I just got longtubes installed and the o2 sims I ordered were the wrong ones(flat connectors). The performance I was expecting is not even close to being there. Will the o2 sims make a difference because I searched on the topic and some people say they dont maka a diference at all? So I'm running no rear o2s. Need opinions, really upset. thanks

 

From experiance I can tell you that the O2 Sims, Plug in CAGS removal and other plug in type Simulators can be a pain. Being hesitant of programing my PCM I had bought a pair myself and of course they did not work. Not that there is anything wrong with using them, but there are maybe better options.

You may want to look into getting a tune from MadZ28.com I have dealt with them personally to remove my skip shift light, SES light (O2s no Cats), adjust fan temps., and add a performance tune. Car is stronger and runs great. To swap out the pcm with a tuned unit from madz28 took <15 min and no jackstands needed for install!

 

The rear 02's only tell the pcm that the cats are working.
They don't do anything that the pcm used to make adjustments.

 

Unplugging rear O2's will result in setting SES light only. Emissions stuff.

 

I was worried that it would cause the car to run to rich.

 

remember guys that have emissions cannot just get the codes tuned out. you will need the sims to pass.

 

Here is all you need.
http://www.o2sim.com/6928.html
I use them in my pickup after having gutted the cat.

 

Good point. I hope emissions testing never comes to Alabama.

 

I am confused about this whole 02 sim thing. I am throwing codes for my driver TOP bank 02 sensor and my passenger BOTTOM 02 sensor ( I am guessing top means from the manifold and bottom is by the cat ). If I didnt want to spend the $125 quoted from GM for the cat 02 sensor is that where I replace the sensor with the simulator? Is it just a plug in deal or what, those pics on the link make those things look alot different than I was planning. Do they go in the o2 sensor hole, or what do I use to plug up the old hole if I dont use it anymore? You just run manifold o2's and then simulators on the cats right? Do I use one or TWO simulators for my rear sensors, uhhh thanks for the help

 

You leave the O2 sensor in the pipe and in the case of the sim I listed above, you splice the output wire of the simulator into the signal wire from the O2. The simulator sends the signal to the PCM instead of the O2 thus making the PCM think the O2 is working. You also have to connect 12 volts and ground to the simulator. The simulator I got was the 2 channel unit. It provides 2 seperate outputs so you only have to buy 1 simulator for the 2 O2 signal wires. Some much more expensive simulators are just plug in type which will simply do just that, plug into the connector for the O2 sensor. In either type, you leave the O2 in the pipe.

Since you still have an issue with the pre cat sensor, you have other things to check first. The simulators are only used for the after cat sensors. The ones before the cat are used to control fuel mixture. Since you have a code (it would be nice to know which code ) you have to deal with that first. Also keep in mind that if you have a cat and are getting a code for cat efficiency, your cat(s) are probably bad.

One last thing to know. The sensors that our cars use are common for that era. They must receive air (O2) in order for the sensor to work. Ours rely on the wires, or should I say the holes the wires pass through, to allow O2 to enter the sensor. If you splice and solder the wires to an O2 you chance blocking this source of air to the sensor and causing it to malfunction.

 

Thanks Don!!! That cleared up ALOT of my questions. I will have to replace the upper 02 sensor for sure, but how do I know if I just have a bad lower o2 sensor or a bad cat? I hear alot of muffling grumbly sounds from near my cat and I thought originally that it was an exhaust leak but now I am not too sure!!! Are the $60 high flow replacement cats from Summit good enough??? Here are the codes I got the last time I checked:
1. p0102 MAF circuit low imput
2. p0141 02 sensor Heater Circuit Bank 1 Sensor 2
3. p0400 Exhaust Gas Recirculation Flow (egr I guess)
4. p1153 Manufacturer-specific codes......

I just got a new stock MAF, and egr blockoffs, but I was told the 1153 is an o2 sensor code.....what do you get from it? THANKS===

 

You should check the wiring carefully to the O2 in question. You can also confirm the heater circuit with an ohm meter.

I believe the block off plate will not cure your EGR problem.

The 1153 is the front bank 2 sensor switching problem. There are a couple of things that can be done with a scanner, but you can test the problem easier by swapping the 2 front O2's. Your o2's don't indicate you have a bad cat. But you can check for a broken core by tapping on them with a rubber mallet. It's a little more envolved to do a back pressure test but that is the best way to see restricted exhaust component.

Dave

 

Dave your awesome. I appreciate your help. Today my SES light turned itself OFF again....why would it do that with ALL 4 of those codes not even being related to each other? Does it sound like I have a pcm problem?! What is the heater circuit.....does that mean the actual "heater" like you use in the winter? You think I should buy two new front o2 sensors, and then use sims on the other two/one that I have? I know I only have one cat so I should only have one o2 sensor down there, right? Thanks-

ps I am going to get the egr tuned out and then block it off---alot cheaper than fixing it and I dont really see the need for it, unless you can show me otherwise

 

P0102 is for a low frequency output on the MAF. That means the flow the MAF sensor is showing is much lower than the PCM calculates it should be (it can look at MAP, IAT and RPM and calculate the mass air flow to check the MAF sensor). Try replacing it with a sensor that is known to work. Might indicate the sensor is dirty, might indicate its faulty. A scan log would show what the MAF sensor is reading, and that might give clues to the cause.

P0141 is for the heater power circuit to the driver's side AFTER-cat O2 sensor. You have "4-wire heated" O2 sensors. There is a small heater circuit in the O2 snesor to keep it hot enough to operate. It gets +12V and a ground from the wiring harness. Either the heater circuit in the sensor is burned out, or the wiring is bad. Swap the two AFTER-cat O2 sensors side to side. If the problem switches to the passenger side, its a sensor problem. If the problem stays on the drivers side, its a wiring problem. You could also check for +12V across the power supply and ground wires in the harness.

P0400 sets when the PCM closes the EGR valve and doesn't see the expected change in MAP pressure reading. Blocking off the EGR system will just make it worse.... that's how it can tell you've blocked off the system.

P1153 is slow switching on the passenger side BEFORE-cat (manifold) sensor. Usually indicates the sensor has been contaminated, although a problem with the heater circuit might also slow it down. Or maybe its just worn out. Again, it you could swap the BEFORE-cat sensors from side to side, it will tell you whether its the sensor or the wiring. Most likely this one is for the sensor itself.

 

Many unrelated codes can be due to a bad alternator. Usually the codes are totally random if that's the case however. To elaborate, what sometimes occurs is the diodes in the alternator go bad and allow AC out on the normally DC output. The hows and the whys aren't near as understandable as the easy test to find it. Simply measure the voltage from the output stud on the back of the alternator to the negative terminal of the battery. BUT you use the AC setting on the volt meter. The reading should be .03 VAC or lower.

Also the heater circuit we spoke of earlier is in the O2. There are 2 sections to a 4 wire O2. 2 wires are used for the sensor circuit that detects the presence of O2 and the other 2 wires are used for heating up the O2. Your indication was the heater circuit had a problem.

No I don't think you should buy 2 O2s. Swap them from side to side and see what happens.

Dave