QuestionI have a 1996 Sedan De Ville Northstar which I have owned since new. It now has 167,000 miles on the clock. The engine suddenly began running sluggishly, with low power at lower speeds (and perhaps higher speeds as well) and an occasional "buck" or "backfire". I have run the diagnostic codes, which indicate that all 4 O2 sensors are bad, among other things. The related codes are 154, 155, 141, 140, 135, and 147. I am assuming that 155, 141, 135, and 147 ("Heater performance" in Bank 2 Sensor 1, Bank 1 Sensor 2, Bank 1 Sensor 1, and Bank 1 Sensor 3, respectively) indicate "bad" O2 sensors, but I don't understand 154 and 140 ("Circuit insufficient activity" in Bank 2, Sensor 1 and Bank 1 Sensor 2, respectively). I have purchased 4 new O2 sensors (2 # 13444 and 2 # 13474). I believe that the 2 # 13474 go in each manifold, and that the 2 # 13444 go in front of and behind the catalytic converter. Before I proceed with R & R of the 4 sensors, have I got the whole thing correct regarding where they go? Also, I am assuming that R & R of the ones on each side of the catalytic converter will be relatively straightforward and not too hard, although I haven't looked at the situation and locations. Is this correct? Regarding the sensors on each manifold, where are they exactly? What is the best "attack" method of getting to them? From above or from below? Which other parts need to be removed to gain access? Is the "special" socket wrench necessary, or can a regular open or closed end wrench do the trick?
Diagnostic Code 300 also came up (Engine misfire detected") and I am assuming that this is related to the O2 sensor problem. True or false (or maybe)?
Diagnostic Code 741 also came up ("TCC system stuck off"). What in the world does that mean? I had the tranny rebuilt a a year or so ago (non-GM rebuilder) (second time, the first time was a year-and-a-half prior to that), and the
"Transmisson Problem" warning light came on after each rebuild. The rebuilder found nothing wrong each time, and had even used the upgraded solenoids or whatever, so I took it to my Cadillac dealer each time and they too found nothing wrong other than the codes indicating torque converter problems (new torque converters were used in each rebuild). The tranny seems to operate fine, other than an occasional "Gear Select Problem" warning that goes away once the tranny is shifted in to drive or reverse. Any insight?
Finally, Diagnostic Code 1599 came up ("Engine stall or near stall detected"). Any insight into this code?
By the way, the engine computer was replaced at my dealer a year or so ago as well.
Thanking you profusely in advance...
Robert Dobson
AnswerI have NEVER seen all 4 o2 sensors go bad at the same time EVER.
I think your lack of power and your codes are more likely being caused by restricted catalytic converters which is quite common on high mileage vehicles.
I would perform a back pressure test on each exhaust system BEFORE I replaced any parts. If your not getting enough air flow thru the exhaust this will cause your lack of power and the display of all your codes EXCEPT for the 741 TCC one.
The TCC (Torque Converter Clutch) solenoid is what engages and disengages the overdrive circuit within the transmission and these solenoids are famous for failing after 30 to 50 thousand miles and I have seen many fail within 10,000 miles. The TCC solenoid on the front wheel vehicles in under the SIDE PAN of the transmission behind the drivers front wheel. You have to remove and or manipulate the pan JUST right to get it out of the way in order to replace the solenoid. On the REAR WHEEL drive vehicles the solenoid is under the BOTTOM PAN of the transmission.
Look in your book and perform the procedure for the EXHAUST BACK PRESSURE TEST for both exhaust systems. If I had the vehicle in my shop, This would be my FIRST test before I replaced ANYTHING.
I don't understand WHY you would have to rebuild the trans TWICE in the lifetime of the vehicle. I can't remember EVER rebuilding a transmission a second time once I rebuilt it the first time around. Either the rebuilder is not doing a complete rebuild and is only replacing the parts that have obviously failed and NOT replacing the worn parts that should be replaced when you do a complete rebuild. I have been rebuilding transmissions for well over 25 yaers now and this second rebuild should NOT have been needed if the job was done right the first time.
I don't know who's doing your work for you but I would be extremly careful.
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