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Subaru Legacy, Subaru Outback, Wagon
#6270 of 8644 hum when engine turned off (2002 Legacy L Wagon)
Jul 23, 2006 (7:53 pm)
I have an automatic transmission 2002 Subaru Legacy L Wagon,in good shape, under 50,000 miles. Recently it has been making an odd humming sound when I shut the engine off. This is a low pitched sound, steady (not vibrating or oscillating), and it can last up to 45 seconds or so with the car shut off and key taken out, until it eventually fades off to silence. I've never heard anything like this before it started a week or so ago, and I haven't taken it for service or anything--I figured I'd start here. Anyone have any ideas?
#6271 of 8644 Re: 2001 outback h6 vdc [dondaly]
Jul 23, 2006 (10:18 pm)
The service manual for 2000-2003 lists the code as follows:
P0171 : Fuel trim malfunction (A/F too lean) : <Ref. to EN(H4)-155 DTC P0171 — FUEL TRIM MALFUNCTION (A/F TOO LEAN) —, Diagnostic Procedure with Diagnostic Trouble Code (DTC) for MT Vehicles.>
There is no P0174 code in the manual or the H6 supplement.
#6272 of 8644 Re: hum when engine turned off (2002 Legacy L Wagon) [rdh3t]
Jul 24, 2006 (9:28 am)
Sounds like the radiator fan. It started recently because the weather has warmed up, and the engine and cooling system is running a bit hotter as a result. The car wants to cool down the antifreeze to a acceptable level before it shuts off the fan.
If this is the case, it is normal and many cars do this.
#6273 of 8644 Re: hum when engine turned off (2002 Legacy L Wagon) [tkanic]
Jul 24, 2006 (10:12 am)
Doesn't it need accessory power to do this? If I take my key out, I lose accessory power on my 00 outback.
#6274 of 8644 Re: hum when engine turned off (2002 Legacy L Wagon) [rangner]
Jul 24, 2006 (12:01 pm)
No, that's the whole idea. The fan runs with no key and no-one around if it has to. That is why you will frequently find an under-hood sticker warning that the fan can start at any time. Residual heat from the engine after shut-off still enters the cooling system, but your pump is not running any more, so the fan must turn on to avoid overpressure and excess heat.
#6275 of 8644 Re: pinging [dsain]
Jul 24, 2006 (12:11 pm)
I think you will get a code for a defective knock sensor, as I did. I ordered one over the internet for about 1/4 of the Subaru price and while I was waiting for it to arrive I drove 1500 km across three mountain ranges with the light on from time to time. I didn't notice any pinging, but took care to not labour the engine (5 speed). I used regular gas as always but would have switched to premium if I heard pinging. The sensor is right on top of the engine and took about 10 minutes to replace.
#6276 of 8644 Re: Door Lock Blues [ebony5]
Jul 24, 2006 (1:02 pm)
Same here, though this year I have only had the "problem" crop up twice. The real annoyance with it is the rear hatch, as there is no latch mechanism or anything to open it from the inside (oddly, I find myself needing to do this fairly often since the hydraulics do not work on the door any longer)and the key lock on the outside argues with me every time I go to use it.
I hear that the problem is the switch mechanism in the driver's door and the fix is to access it and adjust it (it wears with time/use). So far, if I really want to open all the doors from the driver, I just repeat the lock/unlock motion repeatedly until it works. That is the stubborn man's solution. Darn old cars, anyway.
#6277 of 8644 Re: Pinging [mrk610]
Jul 24, 2006 (1:08 pm)
How do you run your Seafoam? Just through the gas? I hear there is a "deep clean" you can do with it by allowing it to be sucked through the vacuum system.... anyone know if there is merit in that?
#6278 of 8644 Re: pinging [goosegog]
Jul 24, 2006 (1:33 pm)
You can experience problems related to the sensor if it is not being fully responsive. Usually the CEL will only trigger if the sensor stops sending feedback (either intermittently or altogether). That said though, gummed up injectors/valves can cause pinging that the knock sensor will not correct and it does not mean that the sensor is going bad. *shrugs*
#6279 of 8644 Re: pinging [xwesx]
Jul 24, 2006 (4:48 pm)
I wonder if any good cleaning additive would help. I'm thinking no, I recall a somewhat recent post where someone tried that with no luck.