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Guest Message by DevFuse

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'97 Legacy Powertrain Control Module?

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4 replies to this topic

#1 LisaG


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Posted 22 July 2004 - 10:43 AM


We've been having a problem with my Subaru sputtering and stalling off and on now. Have replaced the Mass Air Flow Sensor twice now (codes were showing it was bad), to no avail. Took it to the Subaru dealer and they found code P0102 for Mass Air Flow Low Input. Checked and cleaned connection at Powtertrain control module and sent us on our merry way. Thought we were good to go - drove it about 20 minutes, 3 hours later went to drive it back home and the bleeping thing starts doing it's whole stall song and dance again. Subaru said if the problem returned then the Powertrain Control Module may need to be replaced to the tune of $685. We've already spent $500 between diagnostics and MAS..........

Questions: How likely is it that the Powertrain Control Module is the problem?

How hard is it to replace (I've got a mechanically savvy hubby fortunately)?

Can you purchase one on ebay or through a wrecking agency, or is it only worth buying new?



#2 LisaG


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Posted 23 July 2004 - 11:21 AM

Anybody out there?? P l e a s e H e l p :banghead:

#3 RallyKeith


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Posted 23 July 2004 - 11:55 AM

Anybody out there?? P l e a s e H e l p :banghead:

Well see, I've never heard of this Power Control Module and that's why I've yet to offer any advice. As far as I know all of the engine's functions are controlled by the ECU. The only other control modules in the car would be one for the Transmission and one for the airbags. So my first suggestion is to talk to the dealership and find out just what they are really talking about, but from the sounds of it they mean the ECU.

Now, as far as the ECU goes, I would highly doubt that it would be a problem unless there are wires shorting out somewhere. As far as replacing, they are pretty easy to replace, and can be had used for around $200. www.car-parts.com is a good place to locate used parts all across the country.

Also, do you kow what code it showed the times you had the Mass air flow sensor(MAF) replaced? As far as I know there is no code that means the sensor is bad. It will either say the signal from it is too low or too high. This can be caused by many things. If the code it gave was for a low signal that means it is not sensing as much air flow as it thinks it should be seeing for the RPM the engine is spinning. If that is the case you could have a hose somewhere after the MAF that is letting in air. That's the kind of thing that while sitting still in a garage might not act up, but on the road going over bumps and flexing with the load of the engine would act up.

I hope this helps somewhat.


#4 jcniest5


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Posted 24 July 2004 - 12:22 AM

The ECU (and also the TCU), which can be purchased at this Junk Yard for roughly $14.00 (in the Twin Cities, Rosemount, specifically and it's called U Pull R Parts) assuming they have it. Sometimes they do, sometimes they don't. Once you have it, it's very easy to replace. Just a matter of disconnecting the wire connectors, unbolting the module and take it out and put the new one in. Ten minutes max.

#5 Cougar


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Posted 25 July 2004 - 10:10 AM


From the things that you stated it seems to me there still may be a wiring connection problem to the MAF sensor. After the shop worked on the connections the car ran ok for awhile. I would check to make sure the wiring between the sensor and the ECU were definetly good before changing the ECU out. Checking the resistance of the wire connections out between the two modules would be my first check. Monitoring the voltage from the MAF at the input to the ECU will tell you if it is really correct also. If the signal voltage is low there then you know that there is still a wiring problem. Since you have changed the MAF twice that can be ruled out as a possible problem. Checking the voltage input to the MAF would be good to do also. Having a low input may cause a low output to the ECU. I think that would cause another code to be sent to the ECU possibly, but I'm not sure on that.

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