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  • #1

    Failed emissions 2 codes

    My 96 TA failed PA emissions the other day. The shop didn't have time to diagnos the codes so I thought I would ask some real experts.
    Codes are 0400 and 0420
    400 is the EGR flow
    420 is Catalyst system efficiency below threshold bank 1

    The only test I was able to do myself so far was to push on the EGR valve, and the eng ran rough as it was supposed to.

    Does the combination of these two codes point to a specific problem?

    Thanks for any input.

    Ryan
    96 Trans Am WS6 M6, K&N Filter, BBK Headers, Spec Stage II clutch, 180 Thermostat, MadZ28 tune... Best 1/4 13.76@103.7
    Tags: None
  • #2
    Ryan, I can't help you with your problem, but off topic: where in Hbg are you? I lived there for years when I was still living at my moms. live in Carlisle now, work in Middletown.
    Dave M
    Life, liberty, and the pursuit of all who threaten it!


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    • #3
      I believe the "400 is the EGR flow" is the same thing mine did. I have a 95 so it was a different code. I think it was 32 but not sure. I took it in and the dealer flushed the EGR pipe. They used some machine that connected to both ends or something. I didn't see it so I'm not sure. They also de-carbon-ed the EGR valve. He said LT1 motors are notorious for this. It has not thrown the code since then and it has been over a year so whatever they did worked.
      2002 Electron Blue Vette, 1SC, FE3/Z51, G92 3.15 gears, 308.9 RWHP 321.7 RWTQ (before any mods), SLP headers, Z06 exhaust, MSD Ignition Wires, AC Delco Iridium Spark Plugs, 160 t-stat, lots of ECM tuning

      1995 Z28, many mods, SOLD

      A proud member of the "F-Body Dirty Dozen"

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      • #4
        Did you fail a check only because there were codes present in the PCM, or did you also flunk the acutal emissions test?

        You might want to check with a (ohhhh, noooooo) dealer. I'm pretty sure there was a recall for the EGR valves in the OBD-II (96/97) cars. There was a problem with the valves not flowing enough to satisfy the diagnostic test, which looks for a change in MAP. If there was a recall, you might get a free replacement.

        On the P0420, low efficiency on the cat on bank 1, the "after-cat" O2 sensor on the drivers side is indicating that the catalytic convertor is not operating at the required efficiency.... obviously a cause for increased emissions. Could be a failing cat, or is could be a failing O2 sensor.
        Fred

        381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC engine management - 8 LS1 coils - 58mm TB - 78# injectors - 300-shot dry nitrous - TH400 - Gear Vendor O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motor

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        • #5
          Thanks for the input guys. I will check on the recall for the EGR valve. As far as the failed emissions, I think it was just due to the code but I am not sure.

          Dave, I live in Lewisberry exit 36 off I83. I see you have a 97 WS6. NICE! When it gets nice around here again and I get mine running right I am anxious to get it to a drag strip to see what she'll run. If your interested in that let me know. My email is Stackpra@hotmail.com

          Ryan
          96 Trans Am WS6 M6, K&N Filter, BBK Headers, Spec Stage II clutch, 180 Thermostat, MadZ28 tune... Best 1/4 13.76@103.7

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