OBD-II Codes
 

Hey guys,

I'm throwing a few codes and I needed some help tracking down what the probelms is. The codes are for a 97 T/A WS6 Mods are - K&N Filter, Ported MAF Ends, Hooker Catback and Cutout. Im Throwing codes P0172 & P0175 (System Too Rich, Bank 1 & Bank 2) P0420 Catalyst System Efficiency Below Threshold (Bank 1) and P0441 Evaporative Emission Control System Incorrect Purge Flow. Note! I was throwing these codes before the MAF was ported and the cutout was installed. I'm figuring these codes have to do with my Cats being clogged? Or My Post Cat 02's needing replacement. Or maybe both? Im not sure if one would cause the other? I've been getting the EVAP code for over a year now. Also would throwing these codes cause my computer to pull timing? And if the 02's were bad and cats clogged would I be loosing a great deal of performance?
Thanks for any instruction and help.

Kevin,

I'd say it has something to do with the O2 sensors... Do a search on some of the same stuff.. you'll find your answer...

Thanks, I searched around and found some different responses. Some say its the post cat 02's some say it's the pre cat o2's? them some say it's the cats? Any suggestions where I should start??

The P0172 and 0175 trouble codes indicate a problem with the long term fuel trims being too rich, in spite of the PCM's efforts to remove fuel in response to a preceived "rich" condition. If you get a scan done, you will find your LT corrections have bottomed out at 108 in a few cells, and its still not able to pull the A/F ratio down where it belongs.

This can be caused by anything that causes the engine to actually run rich:

-excessive fuel pressure
-saturated EEC canister
-broken fuel pressure regulator diaphragm
-faulty MAF sensor
-faulty MAP sensor
-faulty TPS sensor
-EGR stuck open

It can also be caused by things that incorrectly tell the PCM the engine is running rich:

-faulty O2 sensors
-leaks in the exhaust before the O2 snesors
-excessive misfires

You need to work your way though that list. The fact that you are getting P0441 for the EEC system might indicate a problem there.

It is not likely that faulty cats would cause this problem, but it is likely that running excessively rich could damage the cats and cause the P0420.

Fred,

Thanks for the input! Does make sense about the EVAP system purging fuel fumes when it's not supposed to causing the PCM to not be able to recalcualte. So to start testing, here's what I will do. Please correct me if i'm wrong.

-excessive fuel pressure
(Check with gauge, shoud be around 42psi?)
-saturated EEC canister
(Visually inspect canister, check for implosion and leaks?)
-broken fuel pressure regulator diaphragm
(Should be ok if fuel pressure is correct?)
-faulty MAF sensor
(Check Voltage with voltmeter?)
-faulty MAP sensor
(Check Voltage with voltmeter?)
-faulty TPS sensor
(Check voltage with voltmeter?)
-EGR stuck open
(Remove and clean and inspect?, I would assume I would be throwing an EGR code? )

It can also be caused by things that incorrectly tell the PCM the engine is running rich:

-faulty O2 sensors
(Check with voltmeter?)
-leaks in the exhaust before the O2 snesors
(Visually inspect?, Smell for rotten egg smell from exhaust?)
-excessive misfires
(Would be throwing a P0300 code?)

Also, Could 1 of these 3 problems be causing this code...EEC, 02 Sensor or Bad Cat?

Thanks again!

Kevin,

-excessive fuel pressure
(Check with gauge, shoud be around 42psi?)

41-46psi, at idle, with vacuum line off. Put the vacuum line back on and pressure will drop to 35-38psi. At WOT, pressure should return to the higher "no vacuum line" reading.

-saturated EEC canister
(Visually inspect canister, check for implosion and leaks?)

Look for fuel in the vent line. That's the 3rd line in the fuel line bundle, and goes to the EEC purge solenoid on the bracket on the passenger side of the intake manifold.


-broken fuel pressure regulator diaphragm
(Should be ok if fuel pressure is correct?)

Should be, but when you pull the vacuum line off, check for wet fuel, or excessive fuel odor in the line.

============
Much easier to check the following with a scanner. Actually, you can see a lot more with a data log from some idle, "normal" driving and a WOT blast. That would also show you which long term fuel correction cells are tripping the code, which in turn tells you under what conditions you have a problem.

-faulty MAF sensor
(Check Voltage with voltmeter?)

No. Output signal is a variable frequency. You need to look at it through the PCM with a scanner. Idle should indicate 6-10gps, WOT at redline should be 220+gps. for a relatively stock engine.


-faulty MAP sensor
(Check Voltage with voltmeter?)

You can check it with a voltmeter, but a scanner will give you a reading in "Hg or kPa. You should see 9-10"Hg (30-35kPa) at idle, and at WOT, MAP value should approach BAR (also read in the PCM, and typically neer 30"Hg (100kPa) at sea level).

-faulty TPS sensor
(Check voltage with voltmeter?)

Voltmeter or scanner. Acceptable voltages at idle are in the range of 0.20-0.90V, but 0.50-0.60V seems to produce the best results for some reason. At WOT, look for a voltage approx 4V above the closed throttle reading. Voltage should increase smoothly and linearly at the throttle opens. A scanner will also show you how the PCM is interpreting this data as % throttle open.

On all of these, jiggle the harness connectors a little while reading the scanner. The MAP sensor in particular seems to have a problem with the harness connector drying out and crumbling.

==============
-EGR stuck open
(Remove and clean and inspect?, I would assume I would be throwing an EGR code? )

Might set a code, might not. Do you have any indication of a rough idle? Do you have any stumbling at low loads, continuing up to moderate loads?

-faulty O2 sensors
(Check with voltmeter?)

No. You need a scanner. For an explanation, you might want to read my online ScanMaster writeup.


-leaks in the exhaust before the O2 snesors
(Visually inspect?, Smell for rotten egg smell from exhaust?)

You will hear them, feel the exhaust pulsing out, see carbon tracks on the connections or near the manifold gasktes. If you have headers, it is very likely you have leaks. It isn't going to cause a "rotten eggs" smell.

-excessive misfires
(Would be throwing a P0300 code?)

Yes, most likely you would get the misfire code.

Also, Could 1 of these 3 problems be causing this code...EEC, 02 Sensor or Bad Cat?

You lost me.... that's what we've been talking about all along.

You probably should have addressed the code problems sooner than waiting a year, and before you made changes like the MAF sensor porting, and cutout. If you've been running "rich" for a year, its likely you have damaged the cat(s). That would explain the "low efficiency code". I've explained how the EEC problem COULD have caused the "system rich" problem, which COULD have caused the "low efficiency" problem. But thats just one POSSIBLE scenario. You need to get a good data log with a scanner like AutoTap, and let someone who knows what they are looking for take a look at it.

Thanks again Fred, you've been a great help.

What I meant with the last paragraph was, If 1 of those scenarios, (EEC, Cat, 02) was damaged, or not working properly, would that have caused the long string of codes, such as EEC causing the EEC and 02 codes then because of those damaging my Cats..ETC...But you have answered that question already.

Again thanks!

Kevin,