PO125 fault

bobmcc13 · June 28, 2021, 11:05

My facelift 2 keeps reporting a PO125 fault "Insufficient Coolant Temp For Closed Loop Fuel Control"

What does this mean and what is faulty?

I am depending on you for advice It just doesn't make sense.

Temp gauge reads normal, there is enough coolant and car runs OK.

HELP!

Thanks in advance

Bob McClellan

Topdownman · June 28, 2021, 11:29

A bit of background info here;

Background

The coolant temp sensor is very cheap and easy to change so may be worth doing this first unless you are having issues linked to air in the cooling system?

CTS

thetyrant · June 28, 2021, 11:31

Its not the coolant temp its one of the 02/Lambda sensors on manifold not working, think its left hand side as you look in from back of car for 0125 code.

Lots of scanner and online lists report it as coolant issue but on these cars its not and is as above

Gaz mr-s · June 28, 2021, 11:39

Agree with the Tyrant in post above. It's not uncommon. I have seen a code for an O2 sensor at the same time. Do you have a reader @bobmcc13 ?

jonbill · June 28, 2021, 13:22

Agree, p0125 on this engine refers to the heater circuit on either of the precat o2 sensors. They rather reinterpreted the standard meaning of p0125.

bobmcc13 · June 28, 2021, 17:55

Thanks for all the replies. It was at the back of my mind that an 02 sensor would be at the bottom of it.
Time to get rid of the Haas sensors and get proper ones.

Thanks to you all.

Gaz mr-s · June 28, 2021, 19:07

@bobmcc13

https://www.eurocarparts.com/p/denso-lambda-sensor-710828205. Longer cable, but will work in any position. Add the discount & it drops to £28.

Ardent · June 28, 2021, 20:03

That is stonking good.

Shame they are not doing the shorter ones at the same price.

Shame I already have one to fit.

thetyrant · June 29, 2021, 08:10

Quote from: Ardent on June 28, 2021, 20:03That is stonking good.

Shame they are not doing the shorter ones at the same price.

Shame I already have one to fit.

Just to be clear you can use these longer lead sesnors in any of the 3 ports on MR2

I would be wary of such cheap sensors though especially from ECP who seem to be getting a bad rep for fake/branded parts, it might be ok of course but i would rather pay a little more from a reputable seller.... which is not what i would call ECP

Frank Rabbets · June 29, 2021, 09:58

I bought the bottom sensor from autodoc. Quite a good price at £47 delivered. I knew it would not come with the socket.I don't know what type of wire denso use but I could not solder it but had to use the crimp connectors which came with it. I failed on that test so used a length of screwed connector strip.

thetyrant · June 29, 2021, 12:45

Quote from: Frank Rabbets on June 29, 2021, 09:58I bought the bottom sensor from autodoc. Quite a good price at £47 delivered. I knew it would not come with the socket.I don't know what type of wire denso use but I could not solder it but had to use the crimp connectors which came with it. I failed on that test so used a length of screwed connector strip.

All sensors use what i believe is stainless wire which is very hard to solder, crimping as you found is the answer for joining it and to be fair in an automotive environment crimping with quality/suitable connectors (no splice in t-taps!) is better anyhows in most areas.

Ardent · June 29, 2021, 17:15

Quote from: thetyrant on June 29, 2021, 08:10[
Just to be clear you can use these longer lead sesnors in any of the 3 ports on MR2

Yeah appreciate that, but would play on my ocd, knowing there is the extra un need wire. Even if neatly folded. And not trusting myself to solder them.

Gaz mr-s · June 29, 2021, 18:19

Quote from: Ardent on June 29, 2021, 17:15
Quote from: thetyrant on June 29, 2021, 08:10[
Just to be clear you can use these longer lead sesnors in any of the 3 ports on MR2
Yeah appreciate that, but would play on my ocd, knowing there is the extra un need wire. Even if neatly folded. And not trusting myself to solder them.

They don't get soldered...the wire doesn't take it.

Ardent · June 29, 2021, 23:13

exactly

Frank Rabbets · June 30, 2021, 08:33

Perhaps SS is used because it does not conduct heat very well c/w copper. The sensor must get very hot as it is on the exhaust manifold. Copper might heat up too much and melt the insulation in the sensor loom.

bobmcc13 · July 16, 2021, 15:46

I have taken note of all the advice already received thanks. But I am now getting really cheesed off with this P0125 fault now.
I've changed the cheapo HAAS 02 sensors for Denso but the fault still reappears within a few hundred meters of starting off.
Has anybody any idea of how to get rid of this really annoying fault.
All the wiring (What you can see of it) seems to be in order.
We do have a canal just down the road that seems to have space in it.
Any ideas would be appreciated.
Thanks in advance.

Bob McClellan

Carolyn · July 16, 2021, 16:05

If it were me, in your position, I'd be swapping out the temperature sensor -just to see if it has an effect.

there are a couple of earth bundles that bolt to the Cylinder head, at the left-hand end as you look at the engine. They rarely cause a problem, but a quick clean -up might also assist.

Ardent · July 16, 2021, 20:52

@bobmcc13

You have a pm

bobmcc13 · July 17, 2021, 17:57

Ardent
Thanks for your PM it makes things a little clearer, I will have to study it in detail.

Thanks again.
Bob McC.

Ardent · July 22, 2021, 20:56

We're the readings taken when hot?

Not just idling. Think the post is ignored until up to temp. Might account for figure.

What code did it give you?