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MadDogMoggy 26th July 2012 15:18

Hondata Error - 2nd 02 Heater
Hi All,

Engine rewired and re-plumbed now (Honda K20A2).

Had some issues with error codes on the Hondata system. Turns out I had a broken wire going to the ECT sensor which is now fixed.

I now have errors for the 2nd O2 sensor - I've cured the one for the sender by switching it off in the software, but it still reports an error for the heater for the 2nd o2 sensor and illuminates the MIL.

Any ideas how to cure this? (short of unplugging the MIL!)


eaa53 27th July 2012 16:53

It is taken for granted that the sensor is a good one! ie swapped the 1st and 2nd over and still have the same problem?

If no cat is fitted between them the second sensor may be trying to tell you the cat is not working, good of it to notice.

You can buy lambda sensor eliminators if the reason that the sensor is giving a true and realistic message that you do not want to see.

The other technical alternative is Technical Topics ( Bridgwater, James will know what its telling you and likely how to fix it, once its hooked up to his kit that is.


MadDogMoggy 27th July 2012 17:40

Thanks for the info, but the problem's not with a sensor - the sensor isn't attached.

The Hondata system allows you to set it so that the 2nd O2 sensor doesn't throw up an error (as there is no sensor it does this) but doesn't allow you to turn off the error generated by the 2nd O2 sensor heater not functioning (because it isn't there!)

My system has a pre-cat O2 sensor which is rigged up as the primary sensor (or Air/Fuel Ratio Sensor) but no post-cat sensor.

I know others have set up their systems with Hondata and wondered how they got over this?

Thanks again

alackofspeed 29th July 2012 10:44

I haven't fitted a second sensor, and it is disabled in hondata. No error.

What have you got selected in the 'misc' tab? should be nothing in ecu options area.

MadDogMoggy 29th July 2012 19:38

I'm running the latest software version (3.1.2 I think).

Under Misc/ECU there are four options:

Immobilizer enabled
Purge system

Apart from Purge they are all off (OBDII being the one that disables the secondary O2 sensor). Choosing this stopped errors about the Secondary O2 Sensor voltage, but not for the Secondary o2 Heater malfunction (which I assumed it would as if you have no sensor you have no heater for it!).

I'll turn off purge if that's working on your system.

Thanks for the info - I may try turning OBDII back on then off again and see if that works.


alackofspeed 8th August 2012 22:25

Any progress?

Presume you're trying to capitalise on some free time during the school holidays. My recollection is you're not far from Dorchester, so I could pop over with my car one evening and compare ECU settings.

MadDogMoggy 9th August 2012 23:39

Not played with ECU as I've had to reinstall everything onto the laptop I was using to run the Hondata software - hoping to give it a go tomorrow!

I've also read somewhere about fitting a resistor to one of the ecu pins to mimic a heater, but this may be specific to American ECUs.

I'd welcome the chance to have another chat and look at your car, and to see how your ecu is set up. I'm about 3 miles outside of Dorch, and you'd be welcome to pop round anytime you fancy giving your car a quick blast.

Dad and I have been trying to get as much work done as possible over the hols so far. Starting to see the light at the end of the tunnel!


alackofspeed 9th August 2012 23:53

Righto. I'm away until the 20th, but could pop by after that. I'll drop you a PM nearer the time.

MadDogMoggy 10th August 2012 17:56

Brilliant - look forward to hearing from you.

Reflashed ECU today and it cured the secondary O2 problem, but primary O2 now occasionally comes up with a low voltage error. When cleared its ok for a minute or two then comes back!

Ric H 15th August 2012 22:40

Glad you got the sec O2 error fixed. My experience is reflashes cure all sorts of ills! I get the occasional primary O2 error. My own experience is it tends to be a poor connection. Not sure of my facts here, but I suspect the O2 signal wire may be at pretty low voltage and may be most prone to error due to high resistance at connections.

MadDogMoggy 15th August 2012 23:53

Cheers Ric - I'll look into that. The sensor has a 'waterproof' plug fitted to it (which is one of those make it up yourself jobbies) so that may well be the problem.

Thanks for the tip


alackofspeed 4th October 2012 20:03

I have recently changed to the latest version of Hondata and have no warning lights. I've also developed a calibration which as appreciably improved my engine's driveability and power.

You are welcome to a copy of the calibration. If we get a decent weekend in the near future I am still interested in a run down to view your build.


MadDogMoggy 10th October 2012 10:00

Hi John,

In the throws of trying to get the car ready for IVA at the end of the month. Screen in, wiper and washers fitted. Just fiddly bits and bodywork tidying mainly, but ECU light occasionally comes on so a visit would be most welcome!


alackofspeed 19th October 2012 21:56

Oops, I failed to spot the last message.

By all means phone me (I'll send a PM with the number), and we can arrange. Weather looks suitable this weekend, and Sunday is feasible for me.

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