Hi guys, 05 c6 auto. 17k on the odo, no mods. Car went to dealership for a recall reprogramming. Drove the car maybe a Mile when reduced power came on and it instantly shoots a p0223. Went back to dealership, they replaced battery and throttle body with a Dorman. They billed the customer 3k, but couldn't figure it out. Then it went to a corvette specialist. They said it needed an ecm. They tried to replace but couldn't, said the ecm she got was junk, from flagship. Then the car came to me. (This is a customer car). I check it with my snap on solus. When erased the code instantly comes back. Pulled harness out of ecu and tb and ohmed. I get .4 to .6. So wires are good from tb to ecu. Tb is new. The ecu they tried to replace with didn't look to hot so I went to ecu masters and got another. Was programed with "plug and play" described.after key relearn, I tried that. Car wouldn't start, scan tool won't communicate, ignition switch wouldn't do anything. All sorts of weird bugs. Contacted the company and they gave me a new one. Said it sounds like that ones bad. Get the new one and it's similar but now I can communicate with it. No crank, weird ignition and every code an ecu can list is current. So. The only ecu that will run the car is the factory one. I did the key relearn to no luck on all ecus.I have recently re check wires, re did grounds. I get.2 Ohm on ground from bat to engine and other grounds. I replaced the tb harness pigtail and the only thing that has changed with the car is now it'll rev past 2k but still slow and reduced power. For sh#ts and gigs I got a tb from ebay and throttle pedal and same thing. I'm stumped. Everything I do points to a ecm and I have 0 clue why that's not working out with new ones. Wondering if I'm missing a step. I am a shop owner, we typically don't get stumped but man this ones getting me. I do have hp tuners if for some reason I need it. But this is all factory. Something tells me maybe the dealership messed up the map on the reprogramming preformed. Any suggestions would be very much appreciated

 

Worst case HP Tuners will work to tune code out. I had to do it due to turbulence in my airflow from my intercooler design.

 

A DORMAN THROTTLE BODY and now another new one off EBay for maybe $100.00 ??…OMG !!…that’s probably your problem…I would never use anything that has wiring and use a Dorman product but that's me !!…as a shop owner did you see what the conditions are for setting a P0223 in Alldata or whatever service info you use ??…it sets if ECM sees TPS 2 voltage of 4.725 volts or more for 1 second…with your scan tool are you seeing 5 volts (5 volt reference) on the TPS2 data PID…the 5 volt reference may be shorted to the signal wire…you should do a pin drag test on the connector…with scan tool you should see a little less than 1 volt with foot off gas and about 4.4 volts at WOT…you check the low reference ??…BTW do you use a labscope in your shop ??…for something like a TPS sensor it’s best to use one as a DVOM or even a scan tool will not see the rapid change in voltage…refresh rate is just too slow !!...you should be monitoring TPS 2 voltage going down the road preferably with a scope…since the C6 TB only uses 1 low reference wire vs 2 on the C5 I would expect to see a DTC for both TPS sensors if you were losing the low reference ground…if you back probe sensor ground with connector plugged in and ignition ON you should see less than 100mv’s...there is a TB available on Rock Auto sold by Standard Motor Products for about $671.79...they are a GM Tier 1 supplier...a junkyard would also be a good but cheaper source…lastly resistance checks isn’t the best way to check your grounds especially the resistance check you performed from the battery to the engine…voltage drop checks which is a dynamic test is the way to go…there are many YouTube videos on how to do a voltage drop checks…you would hook one lead of DVOM on battery negative and other lead on the block or whatever other ground you want to check…max drop is .5 volt but you should see less…when engine is running the lowest negative potential is on the alternator case and not battery negative.

