Xsara Picasso wiring diagram? Car won't start

[JamesQB]

Hello,

Xsara Picasso 1.6HDi. Car is in Spain where they were sold for longer than in the UK, so it's a 2013 but seems identical to the ones sold in the UK until 2010.

It was intermittently cutting out while being driven and then refusing to start -- turning over but not catching. Required a tow truck to take it home where it would often then start, sometimes a few days later though, after trying it each day. It would state "immobiliser error" when cutting out.

Broke down again 2 weeks ago, towed home, now the problem seems permanent.

This issue started in January. The Lexia has found two logs. No fault codes for the errors, just explanations and mileage for first and last occurrences with total number of events:

- Permanent fault. Communications fault between the built-in systems interface (BSI) and the ECUs on the COMFORT VAN.
- First recording 142881 Km.
- Last recording 151791 Km.
- Number of occurrences 8.

- Permanent fault. Communications fault with the engine management ECU.
- First recording 148344 Km.
- Last recording 151830 Km.
- Number of occurrences 7.

The second fault's "first recording" mileage of 148344 Km matches when the cutting out problem started. The "last recording" mileage of 151830 Km is the car's current mileage showing on the odometer. So it seems the problem is a communications fault with the engine management ECU?

Wiring diagrams are hard to find. Could anyone help with diagrams or with how to approach this fault please? The car still will not start, just turns over.

Thanks

[wheeler]

Would need the VIN to get correct wiring diagrams, also you would need to state which circuits you require.
Strange that it would say immobiliser fault as it cuts out as the immobiliser only needs to be unlocked for initial starting, The immobiliser prevents starting but will not stop the engine whilst its running.
With Lexia can you currently talk to the engine ECU & BSI?
Battery terminals tight?
Any signs of water ingress in ECU or under bonnet fuse box plugs?

[JamesQB]

VIN is VF7**************[VIN obfuscated, can be read by forum staff] and need circuits for BSI and ECU especially power supply and communication lines to and from ECU please.
Unsure about the immobiliser message as I'm getting information from someone else. Engine stalls when communication is lost between BSI and ECU. This communication was being lost intermittently but is now a permanent loss.
Lexia communicates with the BSI, but cannot communicate with the ECU currently.
Battery terminals tight. Engine turns over normally, but does not start.
No signs of water ingress in ECU, ECU connectors, or the underbonnet fuse box.

[PaulC5]

Have you tried replacing the crank shaft sensor, these can fail and give symptoms like yours and the communications fault messages might be nothing to do with it stalling/not starting until possibly it has cooled down.

[wheeler]

I’ll sort out some diagrams tomorrow.
If no coms with ECU the chances are a loss of power supply to ECU. The most likely culprit would be the under bonnet fusebox (BSM). This incorporates the main relay that supplies the ECU with power.

[wheeler]

Sorry i can't post the diagrams in the original format as the forum dosent allow it. So done it in 2 half's.
This is the injection diagram. There is not a diagram for the BSI as such, you really need to pick the system you want & the relevant connections to the BSI will be shown on it. I would think the injection diagram should be ample for tracing this fault.

[JamesQB]

Hi, thanks for supplying those diagrams.

Checks done and the 12V supply to pin C3 of the ECU is present. Grounds have continuity to battery negative. CAN high and low are 2.5V on the ECU connector. Don’t have a scope to check waveforms.

Not sure what to do now?

[JamesQB]

The most likely culprits would be the under bonnet fusebox (BSM). This incorporates the main relay that supplies the ECU with power.

I can’t see any relay involved in supplying power to the ECU. Am I missing something?

[wheeler]

Have you checked pin M2 on the 48 way brown connector of the ECU? This is fed from the 1st relay inside the under bonnet fusebox.

[JamesQB]

Hi,

M2 is now checked and there is no voltage present. We're having trouble finding the relay which is associated with this feed.

This is the underbonnet fusebox, but there aren't any relays visible.

There is a dual relay, Omron 240107, secured to the body and connected to the wiring loom. Google shows it as a fuel pump relay, is it to do with this?

Thanks

[wheeler]

The relays are integral to the under bonnet fusebox, they are not designed to be replaced separately however you can if your handy with a soldering iron. You need to split the BSM open to see the relays but they are soldered onto the board.

[wheeler]

That type of ‘double’ relay is also used a an ABS relay on some models

[JamesQB]

Big thanks to Wheeler for your valuable help which allowed us to get the car running again.

To recap: Pin M2 on the 48-way brown connector of the ECU turned out to be missing its 12V supply.

The culprit: The relay responsible for that 12V supply wasn't being energised. The relay should be switched on by a ground being supplied to its coil from the ECU. This ground wasn't getting to the relay's coil due to a series diode that was open-circuit. The diode isn't shown on the diagrams.

Due to the difficulty removing the PCB, a replacement diode was soldered to the underside which has fully restored function.

Below is a photo I took of the BSM B3 with part number: 9657608780. I have drawn the PCB connections on. Maybe this will help someone else in the future.

BSM B3 9657608780

[wheeler]

Great result, i wonder how many of these units get replaced when really all they need as a diode costing a few pence?

[Markieboy7]

Thanks for the above, really useful information. Does anyone know where pin E1 goes? We don’t seem to have a ground connection to this pin so the relay won’t open on the BSM. Thanks