Seat leon stereo not working

[Leondj]

I recently purchased a 2009 Seat Leon. I decided to remove the OEM Stereo and try out the Android HU I removed from my previous car. Unfortunately it didn't work. Not only that but when I reconnected the OEM stereo, it didn't work either.
The pin connections are shown in the photo below'
When I tested pin 5 I got 2V with ignition on or off. On pin 6 I got 12V with the ignition off. But only 2V with the ignition on.
Is there an easy repair without having to take power from another source (fusebox).
Gratefully appreciate any help you can give.

 

[Diver300]

You do realise that the connector in the photo is the mirror image of the diagram, don’t you?

Check the ground is connected to the car body. You can check to the outer of the cigar lighter.

The CANbus wires will often be at about 2V.

 

[Leondj]

You do realise that the connector in the photo is the mirror image of the diagram, don’t you?

Check the ground is connected to the car body. You can check to the outer of the cigar lighter.

The CANbus wires will often be at about 2V.

Thanks for your reply. Yes I do realise that. Pins 3 & 4 are the ones marked U+ on the diagram. There's no voltage at these pins, so don't know what they're used for. I did at first use pin 8 when checking voltages. Results were the same when using a different earth source.

So if CANbus is typically 2V. Where would the radio have been getting it's permanent & switched live from (when working)?

Is it normal for CAN- to be 12V with ignition off?

 

[Diver300]

It’s not normal for the CAN wires to be at 12 V.

The CAN wires will be in one of three states. When dormant they will be in the range 2 - 3 V and they will be the same voltage. When active CAN-H will be about 2 V higher than CAN-L. However when you measure with a voltmeter you see the average voltage. CAN data is generally about half active (logic 0) and half dormant (logic 1) so on average the difference between CAN-H and CAN-L will be about 1 V at most, and less if there is little data traffic on the CAN bus.

When the CAN bus goes to sleep and all traffic stops, there will be the same voltage on CAN-H and CAN-L. The various modules go into low power mode and both CAN voltages may change. There is no “correct” voltage at that time, but both must be the same.

The CAN bus going to sleep is not the same as ignition off. Most CAN buses are awake from when the car is unlocked until a few minutes after the engine stops. Some CAN buses stay on for other reasons, such as when an EV is charging.

The other possibility is that those two connections on your car have nothing to do with CAN at all.

 

[Leondj]

Thank you for that explanation. Unfortunately that doesn't solve my problem. I removed the 4 wires from the power block on my Android HU and tried connecting them to the quadlock in various configurations but to no avail. Looks like my best and only solution will be to piggy back of the relevant fuses (should have a couple of those leads). My main problem there will be figuring out which wire is switched live. The Connects2 adapter has black, yellow, green & white. I'm assuming yellow is still permanent live.

 

[Diver300]

It’s possible that the car has no switched live connection to the radio. The CANbus will have all the information needed so that the OEM radio knows when it should turn on.

There my be other information sent over the CANbus, such as remote volume controls.

 

[ZipZapOuch]

It's also possible that the replacement radio caused a dead short to ground if the wires were not correctly assigned vs original radio. Check the fuse for the radio (best case). Worst case, the connection to other peripherals was burned out before the fuse blew.

 

[Leondj]

It's also possible that the replacement radio caused a dead short to ground if the wires were not correctly assigned vs original radio. Check the fuse for the radio (best case). Worst case, the connection to other peripherals was burned out before the fuse blew.

I did check the radio fuses and they are fine. I did check the car fuses before swapping the radio's. As I was getting power I assumed they were ok. Will check them again. Would a short explain why I'm getting 12 with ignition off?

 

[Nigel Goodwin]

I did check the radio fuses and they are fine. I did check the car fuses before swapping the radio's. As I was getting power I assumed they were ok. Will check them again. Would a short explain why I'm getting 12 with ignition off?

No, but car radios commonly have a permanent source of power (to maintain memories etc.), as well as a switched one.

This is why if you disconnect the car battery you have to enter the radio security code when you reconnect it.

 

[aliarifat794]

Use a multimeter to test the voltage directly at the power supply wires for the stereo unit. If you're getting inconsistent voltage readings, there may be a problem with the wiring or the power supply itself.

 

[Leondj]

Use a multimeter to test the voltage directly at the power supply wires for the stereo unit. If you're getting inconsistent voltage readings, there may be a problem with the wiring or the power supply itself.

That's where I was testing (at the quadlock plug).