Paulster 2 Petecon & Ben--- etc

A friend has been trying to help me with this 02 Forester. We have an OTC, EVOLE scan tool that we ran an all systems scan. What should I look for with the OTC, EVOLVE plate form or what scan mode. Have the tool but am not an expert with it by any means. What are the parameters that I should look for. Only code we have pulled so far is the P0328 code, knock sensor. Cleaned block and grounding end of knock sensor. Check engine light has gone off but comes on occasionally for a while then goes back off. ohms were 455 when I checked it. Can not grasp this no power going up hills. Can someone give me another starting point

  • 1
    do a WOT run through second gear to third gear on a hill. log ignition timing, fuel trims, rpm, map baro, fuel loop status, injector pulse width and all the afr/o2 sensors. iirc these older subarus have a low data rate and to get a meaningful log you're probably going to have to do several runs with only a few pids at a time. try to be consistent run to run. – Ben Jul 7 '17 at 20:41

To me the P0328 makes a ton of sense.

This web page states a P0328 code can be caused by:

  • Faulty knock sensor 1, bank 1
  • Open or short in knock sensor circuit wiring
  • Failed ECU
  • Wrong octane fuel or lean air fuel ration
  • Engine is overheating
  • Low fuel pressure

One of the major symptoms of this (other than the CEL) is a loss of power. If the knock sensor is sending back erroneous information and the ECU detects this, it will do what it can to protect the engine. One of the ways of doing this is to pull ignition timing, which drastically reduces engine power.

To see what the issue really is, follow the steps provided on the website: How does a mechanic diagnose the P0328 code?

  • Uses a scan tool hooked up into the DLC port of the vehicle and checks for any codes present along with any freeze frame data associated with the codes
  • Clears the codes and a test drives the vehicle to duplicate the symptoms and code
  • Listens for engine knocking
  • Performs a visual inspection, looking for any faults
  • Checks the cooling system and engine for any faults
  • Check the fuel octane and fuel system if the engine is knocking
  • Uses the scan tool to monitor the knock sensor voltage for changes if engine isn't knocking
  • Uses a scan tool to check the engine coolant temperature and fuel pressures
  • Tests the ECU, each vehicle has it's own testing procedure for the ECU

I'm not positive of what exactly your scan tool is capable of, but would suggest reading the manual on it and/or looking online at the product's website (if there is one). Big to-dos here are first to ensure you are using the correct octane fuel. I'll assume this is a turbo-charged Subie, which to me would indicate you'd need premium fuel (at least 91 Octane - R+M/2 scale). Next is to actually listen for knocking in the engine. If you don't hear any, it may very well be the sensor has gone bad. Double check the wiring to ensure it's good (no obvious frays, etc).

  • Just from experience, knock sensor circuit codes on Subarus won't pull timing and other than the light being on there are generally no drivability complaints. – Ben Jul 7 '17 at 20:37
  • @Ben - With the code and the loss of power, it does fit though. You could be right ... you do a lot more of this work than I do. – Pᴀᴜʟsᴛᴇʀ2 Jul 7 '17 at 21:35
  • yah, not saying it can't happen. just not from my experiences working on these. – Ben Jul 7 '17 at 22:11

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