S40: 2002 S40 1.8 petrol automatic stalling after starting

[Ltom]

Gatos yes I did that. It's properly adjusted but doesn't help. I tried opening it more but to prevent the car stalling the throttle needs to be about 1/4 open.

I got a code reader today and got the following codes twice (before and after reset):

P0138 9 Oxygen sensor high voltge (Bank 1, sensor 2)
P0602 Control Module Programming Error
P1500 Vehicle Speed Sensor Intermittent

Could a lambda sensor cause this issue? If does anyone know whether Bank 1 Sensor 2 is the front or rear lambda sensor?

[magnuz]

Oxygen sensor 2 is usually the one after the cat, normally,it's only job is to monitor the exhaust gas after the cat to check the cat is working properly.
It doesn't normally make any adjustments, so doesn't usually cause running problems, but to throw up the code, it's probably faulty anyway ? .

The other two fault codes are probably related to control module issues on the auto transmission ?

[Ltom]

Thanks for the reply Magnuz. So it sounds like the oxygen sensor probably isn't causing the stalling.

Do you know where the speed sensor is on the auto transmission? The rpm gauge works fine, does that come from another sensor?

[magnuz]

I'm not very familiar with the auto box versions, but have a look around the gearbox for any sensors or modules, etc. check the wiring & connectors to any sensors.
Is the engine stalling in neutral, or only when drive is selected ?

Vehicle speed sensor, ...going by it's name, may be more to do with vehicle speed, rather than engine speed ?

[Ltom]

So I had a poke around, unplugged and checked connection on a few sensors connected to the engine. Then I cleared the codes and the engine started fine.

I took it on a test drive and the car performed much better (smooth shifts), started without stalling, and the error codes didn't re-appear.

Still a mystery, I'll give it a few days and see if/when the light comes back on and what the codes are. Because of the seemingly random nature of the symptoms I think it's electronic/electrical. Either a faulty sensor, sensor connection, or ECU fault. Which one exactly I'll keep investigating.

[Ltom]

UPDATE

I narrowed it down to the MAF in the end. I replaced it with a used Volvo one. If someone is reading this because they have the same problem then this is exactly what I did.

Buy a used volvo MAF off fleabay (I bought the whole airbox for £15).
You need an OBDII reader. I used a generic one that looks like this one: https://www.amazon.co.uk/Scanner-Ada...dp/B07883V8KC/
You also need an app (like Torque pro) to reset the codes through the reader.

Replace the MAF with the new one. Plug in the OBD2 reader. The reader will only work properly when the ignition is in the ON position (the most clockwise position before it cranks). You can't reset the codes properly if the engine is running. Use an app like Torque pro to reset the codes and that should fix it.