P2138 the lacrosse from hell

[ACEPA]

My 2011 2.4 lacrosse started getting error P2138 and EPS warning a year ago. I should over ride the soft error by turning off the ignition and restart the car. Slowly the situation got worse and worse. I used the new Antel scanner for diagnostics and purchased throttle pedal and a new throttle body unit. I can't prevent error the P2138. I clear the the code the code and as soon I use the the pedal a and the P2138 appears immediately again.
If I clear the P2138 it returns within in 20 seconds. So terrible that I can't use the car yet the ECU appears to read an electrical problem.

 

[richardnewton]

Here are some diagnosis steps with links of schematics and diagrams.

https://charm.li/Buick/2011/LaCrosse%20FWD%20L4-2.4L/Repair%20and%20Diagnosis/A%20L%20L%20%20Diagnostic%20Trouble%20Codes%20%28%20DTC%20%29/Testing%20and%20Inspection/P%20Code%20Charts/P2138/

 

[cosmicjazz]

Did you do the relearn for the throttle body after replacing it?

 

[ACEPA]

Yes I did. Two conditions confirmed I learned today that if I errase and park the car next morning as soon as I turn on the ignition the P2138 is there. Today's observations driving with my Autel scanner live and P2138 erased if I very careful press the throttle pedal very slowly it does not trigger the P2138 error yes if I pump the pedal down fast about 50% it triggers an error showing APP1 at 22% and APP2 at 31%. This is the reason for the ESP error disagreement on the throttle pedal position. With a new throttle body and new pedal. The tricky part is to know the root cause. At standard idle everything looks perfect. Today I had to reset P2138 at every traffic light manually because every movement demanding acceleration turned on ESP and P2138. What is cause ?

 

[02LTD2.0]

We're the replacement parts OEM or aftermarket?

 

[cosmicjazz]

Yes I did. Two conditions confirmed I learned today that if I errase and park the car next morning as soon as I turn on the ignition the P2138 is there. Today's observations driving with my Autel scanner live and P2138 erased if I very careful press the throttle pedal very slowly it does not trigger the P2138 error yes if I pump the pedal down fast about 50% it triggers an error showing APP1 at 22% and APP2 at 31%. This is the reason for the ESP error disagreement on the throttle pedal position. With a new throttle body and new pedal. The tricky part is to know the root cause. At standard idle everything looks perfect. Today I had to reset P2138 at every traffic light manually because every movement demanding acceleration turned on ESP and P2138. What is cause ?

What did the plug to the throttle body look like? If it’s dirty or corroded it would causes a bad connection also check if you have a broken wire in the plug

 

[ACEPA]

Af

We're the replacement parts OEM or aftermarket?

After market

 

[ACEPA]

What did the plug to the throttle body look like? If it’s dirty or corroded it would causes a bad connection also check if you have a broken wire in the plug

I will check and have a feeling the issue is at the throttle body and not the new throttle pedal

 

[ACEPA]

Did you do the relearn for the throttle body after replacing it?

Follow the process of three rapid presses in the throttle pedal it fails immediately. Looking at the live Autel readings
TPS
APP1 is 0.94V
APP2 is 0.46V
Throttle position ignition on at zero both APP1 and APP2.
Depression of the throttle slowly shows both positions within 2% of each other.
Rapid movement and APP1 and APP2 position can differ by 15%
This is my problem what causes disagreement in the throttle position at rapid movement only?

 

[HotZ28]

Af

After market

Bingo!

 

[ACEPA]

Bingo!

I would agree but interchanging the old throttle body and throttle pedal on live data shows identical measurements. All wiring appears fine. Live scan data implies everything is in the correct position but its not. A new observation today was ignition on pedal on the floor the throttle body flap is not opening fully. I gather that instruction comes from the ECM.

 

[richardnewton]

I like the aftermarket idea too.

The 2.4 changed several times after 2008 and you might have a part designed to earlier spec but mislabeled or confused. There are plenty of documented cases with: the timing chains, actuators, and high pressure fuel pumps; all very difficult to diagnose.

I would bet the throttle body but who knows. Try swapping 1 of your old parts to see if that is it. If not try swapping just the other part.

Here is a fuel pump example case

Case study - aftermarket HPFP will NOT work properly on...

Interesting case study showing why aftermarket high pressure fuel pump (HPFP) may not work on 2.4L engines. Need OEM. We see some ECM logic, graphs of low & high pressures (desired & actual) and fuel trims, scope readings of the pump, etc. The pump & ecm apparently changed "shortly" after 2010...

www.terrainforum.net

OEM engine parts from the dealer matched to your VIN are the best bet IMHO. Ask parts desk for a discount and you might get 15% or so.

 

[ACEPA]

I

I would agree but interchanging the old throttle body and throttle pedal on live data shows identical measurements. All wiring appears fine. Live scan data implies everything is in the correct position but its not. A new observation today was ignition on pedal on the floor the throttle body flap is not opening fully. I gather that instruction comes from the ECM.

I read today that some cars have a fail safe that with ignition on only, car not running the ECM does not allow the throttle flap to open fully with full pedal. Is that the case with the Buick Lacrosse? Does anyone know this as fact ?

 

[ACEPA]

I

I read today that some cars have a fail safe that with ignition on only, car not running the ECM does not allow the throttle flap to open fully with full pedal. Is that the case with the Buick Lacrosse? Does anyone know this as fact ?

To my helpers what is so strange with no P2138 'cleared' when I turn the engine off. Turn it on again within 30 minutes reduced power is there again P2138 without touch a thing, yet all the live scanned values are to the book.

 

[HotZ28]

Is the engine Turbocharged? If so, try one of these in the links below.

More Information for GM GENUINE 12670834

More Information for HITACHI ETB0070

 

[jeffbazell1]

I

I read today that some cars have a fail safe that with ignition on only, car not running the ECM does not allow the throttle flap to open fully with full pedal. Is that the case with the Buick Lacrosse? Does anyone know this as fact ?

Interestesting. Yesterday I had my 2018 Lacrosse in 'service mode' and when I pushed the accelerator there was no sound coming from the throttle body area, so I assume the throttle butterfly does not operate with engine off but ignition in 'on' or 'service mode.' My Cadillac and Subaru both responded but not this Lacrosse. hmmm...

 

[ACEPA]

Yes the ECU is a control freak ! I noticed testing my car using live data ignition on with rapid floor presses I could get APP2 to read 90% and APP1 to read 60% hence my P2138 code but still not sure of the root cause. With the ignition engine at idle on all voltage readings are to book specs and on rapid presses there are no voltage spikes or drops. On Friday I will do a full sweep of throttle wiring to ECU using a volt meter.

 

[ACEPA]

Yes the ECU is a control freak ! I noticed testing my car using live data ignition on with rapid floor presses I could get APP2 to read 90% and APP1 to read 60% hence my P2138 code but still not sure of the rootcause. With the ignition engine at idle on all voltage readings are to book specs and on rapid presses there are no voltage spikes or drops. On Friday I will do a full sweep of throttle wiring to ECU using a volt meter.

 

[ACEPA]

Cars are not manufactured to last years.

 

[HotZ28]

Cars are not manufactured to last years.

A better way of saying that would be; Newer cars are not manufactured to last for years like they once were.