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Discussion Starter · #1 ·
2011 Chevy Malibu LT, 2.4 L9, 160k
This issue is causing me to lose sleep. This is my son-in-laws car. We had the trans rebuilt in Feb 2021, the second time in 4 years. A week after picking up the car, the car started started to throw a P2135, Throttle Body Sensor. Then like normal it will go into limp mode and the traction control warning would come on. Searching the net show lots of these. I replaced the Throttle Body using a cheaper Amazon unit and immediately it threw the code again. I bought a GM authorized one (this model you have to replace the entire Throttle Body, not just the sensor) and it threw the code again. I have gone threw the Throttle Re-learn, both manual and using my scan tool. I went through all of the wires and connectors. Unwrapped them, checked them, re-wrapped them. Saw somewhere that the Negative Battery cable forming bad ground caused such issues and replaced it.
Things that I have noticed:
  • Almost always happens within approx 1 mile of initial driving
  • The Traction Control Code says 'unknown serial number'
  • Always happens at lower speed, usually during take off.
  • I would relearn, reset the codes and drive it for 5-7 miles and it would work. I would give it to him and it would throw the code the next day. He DOES drive like a little old lady. The code HAS been thrown on me. To my memory it was always always at take-off or slow speeds, like rounding a curve in the subdivision.

One time, I reset the codes, did a throttle body re-learn and when I happened, I just cleared the code and continued driving. I drove the car for a week, put on 160 miles, dozens of stops and starts and one trip was 90 mile highway/city with multiple stops. Temp range outside went from 25 to 60. All the while I had my scan tool connected and I was recording the data stream each time I went out (no matter how short a trip) trying to capture when it happened. It never did it. I figured it was possible that after doing the TPS re-learn was set, it throws the code, you reset it and keep driving while it learns (something I read online as possible). I gave the SIL back his car. Three days later, it threw the code again. Same thing, P2135 with traction control in limp mode. I tried to replace the accelerator pedal (which has its sensor, again because of a possibility I read). This was a GM part. Each time I plugged the accelerator pedal in I would get a P2137 dealing with sensor 2's voltage being 2 low. Watching the datastream, the senor was putting out and initial .25 volts at idle (increasing as you push down on the pedal), but the other pedal was putting out an initial .47v. I don't find any form of accelerator pedal re-learn. I am at a lose.

I haven't taken back to the trans shop because that traction control/power lose mode is common when codes are thrown and I can't prove anything is wrong with the trans. He is unemployed right now and the whole thing has already cost me a lot of money. Am I missing something? Could it be the computer needs to be re-flashed with more current code and doesn't tolerate the wider ranges in the TPS or accelerator pedal? Could it really be the traction control screwing up in the trans causing the TPS to throw a code (something else that I appear to see might be possible) In which case it would be the trans. When the Traction Control kicks in and it can't identify the trans serial number, would that cause it? I have deliberately taken it it for a ride over every bump and speed bump I can find and nothing happened. I am tired of read articles. Anyone have anything concert that could help me?
 

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Are you able to read the U, B and C codes ? Could be one if there pointing to a problem.
Traction control issues commonly are due to wheel sensor issues causing it to randomly kick in and power will be reduced to control wheel spin.
Have you cleaned all the module connectors with a electronic cleaner / lubricant ? These years are prone to fretting corrosion in the connectors causing oddball or erratic issues.
Just a few more ideas to think about as we aren't techs in a shop seeing stuff all the time, full scan of all 4 code families is most important chasing down weird issues.
I had a MAF sensor running on the edge of setting a failure code and found it as my scan tool can read the frequency it was running at and it was at the edge of normal range. Had me scratching my head for a while.
 

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Discussion Starter · #3 ·
Yeah, I my scan tool will read all of the codes. I have a launch CBP129 scan tool. Always the same 2 codes with only the P2135 being the primary and traction control serial number (I forget the code at this moment). I didn't want to di-electric all of the plugs but I went over them pretty good and pulled and moved the wiring roughly while watching the datastream. I couldn't get it to change at all no matter what I did by hand. But could the traction control issue be primary causing the TPS to error? Having the trans rebuilt could just be coincidence or it just released an issue that was going to happen anyways. Just trying to beat my head before I call the trans shop again. Can't figure out why the accelerator pedal sensor replacement kept through out the low voltage code immediately. It was working, just at .25v verses .47v for the original at idle. This would point to a computer calibration issue, but I find no pedal reset method, so it has to be burned into the computer. I haven't gotten a second pedal to verify.
 

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This is what Alldata says for my old '09 2.4 . I'd spend the $30 for a subscription for yours as it's got diagnostic data and testing info. This is just a sample for your code.

Conditions for setting P2135

The difference between the TP sensor 1 and TP sensor 2 exceeds a predetermined value for more than 2 seconds.
P2135
  • The system voltage is more than 5.23 volts.
  • The ignition is in the Unlock/Accessory or Run position.
  • DTCs P0120, P0220, P0641, P0651 are not set.
  • DTC P2135 runs continuously when the above conditions are met.

