Multiple Issues but all basic fixes that the Parts cannon Failed again

Michael Diagnostician Holt, Michigan Posted   Latest   Edited  
Case Study
Trained By Techs
2008 Buick LaCrosse CX 3.8L (2 L26) 4-spd (4T65-E)
P0411 - AIR System "A" Incorrect Flow Detected
Theft Not Learned

Ok this vehicle came from a local car dealer and had alot of money already tossed at it for the p0411 code and the Theft not learned and horn inoperational. I started with the Theft not learned problem. I believe the code that was stored was a b3031 in the bcm which is where you access security data. When you turned the key on the last Pid under Vtd data would state key learn. First thing I had noticed was the key was new but aftermarket. First thing I needed to know is what this needed to be satisfied to exit learn mode and I simply found that in service information. It needed to see a proper key and when it finished the learn procedure it would automatically exit and the B3031 would become a history code. Well this one was a current code and from the pids in VTD it continuously was looking to relearn a key which told me this new non oem key was an issue. We went to the local dealer and had a couple keys cut and went through the learn procedure and that problem was cured. There is two versions of keys passkey and passkey + and if you get the wrong one as they did this is what you will encounter. So on to the next issue which had almost every single part for the secondary air has been replaced. I am familiar with when it performs the test which is on a cold start. This thing had new secondary air pump and control valves installed. First thing I needed was a diagram for how the circuit worked so I could test powers and ground. These relays are very easily accessed on the left strut tower with the large guage wired one being for the air pump and the other one with smaller guage wires for the control solenoid. First thing I needed to know is does the Air pump work which is also very easy to get to its right up front on the left side so I backprobed the power wire as the diagram indicates this is what is controlled as the ground is grounded all the time. I used my snap on solus edge scanner to bidirectionally control the Air pump relay. What I found was I had no power to the pump so I moved my lead up to the out put of the relay and still no power. So now I needed to check to see if I was missing anything from what the relay needed to work. I had power on the orange wire all the time and key on power on the pink wire with key on and just to make sure I loaded them with a 5 amp bulb which lit up nice and bright but not matching the load exactly so always have to keep that in mind. I tested the control wire from the Pcm and had control to the relay which proved I had a defective relay. Ordered a new relay and started the car cold and the secondary air ran and it passed its tests. I also ran it with bidirectional control and watched the airflow sensor to ensure I did indeed have airflow. So they put all that money into the system for a bad relay which was pretty quick to diagnose as a issue. Now if it would not have had a new airpump I would of wanted to use a power probe to make sure that the Air Pump worked and using an amp clamp to ensure not drawing excessive amperage. Now for the horn that was pretty quick and easy pulled a wiring diagram and on this car it controls the power side through a relay. The horns are on the passenger front corner and I backprobed the green wire and found when the horn button was pushed no power was present. So I moved up to the fuse box to and yes the horn fuse was good so I went to locate the relay and found it missing and noticed that their was one in the fog lamp spot but not all the way in and this car did not have fog lamps. Someone at some point had removed the horn relay and installed it in the wrong location. Relocated and all was well. These were all simple tests that had not been performed before tossing parts at the car. Diag fees were charged for each complaint and labor for repairs that were made. We must always perform diagnostics even on what seems simple because it could cost you way more than it needs to by guessing. Hope this helps 

William Diagnostician
Ashland, Virginia
William Default

Good processes for finding the root cause of the issues. I also see many vehicles like this that are on the receiving end of the parts cannon with no real diagnosis done. I blame both the techs and the owners/service advisors. Usually I find they won't charge for diagnosis and won't pay the techs for it, so they just do what they get paid for, which is throw parts at the problem! This is a

+1 Default Ð Bounty Awarded
Michael Diagnostician
Holt, Michigan
Michael Default

I agree there is no reason not to charge for diagnostics and techs should definitely be getting paid to do them as not only will it cost the customer less it will also build customer satisfaction and retention.

+1 Default Ð Bounty Awarded
Louis Diagnostician
Claremont, California
Louis Default

I wholeheartedly agree with you. Diagnostic time is good portion of my pay. I appreciate the fact that I work for an employer that knows the value of a good diagnostician, is willing to pay for my experience, and is willing to charge customers for my analytical services. That being said, I feel that a technician (not mechanic) should perform their due diligence and use their resources available…

+6 Default Ð Bounty Awarded
Louis Diagnostician
Claremont, California
Louis Default

And if you're gonna throw parts, at least use the correct diagnostic tools.

+4 Default Ð Bounty Awarded
James Technician
Plant City, Florida
James Default

If you use paragraphs in your post. it will become much more readable. I gave up halfway through.

+2 Default Ð Bounty Awarded