Please help! P0131 and P0300 in my 2002 Z28. I have already used the search button.
07-19-2014, 10:16 AM
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Please help! P0131 and P0300 in my 2002 Z28. I have already used the search button. I am the original owner of a 2002 Z28 with external bolt ons only. The SES light came on last night during a pass at the dragstrip. Afterwards, I connected Autotap and saw this:
Confirmed Diagnostic Trouble Codes:
Code: Description:
P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1
P0300 Random/Multiple Cylinder Misfire Detected
--------: FREEZE FRAME DATA :--------
Generated by DTC code: P0300
Fuel System Status Bank 1: CL-1
Calculated Engine Load: 7.8 %
Engine Coolant Temperature: 183 °F
Short Term Fuel Trim Bank 1: 56.3 %
Long Term Fuel Trim Bank 1: 0 %
Short Term Fuel Trim Bank 2: -18 %
Long Term Fuel Trim Bank 2: 0 %
Manifold Absolute Pressure (MAP): 8.3 in Hg
Engine Speed: 1959 RPM
Vehicle Speed: 57 MPH
Mass Air Flow Rate: 2.871 lb/min
Throttle Position Angle: 6.3 %
----------------------------------------------------
Before I threw the code, the Z28 had rough idle in a few occasions during the previous two weeks and it would be noticeable only when the engine was hot. Also, these events started happening after I got their fuel injection cleaning and the fuel filter replaced at the local Midas. The tech had replaced a rubber elbow around the intake area, because there was a hole in it causing the area to whistle. He said he found a sturdier substitute to replace it. Maybe a vacuum leak still exists in that area? I will bring the Z28 back to the shop so that they can do a thorough diagnosis.
What else can cause these two codes? I will suggest the following to Midas:
- that they check to see if the wires to the O2 sensors are still in good condition (the O2 sensors themselves are new and have less than 20,000 miles);
- that the catalytic converters (high flow cats from the Kooks y-pipe) are still in good condition;
- and determine if they replaced the fuel filter correctly.
What else? Thank you in advance for any input.
Confirmed Diagnostic Trouble Codes:
Code: Description:
P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1
P0300 Random/Multiple Cylinder Misfire Detected
--------: FREEZE FRAME DATA :--------
Generated by DTC code: P0300
Fuel System Status Bank 1: CL-1
Calculated Engine Load: 7.8 %
Engine Coolant Temperature: 183 °F
Short Term Fuel Trim Bank 1: 56.3 %
Long Term Fuel Trim Bank 1: 0 %
Short Term Fuel Trim Bank 2: -18 %
Long Term Fuel Trim Bank 2: 0 %
Manifold Absolute Pressure (MAP): 8.3 in Hg
Engine Speed: 1959 RPM
Vehicle Speed: 57 MPH
Mass Air Flow Rate: 2.871 lb/min
Throttle Position Angle: 6.3 %
----------------------------------------------------
Before I threw the code, the Z28 had rough idle in a few occasions during the previous two weeks and it would be noticeable only when the engine was hot. Also, these events started happening after I got their fuel injection cleaning and the fuel filter replaced at the local Midas. The tech had replaced a rubber elbow around the intake area, because there was a hole in it causing the area to whistle. He said he found a sturdier substitute to replace it. Maybe a vacuum leak still exists in that area? I will bring the Z28 back to the shop so that they can do a thorough diagnosis.
What else can cause these two codes? I will suggest the following to Midas:
- that they check to see if the wires to the O2 sensors are still in good condition (the O2 sensors themselves are new and have less than 20,000 miles);
- that the catalytic converters (high flow cats from the Kooks y-pipe) are still in good condition;
- and determine if they replaced the fuel filter correctly.
What else? Thank you in advance for any input.
Last edited by damon_Z; 07-19-2014 at 10:24 AM.
07-20-2014, 08:49 AM
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Sounds like a failing o2 sensor, the same thing happened to me when one failed on my car. If you want to confirm the failure switch the front o2 sensors clear your codes and see if it throws the o2 sensor code for the other bank.
07-20-2014, 10:35 AM
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I have considered this as a possibility, but all of my O2 sensors were replaced in 2011. Nevertheless, the shop will determine if that is the cause. If it is the cause, then the next question is: what made the O2 sensor go out so soon? I did get bad exhaust rattle that night. Maybe it was bad enough to damage it?