here is the story.

I was driving around 50MPH flat road no bumps nothing
All of a sudden the engine starts funny and reduced engine power pops up.

I stopped and turned it off and checked then cleared all the trouble codes.
I started it back and the reduced engine power pops up right away.

I was close to home so I drove on home and let it cool off.

tried again and same result.
A few of the codes I have had over a year like c1277 and c1295

below are the new ones that just started

c1133 this one has been on before, I have had a tune to turn off the rear O2's so this one may be nothing

P0342 This one has been on for a while, the sensor was replaced and it did not help The only problem I have out of this is it sometimes takes a few extra cranks before it starts.

P0102
P1120
P1221
P1571

I have a new battery and there has never been an acid leak, the wiring and plugs under the battery look fine with no deterioration that can be saw.

i also have a c1222 which has been there for a couple weeks.
I am not in the best health and was planning checking the wiring on this when I felt better. I think it is a frayed wire.

 

The wiring and connector for the throttle position sensor would be the place to start.

 

I checked and cleaned the plugs with electric parts cleaner
I also inspected what wiring I could see

i removed the batter and looked to make sure the wiring under looked like it had acid or something and what i saw looked fine.

I am thinking that the throttle position sensor and mass air flow wires run together towards the back and disappear behind the engine that the problem may be where I can not see it

where do they go from there?

do they plug into something else that I can run a bypass wire to so I can rule out bad wiring?

I do remember a couple days ago smelling a smell like plastic burning when I got out of the car. I did open the hood to make sure a plug wire had not gotten into the header. I could see nothing and figured it may have not even been the car because the smell did go away and did not come back later when I left again, my neighbors have a fire pit in their back yard and burn leaves and stuff this time of year and sometimes their kids do toss in anything they find at times.

 

I checked and cleaned all the plugs and separated the wires from the plastic cover all the way back to the back of the engine. I found no problems like burns crimps or frayed wires.

I removed the RF wheel to replace the bad plugs on the wheel speed sensor so I went ahead and removed the access panel to look at the computers. there was some corrosion visible on the bottom of the metal one so I removed both them and checked the wiring that was visible alone with the plugs. I saw nothing wrong and the inside plugs were in perfect looking condition. I replaced the computers and battery but left the wires all separated from the harness but plugged in. As soon as I turned on the ignition without starting it the DIC said reduced engine performance popped up. I checked and the P1120 and P1221 both popped up. I tried to start it and it did start up but ran rough.

I had to stop at that point because my back pain was keeping me from thinking straight.

Is there a way to check the wires to for voltage that is suppose on them when running?

Does anyone know where they plug into the computer so I can check continuity on them?

Any help would be very much appreciated.

 

Might try pulling the TB off and giving it a good cleaning.. i have read on some Envoy forums that they will be dirty inside also I have read on other GM cars/trucks that get the P1221 that the connector for the TPS is bad inside, not visiable. GM makes a wiring harness kit to replace the connector and bad pins. might want to try that.
Uploaded on Jun 25, 2011
Pt. 2 This a very common problem with GM cars and trucks with "drive by wire" throttle. Luckily th' throttle body was good, and I was able to find th' source of th' problem.
GM harness repair kit part #88986255
Pt.1
Pt.2

 

I went out and checked the wired to the Throttle Body and none were loose, I will check better tomorrow if I can, I may try removing each wire from its base and double check for breaks.
I did remove the whole the whole throttle body to bring in and clean, there was some carbon buildup on the butterfly but some spray carb cleaner and a few paper towels and it is clean and shinny. The butterfly opened and closed easy with no binding at any position.
I removed the sensor to check inside it for moisture, it was damp inside but not soaked. I am leaving it off to fully dry. I could find no visible way to get into the sensor to check its internal condition.

The codes for the throttle position appear as soon as the ignition is turned on, if they are cleared they pop back up instantly.
The Mass air flow codes do not pop on till it is started and running, but they do come back right away if cleared while the engine is running.

My brain is telling me there must be a bad section of wiring somewhere after the harness goes behind the rear of the engine.

if I can find where these wires plug into something I can rig temporary bypass wire or do a continuity test to see if the problem is in the harness somewhere or if the problem is a failed part but I do not have a diagram and can not find one online.

 

the Throttle body is clean, no carbon at all, the flap opens and closed with normal resistance from the electric motor but no binding at all.

The sensor plug seems fine, wires are good as far as I can tell.

I removed the battery, brattery Shroud, PCM, TAC, Fuse Box, and checked all the wiring and collections I could find and get to.

I did pull the PCM/TAC wiring harness up into the battery compartment because I have a very bad back and getting up and down is very painful.

I checked all I could, including the wiring harness plugs, and wires.
I hooked it all back up with the PCM/TAC sitting in the battery compartment.

when I hooked the battery back up and turned the ignition on, not starting it. The reduced engine power came on right after step on brake to shift, I checked and the two TPS codes P1120 and P1221 the only PCM codes set both Current. I cleared them and they came right back on. Then I started it and it started right away but the mass air flow codes came on also.

