I had a check engine light come on and stopped by an Advanced Auto Parts store to get the codes. It's indicating that the system is running too rich and provided 2 codes: P0172 and P0175. My Vette is a 2002 Z06 and has just turned 8,000 miles and is all stock. Any ideas what the codes mean or what the problem would be? Interestingly (to me, anyway) the check engine light turned off after the scan and and has stayed off. Thanks!

 

Are you aware that it's not necessary to use an external scan device to retrieve the codes on a C5/Z06 Corvette?
You can retrieve the codes on the DIC. If the codes have a "C", they are current and may need immediate attention. If the codes have an "H", they are history and may not need any attention. You can also clear all of the codes from the DIC if that's your preference.
You can find the root cause of the codes with search in C5 Tech using the codes as keywords.
Or, you can retrieve the codes and look them up here...
http://www.stengel.net/diccodes.htm

 

Well, No. I am 'new' to the Corvette world. I just purchased this car several months ago so I'm still learning. I did a search after I posted and found some info that will be useful. Your info was also very helpful. I'm assuming that if I hit the owner's manual it will explain the code retrieval process? Thanks for the response!

 

http://corvetteclub.blogspot.com/200...ror-codes.html

 

Here's the descriptive portion of the diagnostic for the DTC out of the manual.

DTC P0172 or P0175

Circuit Description
The powertrain control module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during open and closed loop. During open loop the PCM determines fuel delivery based on sensor signals without oxygen sensor input. During closed loop, the oxygen sensor inputs are added and used by the PCM to calculate short and long term fuel trim fuel delivery adjustments. If the oxygen sensors indicate a lean condition, the fuel trim values will be above 0 percent. If the oxygen sensors indicate a rich condition, the fuel trim values will be below 0 percent. Short term fuel trim values change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. The fuel trim diagnostic will conduct a test to determine if a rich failure actually exists, or if excessive vapor from the evaporative emission (EVAP) canister is causing a rich condition. If the PCM detects an excessively rich condition, this DTC will set. If the PCM detects excessive vapor, then a pass is logged.

Conditions for Running the DTC

• DTCs P0101, P0103, P0108, P0135, P0137, P0141, P0200, P0300, P0410, P0420, P0430, P0440, P0442, P0443, P0446, P0449, P0506, P0507 or P1441 are not set.
  
• The engine coolant temperature (ECT) is between 75-115°C (167-239° F).
  
• The intake air temperature (IAT) is between -20 and +90°C (4-194°F).
  
• The manifold absolute pressure (MAP) is between 26-90 kPa (3.7-13 psi).
  
• The vehicle speed is less than 137 km/h (85 mph).
  
• The engine speed is between 400-3,000 RPM.
  
• The barometric pressure (BARO) is more than 74 kPa (10.7 psi).
  
• The mass airflow (MAF) is between 5-90 g/s.
  
• The fuel level is more than 10 percent.
  
• The throttle position (TP) is less than 90 percent.

Conditions for Setting the DTC
The average long term fuel trim value is below -13 percent.
All of the above conditions are present for 40 seconds.

Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Diagnostic Aids
Fuel contamination, such as water or alcohol will effect the fuel trim.
A malfunctioning MAF sensor can cause a rich condition and set this DTC. Refer to DTC P0101 .
Use a scan tool in order to review the Failure Records. If an intermittent condition is suspected , refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.

If the conditions were not corrected, refer to Fuel System Diagnosis for a possible fuel problem.

An EVAP canister that is saturated will cause a rich condition. Fuel in the vacuum line to the fuel pressure regulator indicates a leaking regulator. If the conditions were not corrected, a worn cam, worn intake or exhaust valves, or other engine mechanical failure may be the problem.

 

Great! Thanks for the details!

 

I am gettin these same codes (P0172 and P0175) intermittently as well. Check engine liht will come on for a few minutes and then go out. t has done this twice now in the last 2 days. In both cases, by the time I shut the car off, go inside to get my instructions and code sheet to check it, it shows as an H. So the problem is short lived.

If I read the information posted here correctly, I should assume that I have either a MAF sensor going bad, or a saturated EVAP canister?

The car is a 2002 C5Z, headers, high flow cats, and a tune. This was all done by the previous owner and has ran fine since I bought it 2 years ago. Thanks.

 

I've read somewhere that overfilling the fuel tank beyond the first "click off" may cause the fuel to backup and saturate the EVAP canister.

 

I always stop when it shuts off the first time...I see no point in squeezing a few extra ounces in there. But I have heard the same...thanks for your input.

 

This happens to me when I'm getting close to needing an oil change. when was the last oil change done?

 

Last week

 

probably been a few months. The car hasn't been driven much. It's only got 8000 miles on it for a 2002.

 

What would an oil change have to do with running rich? can't imagine the possible connection.