Aygo Ecu ground location ?

[Markie1881]

Hi all , it’s my 1st post so be gentle with me . I have an aygo 1.0 and I have a B2799 fault code that tells me the imobiliser is not communicating with the Ecu hence it cranks but won’t start ! I’ve swapped out Ecu,  immobiliser Ecu, key chip from a known to be  working car and got exactly the same outcome.  I think I worked out with the help of Google I have a broken wire somewhere or a bad earth ! Can somebody tell me where the Ecu s are grounded ? Any help greatly appreciated . Many thanks mark  

[gampla]

1 minute ago, Markie1881 said:

Hi all , it’s my 1st post so be gentle with me . I have an aygo 1.0 and I have a B2799 fault code that tells me the imobiliser is not communicating with the Ecu hence it cranks but won’t start ! I’ve swapped out Ecu,  immobiliser Ecu, key chip from a known to be  working car and got exactly the same outcome.  I think I worked out with the help of Google I have a broken wire somewhere or a bad earth ! Can somebody tell me where the Ecu s are grounded ? Any help greatly appreciated . Many thanks mark  

Ecu ground is normal found at Battery

[Markie1881]

I’ll have a look cheers 

[flash22]

The ecu is directly grounded but it's more than likely the signal ground,

i will dig up the diagrams shortly

[Markie1881]

Great any help greatly appreciated 👍 thank you 

[flash22]

2 earth points iirc both located behind the fusebox and ECU

B2 - near the passenger suspension on the firewall

B3 - passenger side on the firewall

[Markie1881]

Thank you I’ll have a check tomorrow . Cheers mark 

[Markie1881]

I’ve had a check and cleaned them up , but still no start ! I’m really starting to pull my hair out on this one . Has anybody had the same problem and fixed it ? Cheers 🍻 

[flash22]

Usually it's a broken or partially broken wire, it may test fine under continuity but not under load

you have too many variables with parts swapping, put back the original ecu, immobilizer and chip in the key

you need to check the continuity and resistance of the violet and green wires from the immobilizer (pins 12 and 13) to the ecu (pins 39 and 6) there are 2 other connectors in this circuit as well AC1, BA2

 

does your interior light work as it should (driver's door)

[Markie1881]

But I’ve not got a green and violet at my immobiliser box ?

[flash22]

There was a colour change mid 2010 - yours has the 08 to 2010 colours

Immo (Pin 12) - Pink goes to violet on the ecu (Pin 39)

Immo (pin 13) - beige goes to green on the ecu (Pin 6)

these pass though 2 different wiring combs (4Q and 4C)

 

[Markie1881]

Many thanks your a legend , really appreciate your help 👍

[Markie1881]

Ok I’m getting continuity now but I’m not sure on pin numbering ? Mark 

[Markie1881]

Can you clarify PIN numbers on Ecu plug , I think I’m getting somewhere now . Cheers 

[Markie1881]

Pink immo is going to green with paper clip in on Ecu plug 

[Markie1881]

Beige on immo is going to purple on Ecu as per photo below 

resistance on both is 0.3 ohm 

[flash22]

check continuity and resistance from immo to ground (white/black stripe)

[flash22]

Immo is grounded to C2, the diagram isn't clear but look like its bolted to the firewall inside the car behind the heater box

 

[Markie1881]

White black stripe from immo plug to ground have continuity and between 0.1 and 0.2 ohms resistance cheers 

[Markie1881]

I’ve added an extra ground to white black cable still nothing 

[flash22]

Check the resistance and continuity of the coil around the barrel

otherwise, check the 3 powers to the immo

[Markie1881]

Yep I’ll give all that a go 👍

[flash22]

kgb10 immo.pdf

[Markie1881]

Absolutely fantastic , it’s a bit hot today to be in the sun so I’m going to have a real go tomorrow . Armed with wiring diagrams makes sense more . Thank you I’ll keep you updated 👍

[Markie1881]

Hi had a real good go at this today , everything is looking good apart I can’t locate plug A35/A36 says engine Ecu . Only have 2 plugs on my Ecu . Can you help with location . Cheers mark