Hi, I’ll start with an explanation of what’s happened. Our 2015 1.2 yeti had flagged up a P0036 code (heating circuit) 

i sourced a replacement oem lambda sensor & fitted it today, after clearing the code i went for a test drive & the same code returned!

suspecting that the lambda wasn’t at fault and something else was amiss I went through the under bonnet fuses checking for any blown ones, after they all checked out ok i thought I’d clear the code again to see if there was any change - there was as the car now won’t start.

I’ve got electrics for the fan/windows/lights etc but the warning lights in the instrument binnacle are all out & the starter won’t engage.

The battery is fine & the car has only covered 33k miles, I’ve checked the battery terminals & the interior fuse board with nothing found.

the only thing that concerns me is when checking the fuses i replaced some of them in different places accidentally as our car has many vacant positions, surely this couldn’t cause any terminal damage?

Any advice gratefully received.

rob

Did you turn the ignition on before realising any of the fuses were in the wrong place?  Most likely thing is that you have blown one or more.

1 minute ago, Zib said:

Did you turn the ignition on before realising any of the fuses were in the wrong place?  Most likely thing is that you have blown one or more.

Don’t think so, i rechecked all fuses for a second time & they’re all fine - that’s making me think the fuse mistake might be a red herring I’m worried about for no reason.

Something has knocked out all the engine electrics though, even the obd port is dead.

rob

Sounds like you may have moved a critical fuse to a wrong (and vacant) position?

Edited 21 May, 20224 yr by muddyjim

3 minutes ago, muddyjim said:

Sounds like you may have moved a critical fuse to a wrong (and vacant) position?

I agree, but i can’t find a diagram of my cars fuse board-the only ones I’ve seen have been fully populated boards for fully specced cars?

Rob

Take a close look at the empty spaces in the fuse board:

- if it has no contacts, perfect

- if it has a single contact, that's fine

- if it has contacts on both sides, it's missing a fuse

 

At a complete guess, I'd check fuse 12 (5 amp?) in the engine bay as I think that's the CAN gateway. It would explain both the no start and lack of OBD...

58 minutes ago, langers2k said:

Take a close look at the empty spaces in the fuse board:

- if it has no contacts, perfect

- if it has a single contact, that's fine

- if it has contacts on both sides, it's missing a fuse

 

At a complete guess, I'd check fuse 12 (5 amp?) in the engine bay as I think that's the CAN gateway. It would explain both the no start and lack of OBD...

I’ve received a pic from my brother in law, if you can see the small orange 40a fuse on the r/h side - i had placed that 1 position higher than it should be with the above results!

I’ve still got the annoying p0036 code pending despite replacing the sensor but at least the car’s working.

thanks for the suggestions.

rob

It's always a good idea to take a photo yourself before you start taking something apart, especially if you don't have any actual documentation as to how the thing is supposed to go back together!

58 minutes ago, ejstubbs said:

It's always a good idea to take a photo yourself before you start taking something apart, especially if you don't have any actual documentation as to how the thing is supposed to go back together!

 

I couldn't agree more! In fact I've lost count of the number of times I've reminded myself of this...

 

...after the event 

Double-check the bottom right red one, fuse 15. That looks to supply the heaters of both lambda probes.

On 23/05/2022 at 11:49, Breezy_Pete said:

Double-check the bottom right red one, fuse 15. That looks to supply the heaters of both lambda probes.

thanks for the info, I’m still getting the code. I can clear it with my scanner but it remains pending & flags up the warning light after a couple of trips.

I’ve examined the wiring the lambda plugs into & am now investigating the ecu behind the wiper cowling, it looks as though i may have mice!

the pesky security clamp needs removing before i can check the pins in the plugs for corrosion damage 

 

You don't say whether or not you've double-checked the fuse I mentioned. Did you?

 

6 minutes ago, Breezy_Pete said:

You don't say whether or not you've double-checked the fuse I mentioned. Did you?

