[Mk2] [Turbo] Oxygen Sensor Differences - Error code 21

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killerferret666
Posts: 659
Joined: Thu Jul 26, 2012 8:00 am

[Mk2] [Turbo] Oxygen Sensor Differences - Error code 21

Post by killerferret666 »

The Gen 2 / Gen 3 use different oxygen sensors, in terms of 1 is 1 pin and the other 4 pin (2 heating wires)

when I got my engine (gen2) which had a Gen 3 wiring conversion it still only had one wire for the oxygen sensor, I don't know how but it did and confirmed that wire went to the OX pin on the ECU. So used the Sensor already in the exhaust.

Do the Gen 2 / Gen 3 ECU's expect a different input signal?? value and hence I'm getting the above error. I suspect its always been there, its always ran rich.

Or do the oxygen sensors give out different readings?

If I were to switch to a later Oxygen sensor, It looks like I don't need the heater element to it (its just for warm up) and can just ground the 2nd pin and connect the single wire as expected.
My Blog on Miami GT4 kit car build using MR2 Donor Car

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twitter for photo's as I'm building -
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killerferret666
Posts: 659
Joined: Thu Jul 26, 2012 8:00 am

Re: [Mk2] [Turbo] Oxygen Sensor Differences - Error code 21

Post by killerferret666 »

After a lot of investigation I have the answers.

The sensors work the same...however the ECU is expectign a heating element to the Sensor and will throw the error 21 if it thinks the heating circuit is open or short circuited.

so having a 1 pin Oxygen sensor means its always been running rich :mad:
I know why this wasn't picked up before and that's because the engine is a forged one and they were probably running a wideband with the larger turbo etc...

The good news it isn't too hard to fix and change to the 4 wire one

Black wire - already sends signal to ECU

Wire the 3 below new wires if cant be found;
Earth wire - Brown on the normal loom so can splice in to a brown wire
Signal to ECU - Red / White, there is a HT input into the ECU, I will have to trace this wire back and splice on to that if required
Yellow / Black - Splice on to any point of the Yellow and black.

this should then solve this problem
My Blog on Miami GT4 kit car build using MR2 Donor Car

http://miamigt4kitcar.blogspot.co.uk/

twitter for photo's as I'm building -
www.twitter.com/iwanabeaferret
killerferret666
Posts: 659
Joined: Thu Jul 26, 2012 8:00 am

Re: [Mk2] [Turbo] Oxygen Sensor Differences - Error code 21

Post by killerferret666 »

Easier solution implemented rather then all that wiring.

I found that my cabling didn't even have a Pin in the ECU connector for the Lambda sensor heater wire, so I got a pin from an old plug and then soldered a 6k Ohm Resister + a 1.5k Ohm resistor in series to it.

I then put this in the correct position in the plug and connected the other end to a Black / Yellow wire via splice.

Reset ECU, took it out for a drive...

Now I no longer get an o2 Sensor error, problem solved and the car runs much better as well
My Blog on Miami GT4 kit car build using MR2 Donor Car

http://miamigt4kitcar.blogspot.co.uk/

twitter for photo's as I'm building -
www.twitter.com/iwanabeaferret
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