see if it comes back as my next port of call will be to replace the Sensor (I think its faulty anyway so have ordered one up from Honda) .

I am hoping my test will prove that the wires can be cut so long as the new connectors wires are the identical length of the faulty and removed connector, then soldered PROPERLY with a very thin end to end type soldered joint.
 

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i don't see how adding a bit of solder to a continuous piece of wire will effect the resistance at all

i do understand that corrosion will alter the integrity of the connection and could effect the contact resistance or cause open circuit in the extreme cases but soldering a new connector in place shouldn't alter anything providing the job was done properly
the length of wire used on the new connector wouldn't be important
to get a resistance difference that might affect the sensor reading you would have to use many feet of wire a few inches difference wouldn't matter

but....

saying all that a faulty sensor is a faulty sensor and no amount of fiddling with bits of wire or connectors is going to change that
 

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Discussion Starter #3
That's the point, honda say the harness needs replacing if the connector is corroded. I am trying to see if the added solder will cause the fault or not. I don't think it will.
 

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That's the point, honda say the harness needs replacing if the connector is corroded. I am trying to see if the added solder will cause the fault or not. I don't think it will.
it won't

honda will not solder a new connector on to an existing harness hence telling you the harness needs replacing for the sake of a corroded connector but there's nothing stopping you from soldering a new connector on to the existing harness

the only thing to be wary of is wiring harnesses tend to degrade over the years you will see that some wires can blacken ( usually ones carrying current ) that make them difficult to solder
a good rub with some wet n dry sand paper can help as well as a bit of flux to help clean the wire
don't forget to use some heat shrink tubing to insulate the wires when your done
 

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Discussion Starter #5
Again, the point to check was due to a lot of people being told about soldering in a new connector where the solder increases the resistance which may cause a fault. This is even noted in the WIKI. As I had the fault, I was doing some investigation to try and assist others that when this happens, you do not need a new harness and not to panic. I have learnt my lesson and wont be trying again.
 

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My last Civic through this fault up had the connector cut off and new one soldered on. Never a problem after.

I think its the same connector that's used on the Jazz mirror/indicator. The Honda garage said quite common and out of warranty they always just replace the connector.
 

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Solder sucks. Weather proof heat shrink terminals. Cut back the wire until you find clean copper and crimp heat shrinks on and heat with a heat gun, if done correctly the repair will last the life time of the vehicle.
 
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