 

Yes, i checked all fuses for continuity.

rob

Dont disturb the ECU, there is not a better protected connector known to mankind.

 

Start looking for the cables the mice have chewed through

Just now, J.R. said:

Dont disturb the ECU, there is not a better protected connector known to mankind.

 

Start looking for the cables the mice have chewed through

Ok, i thought it could be linked to corrosion but you think that’s unlikely?

I haven’t seen any rodent damage so far but will continue looking.

rob

If you want to continuity-check wiring I can probably find the pin numbering details for you as reqd. Well worth looking thoroughly for external, visually-apparent wiring damage first though, as said.

21 minutes ago, Breezy_Pete said:

If you want to continuity-check wiring I can probably find the pin numbering details for you as reqd. Well worth looking thoroughly for external, visually-apparent wiring damage first though, as said.

cheers Pete, I’ve had my meter on the post cat lambda plug & measured 12v so I’m suspecting an Earth/return issue causing the fault code?

rob

Yes, that's quite possible/likely. The way the heaters work is that they get a constant 12V feed on one side of them, then the ECU modulates the return/ground path on/off in Pulse Width Modulated fashion to provide easily (digitally) controlled currents through each heater. 

17 hours ago, Breezy_Pete said:

Yes, that's quite possible/likely. The way the heaters work is that they get a constant 12V feed on one side of them, then the ECU modulates the return/ground path on/off in Pulse Width Modulated fashion to provide easily (digitally) controlled currents through each heater. 

thinking about it, the fuse couldn’t be the issue if it feeds both lambdas as I have a p0036 code relating to one lambda only?

I’ve had another dig about today & despite the warning that’s been posted on this thread i thought it would be silly not to discount a corrosion issue on the pins.

the plugs came out easily after dremeling a slot into the security screw that holds the plugs captive, nothing stood out and no damaged wiring apparent either. I’ve also cleaned the ground wires at various locations under the bonnet.

it’s a 2015 car with only 33k, it’s a little disappointing having a problem like this to be honest - I’ve only recently had to replace the water pump as well!

i cleared the codes with my scanner & the engine light has reappeared again after a couple of short journeys. I’m getting fed up with this now.

 

Continuity test info:

Precat lambda heater is white wire from sensor conn pin 3 to 94 way ECU plug pin 7

Postcat sensor heater also a white wire, from (its) sensor conn pin 2 to 94 way ECU plug pin 29

 

Agree with your logic about shared fuse feed.

 

STOP PRESS: there's more than one engine code you may have in a 2015 1.2. The above is for CBZB, but you may have a CYVB, please confirm which. See here if you don't understand what I'm talking about.

 

Edited 28 June, 20223 yr by Breezy_Pete

29 minutes ago, Breezy_Pete said:

Continuity test info:

Precat lambda heater is white wire from sensor conn pin 3 to 94 way ECU plug pin 7

Postcat sensor heater also a white wire, from (its) sensor conn pin 2 to 94 way ECU plug pin 29

 

Agree with your logic about shared fuse feed.

 

STOP PRESS: there's more than one engine code you may have in a 2015 1.2. The above is for CBZB, but you may have a CYVB, please confirm which. See here if you don't understand what I'm talking about.

 

 

hi Pete, it seems we have a cyvb variant 

 

 

I'll copy/paste the above wiring statements suitably corrected for you.

Looks like they ditched the wideband pre-cat sensor in favour of a cheaper 'normal' one on this later code. 

 

Precat lambda heater is white wire from sensor conn pin 2 to 94 way ECU plug pin 7

Postcat sensor heater also a white wire, from (its) sensor conn pin 2 to 94 way ECU plug pin 28

 

I thought I’d post an update to my post, after struggling to clip the bulkhead trim i used to much force & cracked the windscreen ☹️

that’s when i lost my enthusiasm for the job & took it to a local specialist, the fault was fixed by fitting a new lambda sensor (another one) the Bosch sensor i purchased from autodoc was faulty from new.

we live & learn.

rob