 

thanks for the reply. i should have been more detailed. the tb and pedal from ebay was used "good". i have alldata and identifix and identifix was a joke for procedure but all data was good. it says 4.75 or more on the tps2 for one sec will make the cel. i did the test, tps2 has between 2.5v and 4.96, goes up and down, i depined that purple tps2 wire out of the ecu and still reads 4.96. which in all data's steps says to replace ecu. dorman tb came from dealership and they said the oem ones are discontinued. i haven't checked into it and didn't wanna throw an expensive tb on it when it seems its not even the tb to me. i just cant seem to figure out why all these ecus wont work on the car. low ref is exactly 5v. we do have a lab scope, i havent done a volt drop test but i will do that today i cant really drive it however because it wont move very fast. it will only rev to 2k while trying to drive.

do you guys know of a procedure for the ecu replacement? alldtata doesn't have anything besides this, which i have tried already
ECM Replacement
If the engine control module (ECM) is replaced, the following procedures must be performed:
1. The ECM Reprogramming-Refer to Service Programming System (SPS).
2. The CKP Variation Learn-Refer to CKP System Variation Learn Procedure in Computers and Control Systems.
3. The Theft Deterrent Programming-Refer to Programming Theft Deterrent System Components (RCDLR Setup) Programming Theft Deterrent System Components (Domestic) Programming Theft Deterrent System Components (Export - Including Canada) in Theft Deterrent.

thanks again guys

 

So your saying with your scan tool key ON TPS2 reads 2.5 volts with your foot off the gas and then to 4.96 WOT ??…my TPS2 goes from .94 to 4.39…at WOT the voltage should not go above 4.75…that is why it’s throwing that DTC…if your saying the purple TPS2 signal wire goes to 4.96 you’ve got a problem !!…it should be less than 4.75…under acceleration see what TPS2 does with your scope…how I check the TPS unplugged is check for the 5 volt reference…I then jump the 5 volt reference to the SIGNAL…the scan tool voltage should read 5 volts…you should have less than 100mv’s on the low reference....if wiring checks out as I mentioned you have a bad TPS sensor....the sensor pulls that 5 volt reference up or down depending on the TPS sensor and sends that voltage out on the signal wires.

 

no, it goes from 2.5 up to 4.96 all by itself. the scope shows up and down and im not touching anything. i can pull the purple wire out of the ecu, and still reads that way. so its like how can the ecu be reading any volts if that wires not even attached. cant be a cross in wires. has to be a internal fault in the ecu. i just got off the phone with ecu masters and they said try to relearn the security again. im gonna throw the new ecu in it again and try that and see where that gets me. and sorry, the tan/white low ref reads 8.7mv key on engine off. i mixed up your question. and i get a full 5v ref on the lt blue/black wire

 

Ok, watch the video on TPS sensors and potentiometers….the ECM puts out the 5 volts and the TPS sensors will pull up or down the voltage on the signal wire…the ECM is NOT putting out a signal voltage to the TPS…the purple wire is the TPS 2 signal wire…with the sensor UNPLUGGED and key ON you should see about 0.012 volts or so on the purple wire…if you see 4.96 volts on the signal wire it is SHORTED to the 5 volt reference !!…that’s your problem and that is why the signal voltage is jumping up and down by itself…you need to unwrap the tape and find it…if your are seeing 4.96 volts on that signal wire with the signal wire depinned I have never seen that….if you go into OBD2 generic with your Solus see if there is a TPS2 voltage data PID there and what voltage it reads…as far as the no comm if the 5 volt reference is ever shorted to ground it will put the ECM “to sleep” !!…the ECM is basically dead and with the key ON you probably will notice the MIL is not illuminated…did you notice any bent pins when you removed the ECM connector ??

