P2138 the lacrosse from hell

[ACEPA]

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

After three days of scanning and taking measurements got nowhere. The condition is difficult to replicate. Everything measures correct. Even with the voltmeter resistance and continuity. With P2138 code erased on startup no code. Slow acceleration no problem. The code kicks in only on fast depression accelerator when APP1 and APP2 for a split section go out of proportion or I can get P2138 at full throttle showing APP1 40% and APP2 90%. Checked all wiring and connectors live with no reading change. Baffled by the cause.

 

[ACEPA]

After three days of scanning and taking measurements got nowhere. The condition is difficult to replicate. Everything measures correct. Even with the voltmeter resistance and continuity. With P2138 code erased on startup no code. Slow acceleration no problem. The code kicks in only on fast depression accelerator when APP1 and APP2 for a split section go out of proportion or I can get P2138 at full throttle showing APP1 40% and APP2 90%. Checked all wiring and connectors live with no reading change. Baffled by the cause.

A new development I had the battery disconnected for 2 hours while checking wiring coming out of the bulkhead and now I get P2138 only when I turn on the ignition, if I errase thereafter can drive the car and it does not reappear. What a weird electrical system.

 

[ACEPA]

My P2138 saga continues if I deleted my P2138 code once the ignition was turned on for no explained reason I got to the point where if I would drive in a casual fashion it would not come back. I checked and cleaned all ground locations but all were in excellent condition. I elected to install a new battery after finding the voltage at 12.O volts and was showing 11.4volts battery from battery positive terminal to ECM housing and from power terminal to chassis connection point of 11.7volts. My readings now are
Battery 12.6 volts engine not running
Power to ECM housing 12.4 volts
Power to chassis ground 12.7
The problem having no errors on casual driving old battery disappeared and now with the new battery multiple P2138 errors occur again. I am no closer to solving the problem with a new battery, new throttle body and new throttle pedal and hours studying the wiring system.

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.

 

[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.

After three days of scanning and taking measurements got nowhere. The condition is difficult to replicate. Everything measures correct. Even with the voltmeter resistance and continuity. With P2138 code erased on startup no code. Slow acceleration no problem. The code kicks in only on fast depression accelerator when APP1 and APP2 for a split section go out of proportion or I can get P2138 at full throttle showing APP1 40% and APP2 90%. Checked all wiring and connectors live with no reading change. Baffled by the cause.

A new development I was reading ignition on 12.4 volts on the battery terminal but noticed positive terminal to ECM chassis voltage of 11.4 volts and 11.7 volts positive terminal to chassis ground point I installed a new battery because what appeared to be weak readings. All readings returned to normal
Battery 12.6
ECM chassis 12.4
Chassis ground point 12.2
Guess what the P02138 disappeared and returned as P0697.00. My ESP errors still occur but show this new code after battery replacement.

 

[richardnewton]

A new development I was reading ignition on 12.4 volts on the battery terminal but noticed positive terminal to ECM chassis voltage of 11.4 volts and 11.7 volts positive terminal to chassis ground point I installed a new battery because what appeared to be weak readings. All readings returned to normal
Battery 12.6
ECM chassis 12.4
Chassis ground point 12.2
Guess what the P02138 disappeared and returned as P0697.00. My ESP errors still occur but show this new code after battery replacement.

Are those voltages with the engine off, and all measured from the battery + terminal?

Those are big voltage drops and could be an indicator of a problem. Low voltage can cause a lot of random system errors. You really shouldn't have much of a voltage drop in that situation; It won't permit proper current to flow. Could be a problem with connectors, wires, grounds, equipment, etc. But connectors and wires are a first stop for simplicity.

If you have a heat-camera, that might show hot wires, connectors, crimps, or boxes that help you identify areas of high resistance or issues.

Battery cables that are not tightly connected, corroded, or failing can get hot to the touch after a long drive, for example. I don't know if that is a common issue on these cars. Regardless, the still problem could be downstream.

A few people here documented that a lot of the body grounds in the engine compartment corroded early. Maybe that is partly from excess paint?

We had a bunch of (different) random codes. What we did was find about a dozen body grounds, disconnect, clean the connector and body interface (sanding both corrosion and paint at the connections), reconnect. I think we had some grounds under the battery box but don't remember. And cleaned and reclamped the battery cables.

The best voltage drop test will be with the engine running and "most" accessories on. You should still be seeing over 13 volts from the battery terminal to different major grounding points (particularly when engine is running a bit faster than idle). Do a search on the internet to see how that is done.

Do you have the hybrid? If so, use extra caution for the super high voltage lurking and battery pack!

You can also check a guide for the code you see:

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/P0697/

The Chevy Terrain forums have a lot of 2.4 engine information (they don't have the hybrid model). Here is one thread but there are more:

P0697 Code what to do next

Hi, I had an engine MIL about 12,000 miles ago and it just disappeared all by itself. Just last weekend, it appeared again and disappeared after a few starts and drives. Also twice the Stabilitrac with reduce power appeared. I hook up My OBDlink MX with OBDlink app and it shows the code P0697...

www.terrainforum.net

 

[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.

An interesting development after installing a new battery the P2138 that appeared for ever has totally disappeared and transformed now into P697.00. I get P697 on startup always after erasing it drives for hours with no codes.I noticed driving the car the other day driving on a flat road the P679.00 came on once when hitting a small bump in the road or for no reason when cruising once. Some connection is bad or a wire is going open at wim.

 

[ACEPA]

P2138.00 A conclusion to my problems and be warned the you tubes videos can throw you off track. Following tech videos, I replaced the throttle pedal, replaced the throttle body. Replaced an aging battery. Checked all wiring ground and power connections still no success but getting serious discovered the ECM has a problem. Folks say the ECM is a rarely an issue in ESP reduced power module not in my case. I discovered TSP app 1 voltage was not following app two. Running my autel live scan on diagnostic mode on the TSP readings and a wire connected to the app 1 pin on the ECM plug on pressing the throttle to the floor discovered 0.5 volts difference throttle on the floor. As the throttle was pressed the difference between what my volt meter would read versus what the computer was reading. This was enough for the two potentiometers to disagree. Its sad an ECM takes 10 years to fail but that's life. Now I will ship the ECM off for repair. I feel I did the right thing at 300,000 kms to replace the items I did.

 

[richardnewton]

That was great troubleshooting.

I wonder what the ECM failure mode was. Water ingress? Failed solider joints? Other?

 

[G-775228]

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.

Over the last month my ECM in the hot weather just went crazy P2138 being the major fault

P2138.00
P0697.00
CO242.00
P138.00
P6A3.00
B1446-03