Circuit/System Description

The throttle actuator control (TAC) system uses 2 throttle position (TP) sensors to monitor the throttle position. The TP sensors 1 and 2 are located within the throttle body assembly. Each sensor has the following circuits:


  • A 5-volt reference circuit
  • A low reference circuit
  • A signal circuit
Two processors are also used to monitor the TAC system data. Both processors are located within the engine control module (ECM). Each signal circuit provides both processors with a signal voltage proportional to throttle plate movement. Both processors monitor each other's data to verify that the indicated TP calculation is correct.
 

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The issue has been happening to me as well, I've had my car just short of 2 months it actually has LITERALLY giving me nightmares I took the card at you different mechanics and before I done a ton of research to figure out what could actually be going on both my throttle body and throttle pedal are new the first mechanic did a complete rewire to the throttle body because it look like the pigtail this loose this did not help either it would throw me back down into limp mode it will only drive for a couple days before doing the same thing again however after I took it to the second mechanic and he tried all the things the first mechanic tried minus the rewiring putting another throttle body to it and the same codes kept throwing up and he accidentally bumped his elbow against where the wire harnesses connect to the computer this is where my problem in lies I have not had issues after thoroughly cleaning where the connector goes on to the computer itself when I say cleaning I mean taking high pressure air and blowing the dirt and such out I've now been able to drive for more than five days and not had a single issue I hope this helps
 

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Cleaning means spraying a electrical contact cleaner into the connectors.
Just unplugging / reconnecting a connector will semi clean it. I keep a can of DeOxit in my garage at all times for more than just vehicle stuff.
I'd spray those connectors with a proper cleaner and be once and done myself. Good cleaner will help ''seal'' metal contact points in the connectors from additional issues.
 

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Discussion Starter · #7 ·
I have intentions of doing a through cleaning in a few days when my wire brush set comes in. Its the last think I can try. BUT, dealing with fretting. I see SEVERAL posts and a few service bulletins out there from GM about this, but read conflicting advice. In the below service bulletin, you can see they are using Dielectric grease INSIDE the connector. The picture is clear and it even looks like one of the computers. Read read other things and they say NEVER put the dielectric in the connector and go through reasons xyz or some link to a post. The point they make are valid, but in MANY services bulletins, GM is doing it to stop fretting they seem to have often of. So I will clean the TPS connector and Connector 2 of the ECM and use light Dielectric grease like the picture and see what happens.

0492ba86-2b3c-4e7f-84c3-db21633d2933_My+Boot+Camp+printed+document-1.pdf (justanswer.com)
 

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2011 Malibu LTZ 3.6L V6 Red Jewel Tintcoat
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You may not want to use any wire brushes on the terminals. If even a single wire breaks off (they commonly do), it could get itself into a position that would cause a short circuit.

The instructions I've seen are to use a plastic brush with 1" bristles to clean with the DeOxIt (or other cleaner). Some instructions say to use the same brush to help push the grease down onto the terminals. I'm not sure about that part, though.
 

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Discussion Starter · #9 ·
Okay, this is the final post. After several months with this issue, that last service bulletin was the culprit. I removed both connectors from the ECM. Blew both sides out with canned air. Used a standard electronic (NOT electrical. It has to be made for electronics or it can melt the plastics) contact cleaner on both sides made by CRC. Let it dry. Then used some of the DeOxit recommended by repairman54 above. Expensive little spray at $18 for 5oz, but if they use it on guitars (it is sold in music stores also), then it I would trust it. It does not dry. It leaves a little slick coating on the connectors. I forced sprayed it into both sides. I let it 'dry' 30 min or so. Then I followed the GM Service Bulletin #09-06-03-004E (0492ba86-2b3c-4e7f-84c3-db21633d2933_My+Boot+Camp+printed+document-1.pdf (justanswer.com) Use THIS image. The others I found online are B&W and you cannot see the connector with the grease on it as well as this image. I put some of the CRC di-electric on a 1/2 inch brush. (I tried a 1", but it did not work very well. The brush I used was just a disposable rolled steel paint brush you buy in bulk from Harbor Freight, nothing fancy. I smeared it around in a THIN coat on the male side. I just dabbed it on the female side so it was lightly in the holes and wiped up anything else. I did the SAME thing to the throttle body connector. If you don't know which connector, the bulletin says all you suspect. I reconnected everything. When I reset the Throttle body relearn this time, it didn't throw the code. Originally the code was thrown 100% of the time after I did a TBS relearn (and I did that 20-30 times over the months). He has driven the car many times and so far all is good. With his gentle foot, the max he had been able to drive it before without a code was twice.

So if you are getting the car (and this is almost ANY GM vehicle mid-2000's to now) getting a DTC intermittently, this may be the solution. It is usually the ECM connector, but I read it happens to the PCM, the trans connector, the accelerator peddle, and the brake sensor. This is GM's fault for using low grade wiring and pins in the harness and not sealing them at least. Hopefully this helps someone else out.
 

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Thanks for posting a solution.
Fretting corrosion can happen in any connector even though those weatherpack connectors seal pretty well.
I now hit any connector I separate with the DeOxit before it goes back together.
 
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