update post 48 - issue seems to be solved. More driving to do...

After researching similar threads for the last several days and learning quite a bit about this issue, I wanted to post my car's situation so see what you gurus out there think.

A year or so ago my car went into REP with engine light. After a shut down and restart it seemed fine but the check engine light stayed on for a handful more startups and eventually went away (I have read that is normal). This happened probably a half dozen times then eventually stopped.

This past weekend it came back, but was much worse. The car was shaking at idle and even stalled at idle a few times. Within a minute or two after restarts, it would fall right back into REP mode and was not driveable. It would top out at 25 mph max which would eventually begin to go backwards and lose what power it had left vs last year where i could still get it up to 60 mph + or so and there was no idle issues etc (throttle was delivering more power).

So, I got it towed home, did a ton more research and decided to buy my own code reader. Picked up a craftsman 47156 from sears for like $60 and decided to take a look, then clear the codes. Codes below:

P0172 - Fuel trim system rich
P0175 - fuel trim system rich
P0068 - Throttle body airflow
P0101 - MAF sensor performance
P0106 - MAP sensor performance
P060E - Control module throttle position circuitry performance
P2135 - Throttle position sensors 1-2 not plausible

After the code clear, I took her around the block with no issue. Will go for a longer ride this afternoon and be sure to bring the code reader along. My assumption is that I should wait until it happens again and immediately read the specific codes that trigger. Does that sound right? Additionally, I do have one tire pressure sensor that occasionally acts up (will all the sudden read extremely high or low then goes back to normal). My plan was to wait until I need new tires and replace all 4 since they are old. In my forum research it appears some people believe the tire pressure sensors can create the REP issue while others say absolutely not. Thoughts?

Since every culprit for the issue pulled a code (TB, MAF, MAP, Throttle position) I have no clue what I should do.

Lastly, what the hell is Fuel Trim Sytem Rich?

Car is relatively stock- 2005, corsa sport exhaust with x pipe, calloway honker, MN6

Any information would be greatly appreciated. Hoping this won't be thousands to get taken care of. Thank you all for responses and recommendations .


Best,
Mike

 

Is car stock or not?

Fuel trims are automatic adjustments to fueling that the computer does based on O2 sensor readings to adjust fueling back to 14.7:1. The ECM can normally calculate things well enough so that only a few percent adjustments ("fuel trims") are needed.

If the computer is having to make very large adjustments, say 30 or 40%, then it can throw a code saying that something is wrong because there's no way it's calculations are off by that much on a more or less stock car.

Yours is saying it's extremely rich and having to make large adjustments to counteract that.. the adjustments are beyond what is considered normal.

That many codes makes me wonder if it's a battery/voltage/ground issue.

 

Maybe even the dreaded spark plug wire popping off syndrome..

 

I did change my battery out a month ago or so? Maybe some of the codes were from the old bad battery? It had a bad cell. I highlighted info on my car above. Calloway honker and corsa sport with x pipe. Otherwise stock.

So do we think there is a real fuel issue or could just be triggered from old battery or REP? Best to just wait until something happens and read the new codes?

Thanks!

 

Just check all the spark plug connects?

 

Yeah, they can pop off the coil side and come loose on the spark plug side, so you may have to pull the fuel rail covers to get a good look and give them a push to check the fit.

 

Don't think this one is a spark plug wire. That's not what I see in these codes. I do see the ECM lost its way on fueling. The codes that are primary here, (started it all) I believe, are P060E and P2135. These two codes have a relationship with drive by wire and the TPS. These two systems have NO tolerance programmed in. When the ECM loses its signal with the driver requested throttle position it will immediately revert to REP. In the meantime, BC so many other secondary signals are being inputted at the same time, the ECM recognizes those as momentary faults and records.

The fuel trim codes, MAP and MAF I see as secondary. The primary faults here are the Codes mentioned above. I would be looking at the throttle signals (both send/receive) and the TPS.

Edit: I probably should have put in here some simple things to do. Easiest things - Check the electrical connections at two places. The Fuel pedal signal connector (This is the one that is unplugged for the famous Vitesse controller), and the connector to the throttle body motor. Unplug them, clean with electrical contact cleaner plug back in. These send/receive units use "sweep Rheostats" on the same order as the fuel sender unit. Over time they can wear dead spots. It that is the case, they'll need replacing. BTW - Should do the unplug/plug cleaning with batt disconnected.

 

Thanks for all the info there. I had been looking around the other day and can't find any directions/pics of how/where to unplug the suggested connectors. Anything you have would be great!

Also, at this point should i just wait until something happens to start messing with everything? Given that I cleared all codes today...

 

Check your ground connections. I cannot stress this enough. A loose or corroded ground will reek havoc on your electrical system. I have experienced this first hand. The loose ground was causing my car to do exactly what your car is doing.

Also, check your starter solenoid terminals and make sure they are not broken inside of the bakelite housing. This can cause major electrical problems. I have also experienced this first hand.

 

First, there is nothing wrong with doing all of the suggestions you're getting here. Checking wires, grounds, connections, all good, easy, things to do at no cost, just some time.

I am interpreting the codes you've published and it leads me to the drive by wire system which is intentionally sensitive with no fault tolerance built in. There are two distinctive groups in the codes, one cause and the other effect and this is very common in fault diagnosis. The fuel trims, MAP and MAF codes are all effect. The cause comes from the P060E and 2135.

