all 4 o2 sesors reading bad

[transam01]

I have a 2001 WS6 TRANSAM. Just had code read. P0131, P0151, P0137, P0157. Both converters were changed at around 12000 miles. The car has been running a little funny for awhile. A couple of months ago it seemed to have a pre-detonation sound at full throtle starting at about 4500 rpm. It seemed to go away. then it started to run a little funky at part throtle. so i gave it a hard full throtle run. halfway through the run the ses light came on. thanks for any ideas.

M.J. COLE

[Kevin - Blown 95 TA]

If you want to see what the sensors are doing, you need a data logger or scanner that can record how fast the sensors are switching (if at all). It's hard to do with a meter, especially a digital one. Otherwise, a dealer (not recommended) or a repair shop can hook up a Tech2 and look at the switching for you and see if they're bad. If something poisoned the converter, maybe it took out the sensors too. What was the reason the converters were replaced? Any chance you got a tank of bad gas?

[N20LT4Bird]

The chances of all 4 O2's going bad at once are slim to , unless you ran leaded gas through or had two blown headgaskets or something. I didnt look those codes up, but I would assume that they are indicating a rich or lean condition (probably rich if your cats are going, but then again, if your detonating, maybe lean ). The O2's not switching are probably due to a TRUE rich or lean condition. Check your fuel pressure, injectors, and fuel pressure regulator. You probably have issues with one of these. If not, you may have a bad MAF or ECT, fooling the PCM into producing improper A/F ratios.

If you posted what the codes indicate, I can help you better.....

[Injuneer]

The code is for "low voltage" on all 4 sensors. Sounds suspicious.... a tank of leaded fuel, as suggested above - actually it would take many tanks of leaded fuel to do that much damage. But extended use of leaded fuel might account for the fact that the cats were previously replaced. Why did they need replacement at 12K miles?

[N20LT4Bird]

"Low voltage" would indicate a lean condition. I would check your fuel pressure first.

[transam01]

Thanks for responding

I don't know why the converters were changed. I had the ses light come on, I took it in, they said one was bad. A couple of months later, same thing other side. I wonder if the error codes might be on my dealership service reciepts. I have only run premium gas. I live in mid-michigan. I did notice a drop in gas mileage after the converter repairs. I let the dealership know about that when I was in for other repairs. The change in mileage was from around 19-20 to 14-15 miles a gallon. My gas mileage seems to be unaffected or getting slightly better now. The gas mileage is around 18 miles a gallon now . The car now has 30,000 miles. At times, the the motor seems to surge and or dip engine power on acceleration. This engine also consumes oil, as described by other transam owners. The consumtion is not too bad, but is there the less. When my car was experiencing the seemingly pre-detonation problem (early thru mid-summer), I did use octane boost in one tank of gas, I was thinking that mabey the gas was'nt up to standards around here. It had no effect on the marbley crackely sound at full throtle (4250-6000rpm). The pre-detonation effect has been gone a mabey a couple of months now

I want to thank the people that responeded, I apperciate the help.

M.J. COLE

[Squat13]

did any of you guys ever think there is a wiring issue. Maybe a bad ground. The first time I changed the starter on my TA, foe some reson I out a small ground wire on my bindix that should have been bolted to a oil pan bolt. The car would throw codes like a monkey with a HAND FULL. Check your wiring, maybe something fried.

[Injuneer]

The decline on gas mileage and some of the other symptoms are pointing in the direction of a "false lean" condition.... the O2 sensors indicate lean when it really isn't lean, and the PCM adds fuel it doesn't need and you end up running rich. Running excessively rich for an extended period of time can kill the cats. Do you smell fuel in the exhaust at any time?

But that conflicts with the noise you are hearing.

"pre-detonation".... do you mean a rattle, like ball bearings in a can, indicating pre-ignition (ping) and/or detonation (knock)? If you can hear ping or knock, you have a problem. The knock sensors are supposed to pick up the noise at a level too low for you to hear, and retard the timing to prevent the knock and the resulting engine damage.

Have you ever had the car on a scanner? Have you (or the dealer) checked for knock retard when you hear the "pre-detonation"? If you know someone with AutoTap data logging software, it would be a good idea to have them log the PCM under a wide variety of operating conditions, from low load cruise, through a WOT pass to max RPM. With that data, it might be possible to detect the cause(s) of the problem. Has the dealer even commented on the noise, or offered to do a data scan using his Tech II?

Since you feel you are hearing some form of detonation, do NOT abuse the car with excessive WOT/high RPM operation, or you can damage something.

EDIT: One thought that came to mind as I hit the "post" button..... Is it possible the noises you are hearing at WOT are in fact exhaust leaks? Exhaust leaks can sound like ping, and exhaust leaks before the O2 sensors can cause a "false lean" condition.

[transam01]

The sound almost seemed as if it were coming form under the car. At times I thought it could have been unburned fuel in the converter. I have little to no experience with these newer type of engine controls. please take that into account if I say something too ridiculous.