I am in the process of finishing my car and had a couple of questions. I did a search but could not find anything.

Where does the water temp sensor plug run in the main harness?

I want to eliminate the upstream O2 do I just leave it unplugged?

Images of the harness would help.

 

Car year would help.

 

just thought about that 1995

 

The temp sensor is in the water pump. Not sure what you are asking.

Exactly which O2 sensor do you want to remove. The one after the cat doesn't really do anything in OBDI. The two precat ones are needed.

 

Well what is the sensor on the driver side cylinder head? That is what I am looking for a connection to.

Sounds good, I will hook up both precat ones.

 

Not true The 95 is a "1.5" OBD and has somethings enabled. I guess it depends on what "doesn't REALLY do anything" means

OBD-I
The regulatory intent of OBD-I was to encourage auto manufacturers to design reliable emission control systems that remain effective for the vehicle's "useful life". The hope was that by forcing annual emissions testing for California, and denying registration to vehicles that did not pass, drivers would tend to purchase vehicles that would more reliably pass the test. Along these lines, OBD-I was largely unsuccessful—the means of reporting emissions-specific diagnostic information was not standardized. Technical difficulties with obtaining standardized and reliable emissions information from all vehicles led to an inability to implement effectively the annual testing program.


OBD 1.5
OBD 1.5 refers to a partial implementation of OBD-II which General Motors used on some vehicles in 1994 and 1995 (GM did not use the term OBD 1.5 in the documentation for these vehicles - they simply have an OBD and an OBD-II section in the service manual.)

For example, the 94-95 Corvettes have one post-catalyst oxygen sensor (although they have two catalytic converters), and have a subset of the OBD-II codes implemented. For a 1994 Corvette the implemented OBD-II codes are P0116-P0118, P0131-P0135, P0151-P0155, P0158, P0160-P0161, P0171-P0175, P0420, P1114-P1115, P1133, P1153 and P1158.[1]

This hybrid system was present on the GM H-body cars in 94-95, W-body cars (Buick Regal, Chevrolet Lumina ('95 only), Chevrolet Monte Carlo ('95 only), Pontiac Grand Prix, Oldsmobile Cutlass Supreme) in 94-95, L-body (Chevrolet Beretta/Corsica) in 94-95, Y-body (Chevrolet Corvette) in 94-95, on the F-body (Chevrolet Camaro and Pontiac Firebird) in 95 and on the J-Body (Chevrolet Cavalier and Pontiac Sunfire) and N-Body (Buick Skylark, Oldsmobile Achieva, Pontiac Grand Am) in 95.


There is a primary (upstream) oxygen sensor installed in the exhaust before catalytic converter that monitors the quality of combustion in the cylinders. Based on the feedback from this oxygen sensor the ECM/PCM makes fine adjustment to the air-fuel mixture to further reduce emissions.



There is another, secondary (downstream) oxygen sensor installed after catalytic converter in the exhaust that monitors catalytic converter's efficiency.

P0420 OBD-II Trouble Code
Technical DescriptionCatalyst System Efficiency Below Threshold (Bank 1)

What does that mean?The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.

P0420 IS enabled for 95 cars according to my sources.

 

Do you have a CTS on the passenger side head?

On my 92 the CTS on the passenger side head controls the analog temp gauge. The heads are interchangeable so someone may have put a CTS in the head instead of a plug on the drivers side.

 

Bingo. Will have to change it over, could be a pain in the butt with the motor in the car, we will see.

 

Nick,
As stated above by Mk82, on the 95 the upstream passenger and driver side O2 is needed. The Rear passenger O2 can be removed with out setting off any problem codes or affecting performance. TPIS can verify this for you. I ended up having to remove the rear O2 when installing TPIS headers. It makes a good spare. Air fuel is controlled by the upstream O2s in the PCM.
Rick

 

Rick.

Thank you. I should live Friday and I will make sure that this is the case.

Nick

 

I have a 94 LT1 and the rear O2 sensor is missing as in no hole in the exhaust after the cats. The wiring is there, but not hooked to the sensor. I'm going to the muffler shop to have a hole drilled and a nut welded in and I was wondering if anyone knew what wire went to what when I get the sensor installed. The dealer said this is what is causing the "sys" light to flash. Even though when I pull codes I get C23 and C77 which are IAT sensor and primary cooling fan relay. Weird, I know. This is combined with the PKE only recognizing the remote to UNLOCK when the rear glass is up and my ongoing problem of "odo err". I am replacing the rear hatch open switch and the relay back there as the parts are relatively inexpensive and praying that the odo err will magically disappear. I did buy a used CCM off ebay just in case. By the way, CCMs on ebay are called BCMs.