I believe you're going to eventually find a hard fault either in the TB motor or the sender side, the gas pedal sender. The sender connection is at the gas pedal. The TB connection is at the throttle body. It's the large plug into the TB side. BTW, the TB casting where the electrical conn plugs in is the TB motor. this is likely the failure point and I am pretty sure neither is serviceable.

The send/receive failure is obviously intermittent. If a dead spot is developing, unfortunately, there are times when electrical connection will be constant, then you'll catch a humid day or some other anomaly and the signal will be lost. If it is a wear failure developing, it will get worse over time.

Each unit (TB input signal; Sender unit output signal) should have a static electrical test with an ohm range and/or V range which can lead to determining which unit is failing. I don't have access to that info.

BTW, I expect since you've cleared the codes, everything is back to normal, you can always just drive it, when the failure occurs again, read the codes. I expect that you'll always see P060E and/or P2135. After that, any other grouping of codes might appear or the same as above.

 

Another possible issue..
There is a service bulletin about the P2135 code, covering model years 2003 to 2006.
A badly crimped or broken wire under the insulation at the TB connector
link
https://www.corvetteforum.com/forums...-problems.html

 

Now you're talking! This is a strong possibility. The connector mentioned is one of two I was directing the OP to. GOOD CATCH!!

Mike - If I were you, I'd follow the instructions in the attached link that extrapilot posted above. Stick with us here and we'll help you through it.

 

Mike,

If we find this is your problem, I believe I've found the pigtail mentioned in the link from extrapilot. The TSB warns of problems, but I am guessing it's BC of dissimilar wire material. Anyway, a little ahead of ourselves, but keep this link if need be.

http://www.ebay.com/itm/LS2-LS3-LS7-...FUk8AP&vxp=mtr

Another possibility is to look for a TB harness on Ebay if the broken wire is your issue.
In the TSB, it describes a wiggle test. This would be with the engine running and you'd be trying to duplicate the CEL P2135. That is helpful and I can guide you through it.

 

Ok so here is my update. I decided to be brave and "drive" in to work this morning. As I mentioned, codes cleared yesterday. Got about 2 miles and first thing to pop up on the DIC was Service traction control. Within a minute or so cam REP mode so I pulled over in order to check codes. Again the car was shaking at idle. Turned it off, plugged in my code reader then went to turn on accessory mode....This is when something NEW happened. The car could not detect my key fob this time? I had to put it in the slot in the glove compartment in order to get the car into accessory mode for the code reader (there is nothing wrong with my fob and battery is relatively new). Now it was time for the codes.

As BlindSpot mentioned - I should see P060E and/or P2135.....

Per usual I am not that lucky. I got the following:
P0068
P0101
P0106
P0172
P0175

Once I cleared the codes I was able to take my key fob back out of the glove compartment and the car read it normally. Started right up and headed back toward home. Car went back into REP 5 min later and I went through same process. It did stall while idling at a light on the way home when it was not in REP mode.

I guess I will need to start process of elimination based on posts above? Part of the issue is I dont know where half this stuff is.

 

MAP is on the top of the intake, right near the TB

MAF is near the air filter

Without having a higher end scanner on it to see what all of the sensors are reporting we are guessing at what it could be. The good news is you can replace the MAF and MAP for under $100 total... so it's probably not a bad idea to just replace them to eliminate that possibility.

 

I think this is my plan of attack in order of what I believe to be most important (correct me if I am wrong)

1. Clear codes, turn car on, wiggle TB connector to see if it triggers code

2. Check connections at fuel pedal signal connector (I looked near the pedals but not sure where this is located. any pics?) and TB connector - Based on above I should disconnect battery then pull these connections and clean with electrical contact cleaner

3. Check spark plugs for snug fit

4. Check starter solenoid terminals to be sure they are not broken inside baklite housing (where is this?)

5. Check ground connections - this link should be helpful (https://www.corvetteforum.com/forums...locations.html)

I do not have anything to measure ohms etc... at that point I may just have to give up, pay the ridiculous towing fee and have Rick at RKT Performance take over.

Please let me know if the above plan of attack is out of order or missing things etc. You guys have been awesome. Very thankful for the help.

 

Sorry, I'm just catching up here. Yes, it looks like a thought out plan.

The MAP sensor coincidentally, is on the same harness as the TB motor.

Do you know which harness? It is a small U shaped harness starting at the throttle body connector. Do this first! Make sure the car is warmed up, op temps as you want to be in closed loop. Have the scan tool set up, make sure you've cleared all codes. If someone else can be in the car, have them raise rpms. Doesn't need a lot, just off idle. Then wiggle the U shaped harness, see if you fall into REP. Be careful, you're close to the serpentine belt. Record the codes. I'm still in the camp that you're not done with P2135.

 

As a follow up to Blinspot, and he has great advice here, your trying to find a wire that is in the wire harness that could be broken inside the insulation of a individual wire and or a bad crimp in the metal pin on the wire end that goes in the back of the connector. You said in your post that you would try wiggling the connector, as this may not be what you should actually do in attempt to recreate a disconnect, and throwing the codes. Also try to get as close as possible to the connector at the TB, give a tug and wiggle the actual wires that you will see leading into the back of that connector.
Sorry how long this was but just trying to be clear on this subject..

 

Ok so wiggle the wires not the actual connection. Got it. I will be diving in to this likely tomorrow afternoon and will update accordingly. Stay tuned.

 

pull the air filter assembly and look inside for something blocking air flow, if clear you likely need a new throttle body, look in the parts section for a used one