not sure how many of you have read my threads about the ses light, and my neverending issues with my car! anyway the usual symptoms, car stalling, wont start, very erratic idle, etc,etc,etc.so it take it to gm. they tell 75 for scan! ok so i ask if u do that and fix the problem do i still have to pay for the scan? they say no. so they scan it. 2 codes. MAF and MAP. so they say i need to replace one of them. i tell them that i already have and took them out becuz they didnt fix the problem. so they check the voltage at the MAP sensor and it is fine. but on the scan it showed -0.02 volts. so they said that my comp is bad. damnit. anyway it is under warranty, so all will be FREE. if that is the problem.
but my bank 1 sensor 2 is only showing 17-21( not sure if that is volts or what it is.) but the other 3 o2's are giving normal numbers like 150-800. so i tell them that could be the problem or that o2 might be bad, and he said if it was bad that it would throw a code. hmm can someone better xplain that one to me. if the other 3 are doing what they are supposed to be doing then that 1 is possibly bad if u ask me! anyway i have the madz28 tune and the lt4 km, so when they put the new comp in i am going to lose both of them! what do u guys think of this situation ? do u think the comp is really bad? i just want to make sure that i am doing the righ thting b4 i give up 150$'s for the lost parts!
thanks in advance
p.s. sorry for the long post

 

You can take out the LT4 KM out of your old PCM before you give it back to them. I will be more than happy to put your tune on the new PCM for you just for the cost of shipping, but I really doubt there is anything wrong with the PCM. I bet you have a wiring problem like I said the other day.

 

hey i sent u an email madwolf. thanks for helping me out here. i did try asking them if there was a wire form the map to the computer that could be loose, and he said" that is one straight shot from the map to the comp, and i really doubt that, that is the problem.) here is a quote from one of the emails i get from autotap.com
The O2 sensor is mounted in the exhaust manifold to monitor how much unburned oxygen is in the exhaust. The signal from the O2 sensor tells the computer if the fuel mixture is burning rich (less oxygen) or lean (more oxygen).

A lot of factors affect the richness or leanness of the fuel mixture, including air temperature, engine coolant temperature, barometric pressure, throttle position, air flow and engine load. Other sensors monitor these factors too, but the O2 sensor is the master monitor for what’s happening with the fuel mixture. Problems with the O2 sensor can throw the whole system out of whack.
from what that says i still think it could be that one front 02 that is throwing the map voltage off! anyone else think so?

 

Can't see how the wrong A/F ratio would throw off the MAP readings or the sensor. A vacuum leak, improperly adjusted intake valves, burned valves, etc will affect MAP.

Since you had a code for the MAP, which one was it.... high MAP or low MAP? Did they check to see if they are getting the correct +5V reference signal to the MAP sensor connector? Did you inspect the MAP sensor connector? It is not unusual for them to get brittle and crumble, causing voltage problems.

On the MAF, did you check to see if you are getting a +12V power supply on the pink wire to the harness connector? That wire seems to be a frequent problem on the 97's for some reason. Again, what was the specific code? There are a couple of MAF related trouble codes.

 

when they did the map voltage check. it came back with like 15 volts ground. then they checked the refernce signal that was 5. then checked power. said it was all fine. so from that the guy said that the map at that point is gettin the right voltage so it has to be in the comp. and the codes i was getting i dont really remmeber what they were offhand. but one of them was mapo votage/lowinput. p0107/ p0101/ p0103 i believe. at one point i was gettin 6 different codes for the maf and map sensors! and the connection is good.
so now to the other part. do u think my 02 is bad. it is the one behind the first cat? the other 3 02's readings are all over the place, then this one sits right at 17-21! any ideas!
well tomorrow mornin they are gonna put the new comp in, and i will go from there. if that dont fix it , i think it is the bank 2 02. thanks again guys.

 

well took it back up there. they changed the computer, didnt do anything. so they look around for an hour, and they say it is connector B, wire from the MAP to the computer has a bad connection somewhere, so i ask what color it is and says he is pretty sure it is the green one. so my ? now is does anyone have any pictures of this wire and how to folow it, cuz i really cant see where it goes? thanks in advance

sincerely,
want to get this fixed

 

Some of what they are telling you makes any sense at all, or you missed a decimal point. How could the MAP sensor show "like 15 volts ground." Makes no sense at all. Where would you find 15V in our cars? Did they read the signal on the green wire at idle? Should have read about 1.5V at idle.

Pin B on the MAP sensor is the green wire (MAP "signal"), and it connects to pin C23 on the PCM. You have to check the continuity from both ends. P0107 = MAP sensor low volts. The other two are MAF sensor codes. Have they figured out the problem with the MAF sensor yet?

You should stop worrying about the after-cat O2 sensor until you get the other problems fixed. That sensor is not causing MAP problems. Your quote simply indicates that barometric pressure affects A/F ratio - and it does, because barometric pressure affects the density of the air, which affects the pounds of air combining with the pounds of fuel. But that doesn't mean that feedback from the O2 sensor can affect MAP readings. Not related at all. The after-cat sensor affects nothing. Its just there to tell the PCM whether the cat is working. If you feel its a problem, swap the after-cat sensors side-to-side, to see if the problem follows the sensor (bad sensor) or stays where it was (bad cat, or bad wiring). Is the PCM setting a code for a faulty O2 sensor? The after-cat sensor should NOT move around at the same extreme range as the pre-cat sensors. They will typically operate over a much narrower range, maybe less than 1/2 the range (300-600mV) compared to 100-900mV for the pre-cat sensors. The PCM is not looking for any more activity than that.

 

thanks injuneer, u answered my ? for the 02's. now to the MAP, it showed up -0.02 volts. and i probably made a mistake on the 15 volt, might have been trying to say it had good ground. i am not sure if they checked voltage at both ends! they wanted me to pay hourly after that and i figured since i now know the problem i would try to fix it, rather then pay them 75 hour!
So would it be easier to run a new wire from MAP to computer? or follow this one and find the short? and is the pics anywhere that i can see where pin c23 is at?
thanks again , and cant wait to get this fixed!

 

does "10 kpba" or something like that sound familiar? cuz when i walked up they were pointing at that, then they told me i couldnt be in the bay area! then they walked over to the computer for 20 minutes staring at that, i am thinking they were looking at what that meant, dunno.
map sensor 10 kpba
if that helps, thanks again. and tonite i am going to try and fix this. then once this is done, i am hoping that is has something to do with the MAF and if not then i will start chasing that wire as well.

 

hopefully i just fixed it! went ot autozone and bought me a volt meter, then came home, popped the hood. started looking at the map and following the wires, then about 4 inches down( form when i did the tb bypass) it was spliced , becuz it got caught in the alternator brackets and where the tb bypass hooks back up. so i undid everything, then hooked the wires back up, and put it back together, now i have the battery unhoooked and hopefully when i hook it back up the ses light dont come back on. thansk for all ur help guys, and when u all told me to follow wires i should have atleast walked out and took a better look! thanks again

 

fixed. by fixing that piece, my rpms dont jump whenever i let of the gas, and go from 400-2000. everyone told me that was a sign of the stall. no more erratic idle! and no more ses light
thanks for the help guys!