What is the low voltage? The voltage going to the o2 sensor heating elements or the voltage being generated by the o2 sensors?
I also have the eBay CD's but they only include the 2.7 info. I think eric355 sent me the 5.2 schematic that I have. I also have a troubleshooting guide somewhere. I don't have any other schematics though, sorry.
The generated voltage. However, one of my sensors had a short or something in it so when I plugged it in, it brought the levels of all the sensors to zero. Here is a picture from my debug efforts. A: all four sensors disconnected with car running idle. B: connect passenger side pre-cat sensor bank2 sensor1 C: disconnect bank2 sensor1 D: connect bank1 sensor1 E: disconnect bank1 sensor1, connect bank2 sensor2, apply some RPMs F: leave bank2 sensor2 connected and connect bank1 sensor2 G: Apply RPMs H: Connect bank1 sensor1 I: Apply RPMs J: Disconnect bank1 sensor1 K: Connect bank2 sensor1 L: Connect bank1 sensor1 M: Disconnect bank1 sensor1 Image Unavailable, Please Login
Some nice troubleshooting there I hope to eventually install a couple of Wideband o2 sensors with guages to keep an eye on things and help evaluate future problems.
Try cleaning and tightning grounds above both the left and right hand radiators...i have also seen where people trying to remove the engines for the service have forgotten to disconnect the harness and broken several wires.
Consider something other than factory headers. I have Fabspeeds at 1/2 the cost and they're excellent. Try fabspeed.com . Geno
I am still fussing with this issue. I tried disconnecting the Pre-Cat O2 sensors and ran the car. The car ran rougher than usual. Then I disconnected all four and again the same. Then I switched the pre and post O2's to see if the wires were somehow switched and the car ran very rough and almost stalled. That tells me that the O2 Sensors are communicating with the ECU? I then tried to hook up an extra CAT-ECU that I have to see if the ECU's are bad and still got all four codes. A new twist on this: I checked my Exhaust by pass valve with the engine cold started and it was closed. There is no vaccum on the line that engages the valve. I did vaccum test on the line and with hand vaccum the valve operated. I did not get any suction on that line, cold or hot engine. I vaccum tested all the segments and they check out. My air pump works fine when the engine is cold and makes the infamous whistling noise. I checked the vaccum line from the engine to the canister in the rear corner of the car and it did have engine vaccum to it. Does anyone know the operation of that mechanism? Do the switches at the bottom switch off or on the suction? and at what stage. And the $64,000 question: can this cause all four O2 sensor low voltage issue? Perhaps make the engine run too rich and throw off the sensors? Loser, thanks for the offer, I may have to take you up on it, but it would have to be before end of May since my registration expires at that time and I will have to register the car as Non-operational since I cannot get it smogged and after that I cannot drive it. What a waste since the car runs like a champ.
Hi Andmoz, If you are not getting vacuum at the valve, then I would expect a P1448 code. See other related threads. Do you have a complete list of codes from your car? I am assuming your four codes are all O2 related. My car is in the shop getting the leather worked on and I expect to have it back tomorrow. If you want to get together sometime, the sooner the better. I may need to sell my car soon Tom
Hello Tom, Actually I do get P1448 in between my four other codes. I will email you tomorrow so we can arrange a day. thank you
Just a quick update. We used the same diagnostics method mentioned above to narrow the O2 issue down to the bank 2 pre-cat sensor. We replaced the sensor and the O2 issues are gone. The P1448 appears to have been the result of a dirty connector. We cleaned the connectors to the vacuum control valves and the issue is gone for now.
Thanks to Loser, my problem is solved. His knowledge and kindness took care of the problem. I was able to get my California smog certificate. I have driven the car over 400 miles and no O2 sensor issue yet. Thanks Tom.
