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Knock Sensor Test Procedure (2.5liter)


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6 replies to this topic

#1 Phillip

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Posted 08 September 2003 - 01:52 PM

Does anyone know the test procedure for checking the Knock Sensor on a 1999 Outback 2.5 liter? I pulled (and cleared) codes several times; each time the code for a problem in the Knock Sensor circuit returns. My Motors Manual says the knock sensor ohm reading should be between 400 - 700 (mine is 556). Motors procedure for checking resistance in the wiring refers me to terminal #30 at the ECM; unfortunately for me, there is no wire in terminal #30 at the ECM. With the code cleared, the car runs great, but once the check engine light illumintes (10 - 15 miles after clearing the code), the engine power drops significantly. I suspect the computer goes into 'limp-in' mode, not permitting ignition advance. Any advise will be greatly appreciated. Thanks

#2 Cougar

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Posted 08 September 2003 - 02:25 PM

Somehow the wire from the sensor has to get back to the ECU. Have you tried to locate the wire by looking at the wire color at the sensor and see if matches any of them at the ECU end and then do a continuity check on any that match? If you can't find a match you could try them all and it wouldn't take too much time to run through them.

Unless the sensor is intermitant it sounds like it is ok so I would say you have a connection problem somehow. If you can't find the wire I would purchase a factory service manual that covered the wiring for your car. These are 'priceless' in my opinion. If it saves you a shop repair it would pay for itself on the first repair.

#3 North Ursalia

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Posted 08 September 2003 - 02:31 PM

The knock sensor on your car is notorious for going bad- we replace them all the time (it's a 22060AA070 BTW). In fact, I *think* Subaru just redesigned it- there was about a 2 week span where they wouldn't ship any of them (which is why I think they redesigned them) and we're just now getting them back in. Borrow one from someone (it's found in the 2.5 Imprezas, Legacys, and Foresters) for 15 minutes- they're incredibly easy to change out.

#4 Phillip

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Posted 08 September 2003 - 06:54 PM

Your help is sincerely appreciated. I'll install a new knock sensor this weekend and let you know how it worked out. Thanks again!

#5 billrigsby

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Posted 08 September 2003 - 07:15 PM

According to my handy-dandy 1999 Impreza CD ROM
The 2.5 (Forester) knock sensor is a Blue/Red wire
and goes to pin 4 of the ECU.

Not sure if yours is the same :rolleyes:


Bill

#6 North Ursalia

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Posted 08 September 2003 - 07:16 PM

You are most welcome... we're all here to help each other out, and at least for the newer cars I know my stuff :D. I'll figure out these old skool cars I owned 2 of (and knew virtually nothing about) and now own 1 of (the BRAT) yet :D!

#7 aaronka

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Posted 03 October 2003 - 01:32 PM

I had a bad knock sensor diagnosed on my 2000 OBW recently and they said it was backordered. They wanted $95 for it but I found it at www.subaruparts.com for about $70 including shipping. They also wanted an hours worth of labor to install it. Glad I had didn't have them do the work. They still charged me $78 for the diagnosis!!

So these are pretty easy to change? How do I know if I am buying the latest design (since it sounds like they keep getting updated)?




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