2007 S40: Steering Failure Service Requires to Steering Failure Stop Safely

[theWIFES_S70]

The S40 has been a beautifully reliable vehicle. But alas, an electrical gremlin has shown its head...

Got this one today after work... Drove about 40 mins and parked on the street.

IMG-20231113-WA0009.jpeg (90.13 KiB) Viewed 974 times

Car would not crank. Looked up on Youtube for a solution and stumbled upon the following video.

https://youtu.be/BEt8oxXTqxM?si=Nk1jGUbwBGAQDo42

It appear that this immobilizer on the P1s is a doozy. Fortunately, I don't think this is a steering wheel problem. What I did try from this video was disconnecting the battery and resetting the error message. That helped me get to my parents and eat dinner and then get home a few hours after.

As soon as I shut the car off at home, I got this error message. So it seems a little more serious than an electrical gremlin.

PXL_20231114_020915195.jpg (137.77 KiB) Viewed 974 times

Guess, I'm doing an alternator swap this weekend... Just spent a bit of time reading through threads like these:
https://volvoforums.com/forum/volvo-s40 ... nt-65797/

Kinda sucks living NO WHERE near any independent Volvo shops.

[RobsS40]

'06 S40 here. I've had several similar problems. I'm very unhappy about the immobilizer. Car should not shut itself down due to CAN bus communication failure. Although I think I figured it out and fixed it, I might go back to pre-1980 cars (including my 1929 Model A Ford!).

But anyway, beside my infernal car wrenching habit, I'm an EE. I studied the CAN bus a bit. I don't have the proper electronic diagnostic tools, but I followed my gut instincts which were based on some facts. I kept getting several CAN bus problems, error codes, etc. Very difficult to reset EPS (Electric Power Steering) faults. I suspected the CAN bus wiring wasn't done right, and one day a couple of months ago I tore into it.

CAN bus rules are that it's 1) twisted pair, 2) a bus termination resistor at each end of the bus (typically 120 ohms at each end), and 3) taps, or "stubs", are no more than 12". When they built my harness they tapped into the CAN bus somewhere around the passenger side engine mount, then ran the stub- single pair- down to the EPS. That's a no-no. So I did some spicing and ran the twisted pair down close to the EPS, less than 12", then ran twisted pair back up to the rest of the harness. I soldered, heat-shrink splices.

So far, no CAN bus errors. Able to reset EPS every time, but it hasn't needed it any more. Yay!

I didn't tear into the rest of the harness to see if they violated CAN bus rules anywhere else. I kind of doubt it due to the physical layout and routing. And again, it's working completely well now.

Not sure if you're up for that level of work, but let me know what you think.