I am stumped. Any suggestions?
It is my only vehicle at the moment.
What is the chances of doing more damage if I drive it to places I have to go only?

 

PROBLEM SOLVED THANKS TO RedZMonte

After trying everything I could think of and my friend with a C5 returning from a trip so I could borrow a part from his car to test

I borrowed a TPS from a friends vette and put mine on his. Mine worked fine on his but his gave me the code.
So i swapped them back and went back to tracing back wires as far as I could then used a sewing needle to probe into the insulation and checked for continuity from the pin to the plug. 2 wires showed no continuity. I them held them at both ends and pulled, sure enough they both snapped apart 5 inches from the plug. A quick test splice and plug everything back in and went sat down and inserted key, said a small prayer, talked sweet to the car and promised it a wash and wax if it worked.

Turned the switch and watched the DIC display, it went from corvette, to step on brake to shift, then instead of reduced engine performance, it said door ajar. I hit the starter it fired up and ran a bit rough for a few seconds then smoothed out and purred like a kitten.
I still have the mass air flow error that was not there a few weeks ago but I will deal with that later, I may have a vacuum line off or something.

Tomorrow I have to put everything back where it goes, do a proper repair on the wires with solder and shrink wrap.

Monday I guess it is a trip to the detail shop as promised to the car.
But the main thing is problem solved

 

Congrads! im glad it was something relativly easy to fix. a vac leak would most likely give a P0171 Lean code as long as the maf was working correctly. Might also try using some MAF cleaner on it incase it is caked with oil or dirt (over oiled Filter) but if it kicks on as soon as the engine starts i would guess a MAF problem or (Fingers Crossed its not electrical) another damgaged wire. Check the connctor to the maf to make sure its not corroded or has bent pins and is making a good clean connection. Any mods to the intake system or stock?

Good look, hope its a easy fix.
Try this before spending any time/money with anything else.
P0102 Fixed by cleaning MAF
http://forums.corvetteforum.com/c5-t...s-morning.html

 

What codes are still present and what codes are not gone?

Do you have access to a scan tool of any sort that gives a MAF reading? even the $100 cheapy ones form the parts stores i think will do real time data steam. see if you get a reading from the maf. This guy found a splice job that pulled apart (he didnt realize it was even done by the previous owner..). that will help determine if the sensor is getting a reading or if its a bad reading.
http://forums.corvetteforum.com/c5-t...rcuit-low.html


read this post for the P0120 Maf Code.. Couple guys have said they got the code from wires ribbing agains serp belt.
http://forums.corvetteforum.com/c5-t...af-issues.html

 

The Reduced engine power is gone which was my big worry

I still have the P0102 which was not there before the other problems.
It now runs but is rough sounding at normal cruise speed but is almost normal at WOT

The P1571 Desired Torque code has been there over a year and 3 people who have experience have tried to fix that, they all 3 decided it was something inside the transmission, that idea is out the window because I had to have a new transmission 2 months ago after the radiator puked the seal between the transmission cooler and the water compartment.
That was a mess, it filled the transmission with coolant and the coolant with transmission fluid. It was a pink foamy mess.
They removed the thermostat and ran water through it for over an hour before it was clean.
I now have a separate transmission cooler.

I have a P0342 that has also been there for a year, the only problem I have ran into with it is it sometimes takes longer to start

C1277 which is associated with the P1571

The P0102 seems to be a problem right now.that needs addressed.

I checked the plug voltage and the ground is fine, and the +5volt is fine bot the +12volte has no power. I tried a jumper wire to the plug and it did not help.
I did do a lot of wiring jumbling so I am hopeful it is a simple problem

I plan on replacing some vacuum lines that I know are brittle and checking the rest.
I put new plug wires on 2 months ago after one got into a header but it is due plugs so they will be replaced in a few days depending on how I feel.

At the moment I would be embarrassed for anyone to look under the hood. The PCM/TAC are sitting next to the battery and the fuse box is also wedged between the battery and coolant tank.

The car is my baby and i feel sick when it is not running good.
I have been known to wake up at 3am and think of something and go out and try it.

My last one is a C1222 RF wheel speed sensor.
I thought it was the wire so I fashioned a jumper wire to test and it did not work. It would appear that I actually have a bad speed sensor.
But the car has over 300,000 miles on it of which I put 200,000 and know it has not been replaced.

This video was 2 weeks ago

 

I am still having a slight miss at highway speed.
When running hard it is great,
I do have a P0342 which has been there for over a year.
This problem started with the bad wires going to the Throttle position sensor, I thought I may have fouled a plug so I pulled them all and installed mew TR55 gapped at .5
I thought ot may have been running rich but the plugs do not show signs of that. I had 1 with more black buildup I know it would be worse than the others because of a bad wire a month ago. It does not appear be bad enough to cause my problems and new plugs and wires did not help.

The pic on a single plug is what 7 looked like
the one with 2 plugs shows the bad one with one of the other 7

anyone have any other suggestions?
Thanks in advance