 

sorry, again im not being too detailed. i understand how they work. so im watching the pid tps2v and its reading the 4.96v & 99%. i can depin the purple wire which would be the tb reading back to ecu and it still reads 4.96 on the pid. the actual reading of the purple wire with key on using a dvm is 1.29v. so how would the wires be shorted together if that wires not even attached to the ecu and the scan tool is readding that 4.96. no bent pins, and dialectric greese is added. i just ohmed the wires to see if i would get a reading between the tan/white and purple wire and its open line. so i dont belive its a shorted wire between the two. and the no comm was with the 1st ecu i tried. i have two reman ecus from flash masters, i will have to re try. i called them today to talk and they said to retry the second computer they sent. said maybe the rcdlr system might have not completed the process. they said, try to start the car, (which it wont crank with that ecu) then leave key on for ten mins, then off and back on for a total of three times. thats the relearn but then said somtimes it takes a lil longer between steps. and siad the lock light will shut off once its readdy for the next cycle. so ill try that next and see where that gets me

any more thoughts? thanks so much for the help

 

If the sensor is plugged in and you check with the scan tool and it reads 4.96 it should read the same with a DVOM probing that same signal wire…if you are seeing 4.96 at the ECM you should see the same voltage backpinning the purple wire and not 1.29 volts…like I mentioned I’ve never seen that voltage on the ECM signal wire with it depinne..if so looks like a new ECM…this is about all the help I can offer…GOOD LUCK !!

 

so update. replaced ecu with the flashmasteres, re did the relearn, and it started. however, throwing codes for low voltage on s1 and s2 lol. i checked 5v ref and nothing. put my dvm on the wire and pushed the connector in and got it back. depined c2 and re clamped the small connections back closed. re connected and got the 5v back, but guess what... same issue. inferiiating!!!! jumped the 5v light blue/black wire to the purple. nothing changes. it constantly jumps from 2.4 to 4.96 like clock work. every couple of seconds. jumped the 5v to tps1 and the volts go straight to 4.96 on the scan tool key on this testing was. the low ref is 8.6mv. 5v is 5.02.

now key on, dvm reading volts of the purple wire remains 1.29v and the tps1 reads 3.7v witch matches the scan tool. not the tps2 tho. thats a differnt reading from dvm to scan tool. unplug the tb and tps2 still does the same thing, and tps1 drops to 0 on the scan tool, but the dvm reads both tps1 and tps2 wires under 3mv...

stumpped

 

With the connector plugged in and back probing either TPS1 or TPS2 the signal wire voltages with a DVOM should match the scan tool…try going into generic OBD2 with your scan tool and see what the TPS voltages read there if you see them…data PIDS there can’t be “substituted”…don’t know if you are familiar with “substituted values” on a scan tool ??

 

global cant substitute and sensors value, checking that rn

 

Exactly !!…don’t know if I ever looked for TPS in Generic ??

 

absolute throttle position% 100
absolute throttle position b % 100
relative throttle position% 89.8
comand throttle act.control % 1.2
accelerator pedal position d % 10.2
accelerator pedal position e % 20.4

 

No voltage ??….just percent ??

 

these values do not change weather tb is plugged in or not

 

These are my figures in Generic OBD2 with my Verus Pro…top pic is idle and bottom is throttle WOT !!…my figures do change.

 

Odd !!…this is what the ECM is seeing !!

 

i have a snapon verdict i will try and see what global shows on monday. i also have hp tuners at my disposal

 

problem fixed! I have a video to show the issue, purple wire out of ecu, ecu reading 4.96v. If you wanna see that. while doing all these test i noticed somtimes it would run rough and then id mess with c2 connector and it would remdy the issue of rough run. So as a last ditch effort i took the c2 apart, and the individual connectors were very loose on the pins. I took all the wires out, pinch them back tight with a set of wiring crimps and waalaa. Runs great. No cel, and all is well. Thanks guys. Till this day I'll never understand the results in all the test I was doing. Why on earth a loose or disconnected pin would show 4.96v even tho it was unplugged. No clue. But she's all good now. Voltages read good etc.


On this you dont have to put any pressure just close the crimps and it just so slightly brings the connector back to tight

Here you can see how little it collapse the connector. Just enough for a tight fit