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FIXITMAN, Master Technician
Category: Subaru
Satisfied Customers: 17329
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Subaru Forester: I have a 2009 forester. Problem started with

Customer Question

I have a 2009 forester. Problem started with low tire pressure light, followed a few days later by check engine an others. Have take to a local garage twice, and Subaru garage once. In every case they reset the codes and say there is no problem (even after driving around town), but it comes back (the last 2 times the tire pressure light came back within 10 minutes at highway speed.) The other lights usually follow within a day or two. The last time I was told, if it is still running OK, keep driving, which I did until nearly every warning light on the dash came on, acceleration became a problem, and the speedometer starting to not work (setting at either 0 mph or pegged high, and occasionally registering true speed for a few seconds. (The speedometer failures seemed to correspond with the brake and traction control lights cycling on / off. I took it to the dealer, they reset the codes (P0500, C0057) and said they couldn't find anything wrong again, but think it "might" be VDCCM
Submitted: 1 year ago.
Category: Subaru
Expert:  FIXITMAN replied 1 year ago.
Hello, my name is***** for the question. It sounds like you have a voltage issue. This can be caused by a bad battery, a failing alternator or a bad battery terminal. If the voltage in the system gets low enough the car will act like this. If all of these test fine then the next most common I have seen is the ignition switch. I have changed it on this same car for very similar issues. I hope this helps. Let me know if you need anything else.
Customer: replied 1 year ago.
Thanks. I don't believe it to be the battery, which we changed out when it was thought to be the problem, or the alternator, which the local garage checked and said was fine.
Customer: replied 1 year ago.
Does it make sense to be the ignition switch when the initial problem (low tire pressure) seems to only come in after a drive t highway speed? (After clear the codes, both the local garage and the Subaru garage drove the car around town without a problem. The other problems follow after a period of time (usually a couple of days). The speedometer issue (either sitting at 0 or sitting at at140+ and not moving, and only occasionally and for a few seconds registering actual speed, with the odometer not adding miles during the times the speedometer was not working),was something the Subaru garage said they had never seen before, but did not come back (yet) after they cleared the codes.
Customer: replied 1 year ago.
As a note, the local garage (Mieinieke) also thinks it may be a voltage issue, but hasn't been able to figure it out, because the alternator seems to be OK and we've replaced the battery. They did say that one of the O2 sensors was responding sluggish but seems to be doing better after they "blew it out." The computer module the Subaru garage suggested scares me, because they are in no way sure, but thought it "might" be the problem, and that is a $750 part.
Expert:  FIXITMAN replied 1 year ago.
The reason I mention the switch is that it can develop high resistance when it gets hot and this will occur. It may be the module but all of these other items must be checked first. Was the module ground connections checked?
Customer: replied 1 year ago.
The Subaru garage said there were no loose connections to the module. I would assume that would mean grounds as well, but I didn't ask specifically.
Expert:  FIXITMAN replied 1 year ago.
I would make sure as they may have just checked the connections. The grounds are not necessarily by the module.