Aygo Ecu ground location ?

[Markie1881]

These were the buggers !

[flash22]

Not sure what they are actual for in that location

[flash22]

Found it, you can't of had a good spark unless it was pulling a ground from elsewhere - there's the white/black and brown

[diarmaidcormack1]

Just been reading through this I have the same problem. Was these wires under the air box causing the b2799 code? 

[Markie1881]

57 minutes ago, diarmaidcormack1 said:

Just been reading through this I have the same problem. Was these wires under the air box causing the b2799 code? 

Hi loads of people looked at my aygo and could not find the fault ! But I found it !!! As you look at the engine to the right there is a loom strapped to the head , there are 2 wires that come off that loom and are earthed to the block /head via an o ring . It’s a 10mm bolt underneath , my wires had become detached via vibration and age . They are the earths for the injectors . Mine just turned over would not fire or start , remade the connection and fired up straight away . Only took 5 months 3 garages . But I found it ! If you need any further help give me a shout and I’ll try and take some pics for you 👍

[flash22]

See my posts above, it shows what is connected to that earth point that could give you some direction

[Mjolinor]

I am having none start problems on an Aygo and they seem very similar to this thread.

I have checked wires etc etc but would like to know where the signals on the two immobiliser wires are sourced.

From the signals I surmise that one is clock and one is data.

Is it:
Clock = ECU source
Data = Immo source
or
Clock = Immo source
Data = Immo source
or
Clock = ECU source
Data = bidirectional
or
Clock = Immo source
Data = bidirectional

I cannot find the answer anywhere else so hopefully the answer is here.

I have a very small clock and no data so I am thinking if it is ECU sourced clock my  immobiliser may be OK and it is just not getting the clock signal.

 

[flash22]

Pre 2009

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) and 2 connectors

2 serial bus lines 1 in, 1 out

 

Diagram on the first page

the wires under the air box, give them a good hard tug the wire may be internally broken

Also probe the negative on the coil or obd2 (dlc3) pin 4 (positive on a power source) and crank to see if the voltage drops off

 

I take it you have ruled out the crank and cam sensor and have no spark

 

[Mjolinor]

I have ruled out crank and cam. Both signals there are as they should be. (see pic)

 

I have opened the ECU and the immobiliser and have continuity for both lines from PCB to PCB.

 

I have no data on either line, hence the question, which are the source so I can get to checking PCB tracks. I suspect that pin 12 on the immobiliser is sourced a the ECU and pin 13 on the immobiliser is sourced from the immobiliser but would like someone to confirm.

 

[flash22]

You only get packets sent from the immobilizer once it detects the key

IMO your over thinking it

did you do anything before this issue started, like changing fob batteries ?, confirm the immobilizer chip is in the key

[Mjolinor]

There are no batteries.

 

Delphi says immobiliser is there and detecting key correctly (master) and immobiliser is going inactive. Turning it off or removing the key results in immobiliser going active.

 

Immobiliser to computer is by the OBD port and does not go through the ECU. The ECU has no faults and still has no faults if I leave the immobiliser PCB unplugged.

 

 

[flash22]

Has the car been jump started ?

The fact the immobilizer is telling the ecu what it's doing shows that it's communicating in both directions

[Mjolinor]

The immobiliser is not telling the ECU, the immobiliser connects to the OBD so talks direct to Delphi and that does not involve the ECU as far as I know.

The car has been jump started the last time it was running.

 

[flash22]

25 minutes ago, Mjolinor said:

The immobiliser is not telling the ECU, the immobiliser connects to the OBD so talks direct to Delphi and that does not involve the ECU as far as I know.

The car has been jump started the last time it was running.

 

That is incorrect, the immobilizer is connected directly to the ecu fuel and spark is all controlled by the ecu it connects via k-line rather than canbus depending on the age

 

Disconnect the alternator and see if it starts, jump-starting can blow the ALT fusible link and/or blow/weaken the reg on the alternator

 

[Mjolinor]

 

I just swapped the ECU set and now have immobiliser signals that were not there with the original ECU.

Still no start.

This is an old fault (more than 5 years). It would occasionally fail to start then left a day or an hour or a week it would suddenly work. It failed in about January and sat outside my sister's house until last week when I jump started it, drove it may 20 miles with lots of stops and starts then took it home. The morning after it failed to start and has not started since.

 

 

[Mjolinor]

Why does the ECU not log a fault if I try to start with the immobiliser unplugged?

The Internet says it does but this one certainly does not.

[Mjolinor]

Alternator disconnected, no change.

Cranking voltage is 10.9 volts measured while cranking after about 10 seconds.

The immobiliser goes active after the ignition has been on for 10 seconds. I am not sure I expected that. It does the same while cranking.

 

[flash22]

Can you hear the fuel pump prime, do you have spark ?

[Mjolinor]

No spark. Fuel pump activates when cranking and shifts plenty of fuel. Took the end off the fuel rail and it spews plenty out.

There does not seem to be any measure of fuel pressure available but I am pretty sure it will be OK.

[Mjolinor]

I do occasionally get a crank sensor fault. It has always done this and has had two new crank sensors. I am beginning to wonder if the wires from the crank sensor to the ECU are intermittent. The trace above was taken at the sensor and as it is a voltage generating sensor that will be the same whether or not it is connected to the ECU.

I can't find which pins on the ECU it connects to.

 

[flash22]

Put in a temp ground on the white/black at one of the coils

[Mjolinor]

Ground is good. I checked all three coils and rived the wiring about. Also checked the actual wire front right (as you look) of the engine.

I will try it shortly but I don't think it will do anything. Are the three coils sharing a common earth so I just need to connect to one of them?

[flash22]

They share the same ground, the wiring may test good with a meter, but that doesn't mean they can carry current

CPS - before late 2008

Pin 27 - Pink+

Pin 8 - Light Blue -

these are on connector A (immo is on connector B)

as it's not throwing code(s), it seems like a ground issue

 

 

[Mjolinor]

It is a 2009.

I checked the grounds while cranking. Voltage between negative on Battery and engine block and coil earth connection with the coil connected.

[Mjolinor]

Wiring to CPS is solid.