on my 96 WS-6, i have had a SES light turn on and sometimes before i can get the scan tool from my brother (a week sometimes) it will go off. then back on. So i finially scanned it and the codes were P0171: fuel trim bank 1, P0174: fuel trim bank 2, and P0430 TWC system low bank 2. I have the actual service manual the dealership uses and it says for both the P0171 and P0174 to first correct any other codes. I trouble shot the P0430 and it states the cat could be leaking, damaged, or bad.

Before i buy a new cat, and 4 O2 sensors, has anyone ran into this problem? I've searched the forum under o2 cat, but not much was resolved (a pet peve of mine) just questions, suggestions and nothing.

How could the SES light turn on, then off later? Does anyone think its another sensor setting these off?

the car has 118k miles and the cat looks original, but i don't konw about the O2 senors. previously i was daily driving the car as it sets for 6 months with no problems.

thanks and I promise to leave a detailed post on the resolution of the problem...when i get there.

And recomendations on Cat and O2 sensors would be appreciated info on car is in my sig.

 

The SES light only stays on when the code is "Active". If the problem goes away, the light goes off, but the code stays stored in memory. P0430 sets when the PCM compares the after-cat O2 signal to the pre-cat O2 signal. The after-cat signal should cover a narrower range than the pre-cat, because the catalytic converter is supposed to be storing excess O2 from the NOx reduction, to use for HC and CO oxidation. If the problem is borderline, its possible that the diagnostic test could pass some times and fail others.

To check the after-cat sensors, swap the two sensors side to side. If the problem stays on Bank 2, its a converter problem, or the lean condition evidenced by P0171 and P0174 is upsetting the relative signal levels of the pre-cat and after-cat sensors. If the "problem" follows the sensor, its a sensor problem.

This is one case where I would trouble-shoot the "lean" codes BEFORE trying to fix the P0430 problem. P0430 will not cause the "lean" codes, but the lean codes may be interfering with the P0430 diagnostic routine.

The "lean" codes are not necessarily sensor problems. Appears something is forcing the PCM to add a lot more (20+%) fuel than it is normally supposed to supply, in response to a measured lean condition. Since its happening on both sides of the engine, you have to look at things that can affect both banks. Low fuel pressure, a tear in the inlet elbow after the MAF sensor, a dirty MAF sensor, a massive vacuum leak - are all suspects at this time.

 

i read the ShBox write up on the fuel presure check and i hooked up a fuel presure guage to the line and with the ingniton on i have 41psi, when the motor is running it goes to 48psi. I took the vaccum line off and it stayed at 48 and it doesn't seem to be getting any vaccum to the reulator. i don't know if this is the problem or a different one. The vac line is good and new, but the box near the intake that the line connects to isn't providing vaccum. I'll have to check it and see what the deal is.

Does it sound like I'm going in the right directing?

 

The fuel pressure regulator vacuum compensation line doesn't connect to a "box"..... it connects directly to the nipple on the side of the intake.

Courtesy of Shoebox - it should look exactly like this:

http://shbox.com/1/fp_reg.jpg

 

thanks, i had the line to the EVAP switched, and there were several lines on that side of the intake that were old/rotten. I replaced them and rerouted them, ran the fuel presure check and its at 39psi with ignition on (motor not running) and 40psi with motor running. I disconected the vacuum line and it went to 47psi. This is slightly lower than it says on ShBox, to be 41-47psi. Tomorrow i will try to reproduce the codes in my first post.

Does the 39-40psi seem too low? could this cause my codes?

 

40psi with the vacuum line corrected is fine. You want 41-47psi with the vacuum line disconnected.

The injectors do not need 43.5psi at the rail. They require a 43.5psi DIFFERENTIAL pressure. That is what determines the flow through the injector - the DIFFERENCE between the rail pressure and the manifold pressure. As manifold vacuum increases, the rail pressure had to drop to make the DIFFERENTIAL pressure 43.5psi.

47psi with no vacuum compensation is on the high side of the allowable. That simple means your injectors will flow about 4% more than they are rated for. That is within the PCM's ability to correct the fuel flow rate by using the long term fuel corrections to shorten the calculated pulse width.

 

awesome, i will try to duplicate the conditions that caused the codes to pop up, and i'll post some results.

 

ok so i test drove it and it gave the same P0430 code and a P1441 code. I found another bad vacuum line under the drivers seat (outside the car near the fuel lines) so that should be done. Then i started to pull out the dowstream O2 sensors and switch them (as Injuneer recommended). Well i couldn't get the hard one to get to off so i dropped the pipe and had to heat it up to get it off. Its off now and the treads were messed up. I don't want to put the opposite side O2 in the bad hold and mess its treads up, or put a possible new O2 in the bad hole either. I figure i can weld in ( i have no problem welding it myself) a new bung or find a re treading kit to try and clean the treads up.

I'm guessing welding a new bung would be easiest? I could put it in a better spot, easier acess. Suggestions? Looks like i will need at least one O2 sensor maybe more, and suggestions on were and what brand to buy?

 

Get the correct size "THREAD chaser".

M18 x 1.5

 

i found a thread chaser at Harbor freight for $1.56. Any help on the o2 sensor? best place to get one? I read on several threads here the bosch O2 sensors don't last long. Most auto parts stores around here just sell Bosch and denso. Do these last?

 

Get an AC Delco (now "Delphi") sensor. Shoebox has the part #'s on his site:

http://shbox.com/1/Parts.htm

 

you can get an ac delco O2 from rockauto.com for like 65 bucks iirc

 

I got the thread chaser and cleaned them up and switched the O2 sensors. I replaced several old cracked vacuum lines in the engine bay, on the EVAP switch, PCV and CCP system. I sent my extra PCM off to get tuned, and the tuner suggested I replace the MAF with one that isn't descreened and ported. I had an extra stock one and took the ported one (it came with the car) off. Put it all together and it runs smoother, and after 2 days of driving, i finially got a SES Light. Now its throwing codes P0161 and P1441.

Its strange when the P0171 and P0174 went away, and now the P0161 showed up. I'm not too concered bucause i had the tuner tune out the rear o2 sensors, so that problem should go away. The P1441 is anoying. I've replaced the vacuum lines to everything on that side, I guess checking the switch and tank is the next step?

I noticed when i filled the gas tank this morning, i could put the nozzel in and squeeze the handle fully without it splashing back during the first half of the tank fill up (if i explained that coherently).

any guidance on a P1441 code?

 

P1441 indicates the PCM has detected a vacuum in the EVAP system, on the wrong side of the EVAP purge solenoid, when the solenoid is supposed to be closed. Could indicate the purge solenoid is stuck open, or it could indicate a problem with the vacuum detection switch - part #11 in the diagram linked below. Another possible cause is having the two vacuum lines to the EVAP purge solenoid switched. Check the lines per the photo linked below.

Courtesy of Shoebox:

http://shbox.com/1/1996_evap.jpg

http://shbox.com/1/evap_sol.jpg