Engine Eec Fault Codes

Discussion in '1994 - 1995 Specific Tech' started by hssnpny, Sep 8, 2012.


  1. hssnpny

    hssnpny Member

    Joined:
    May 30, 2002
    Messages:
    45
    Likes Received:
    0
    Trophy Points:
    7
    So the car's been running fine. Comes time for the Calif smog test. The car's been passing as-is for the last 10-12 years, but now they won't test it due to the BBK H-Pipe since it only has 2 cats, compared to the factory 4 cats. So I take the car to a local muffler shop to have my old factory H-Pipe put back on.

    When I first take the car out, it doesn't feel right, way low on power, sluggish, surges at idle. After about 15 minutes I'm climbing a hill to get home and it just doesn't want to go at all. I'm downshifting just trying to keep it moving, any right pedel and it just loses all power. Somewhere in here the CEL comes on. It doesn't stall, but any more than the slightest bit of gas and it won't move. I take 3 miles of side streets in 1st and 2nd and a lot of clutch to get home. Hot and ****ed.

    I hook up the code reader and get the following:
    172 - Heated oxygen sensor fault/lean bank #1
    173- Heated exhaust gas oxygen sensor fault/rich bank #1
    176 - Heated exhaust gas oxygen sensor fault/lean bank #2
    556 - Fuel pump relay primary circuit fault
    456 - This code wasn't in my book - google says "Insufficient RPM decrease during test", but I was doing an engine off code read, so not sure about that one.

    Any thoughts on the best place to start to figure this out? Don't know what 12 years of sitting in my garage might have done to the cats on the factory H-Pipe. The O2s have been fine up until now.

    Thanks.
  2. g96v6-250k

    g96v6-250k Member

    Joined:
    Aug 15, 2012
    Messages:
    91
    Likes Received:
    1
    Trophy Points:
    8
    so these 02 sensors were in-use installed in your BBK pipes and were apparently working? now they are moved over to your factory h pipe and wont work? i would think sitting 12 years only oxidized the carbon and made them like new. you can bench test 02 sensor with a torch and a volt meter. do some research on the code 556, that sounds like a problem that can mess with fuel delivery.
  3. hssnpny

    hssnpny Member

    Joined:
    May 30, 2002
    Messages:
    45
    Likes Received:
    0
    Trophy Points:
    7
    yes, the same o2 sensors have been working fine in the BBK exhaust for 12 years. Now that they're back in the factory pipe I'm getting codes. It seems unlikely that both would go bad right now, but I have to start somewhere I guess.
  4. toyman

    toyman SN Certified Technician

    Joined:
    Jul 20, 2007
    Messages:
    1,818
    Likes Received:
    33
    Trophy Points:
    49
    Are you certain they are plugged in? Here's the best way to test them

Share This Page