My check engine light is on in my 2002 S40. I believe it was triggered during an especially cold day back in January, when it first appeared. Is there a way for me to get the codes without using a tool or taking it to a mechanic? My friend has an older Volvo wagon and he was able to pull the codes manually by reading a series of flashing lights under the hood. Is there any such way to do this with this vehicle?

Also, can anybody tell me where I can find the ECU fuses for this vehicle? I read elsewhere an easy way to clear the codes without even needing to disconnect the battery:

Pull the ECU fuses from under the hood. Turn ignition to three position (car will not start). Replace fuses. Start car..

But I'm not sure where I would find those fuses. I was told there are 2 different locations for fuses in the 2002 S40 - under the hood and under the passenger dashboard - Is this correct?

 

No there is not.

Just being cold isn't going to cause the check engine light to come on. You can try disconnecting the battery to clear them, but it will be back in all likelihood.

 

Thanks for the reply. Next question then - I know there's a socket under the driver's side to connect a tool to read the codes. Will this reader work:



Will this display all codes (including transmission, etc)?

And what about pulling out the ECU fuses to reset the codes? Where would I find the ECU fuses? I would prefer to do that as opposed to disconnecting the battery. And is this the same as ECS?

 

It would be better to disconnect the battery.

That code reader will likely only pull generic OBDII codes.

I don't know where the ECM fuses are off hand. Volvo doesn't use the term ECS.

 

I went through this too fiey24. I had 3 codes when I bought my 2003 S40. I made some repairs and wanted to clear the codes so I left the battery dicsconnected for 2 days. This did not clear any of the codes.

I bought the cheapest OBDII reader Amazon had, it was $18. It reads all of the generic OBDII codes and clears them easy enough. I have the infamous P0420 code, "Catalyst system below Efficiency Threshold (Bank1)". I clear it and it comes back at random, sometimes the next day or it might go 2 weeks. But I cannot just assume that that is what the CEL is, so everytime it comes on I have to immediatly check and clear the code. It would be very annoying to have to stop into Autozone every few days, and I'm sure they would tire of seeing me too.

So for me having a OBDII reader is a necessity. The one you linked to looks like a nice one, and that sale price is almost too good to pass up. If you get it can you report back if the live data function works on Volvos?

 

So then that model I linked to will read all transmission/engine codes, and clear the codes also? Does it do all that through the OBDII port under the driver's side dashboard, or do I have to plug it in under the hood for some codes?

I thought for sure just disconnecting the battery or pulling out the UCU fuses would reset the codes. That won't reset the check engine light code then?

 

Oh I see. I was checking my manual for the ECU fuses, and I noticed it doesn't list that term. It does list ECM and ECC. So I guess it's the ECM fuses then? There seem to be several different ECM fuses under both boxes. I was hoping pulling the fuses would reset the codes and at least that way I could see if they come back. But now I don't even know if unplugging the battery would clear the check engine light.

As far as that reader I linked to - so when you say it will only read generic codes, does that mean that it likely won't read any Volvo specific codes? I guess it wouldn't do much good then if it can't read engine codes, transmission, etc.

I don't really have the money to experiment with buying tools just to see if it will work without knowing beforehand. All I really want to do is clear the codes and get rid of the check engine light and see if it returns. If it's a real problem the light will come back on anyways I would imagine, and that's what I wanted to see.

 

ECM is what Volvo calls the ECU. (Engine Control Module). ECC is Electronic Climate Control.

 

I found this about error code reading on the S40:

"OBD II contains only emissions related diagnostic trouble codes (DTCs) and parameters. It cannot provide the comprehensive range of information available from the Volvo On-board diagnostics system. Volvo has its own diagnostic trouble code (DTC) designations that adhere to the in-house Volvo On-board Diagnostics protocol (called DII from model year 1999)."

The reader I linked to above is a U581 CAN/OBDII/EOBDII Memo Scanner. So then that reader would only read emissions related diagnostic trouble codes, and not advanced messages like transmission, etc.?

 

Yeah, most likely. Any cheap code reader is not going to have the function of a high end scanner or dealer level equipment. That basically applies to any OBDII car. OBDII is a standard that all manufacturers must follow, to allow basic emissions related faults to be diagnosed by independent shops. They can add their own proprietary information that cannot be read by these generic code readers.

 

Thanks again. Livens above mentioned he left his battery disconnected for 2 days and it still didn't clear the codes. But I've read elsewhere that doing that should clear away the check engine light and clear the codes. Has anybody had any luck with disconnecting the battery to clear away the check engine light? I'd really like to get this thing cleared so I can see if it returns.

 

I wasn't sure if disconnecting the battery will work. I don't use that method because I work at a dealer.

 

I just clear my codes with a generic OBD2 code reader. They are cheap and will tell you the generic OBD2 code when the check engine light is on. Now I also have the DiCE tool and VIDA software because I'm a DIY nut but normal folks won't need these.

Grab a cheap CAN BUS compliant OBD2 reader and you can use it on all your cars. It's a tool that lasts for a long time.