06 Lacrosse CX 4T65E tranny, 2nd gear starts
Senior Member
True Car Nut
Joined: Dec 2018
Posts: 3,239
Likes: 1,597
From: Flint, MI USA
An update for the group.
I read several references to Dave, a tech at Triple Edge Performance and a primary source of knowledge specifically on the 4T65E. I emailed my issues and we engaged in a back and forth of a few emails. Great guy for sure! At this stage, he is in agreement with my transmission shop that the problem is either in the PCM or outside the transmission and likely the wiring. As long as the PCM is commanding the correct gear, it is safe to say the transmission is doing its job. He went on further to say he'* seen several occasions where there is a damaged wire inside the main wire harness under the air filter housing, either from a poor crimp on a terminal, wire break inside the insulation, etc. They don't throw a code but give the appearance the solenoid is at fault. This was in actuality the next step for us and Dave just reinforced what we thought.
Someone else made the recommendation to swap the new throttle body purchased a few months ago with the old one, which we did. We then also pulled the wire harness connector to the transaxle case, cleaned the connector on the case and the harness, applied some dilectic grease and reinserted. Did the same actually with the connector and cable leading to the throttle body. Surprisingly, although I haven't made any long drives, I haven't had any issues with the downshift to 1st. Also, haven't been out on the freeway to test between 3rd and D.
The transmission shop has a relationship with a connection to ATSG and indicated they would reach out to discuss. I told him I would attack things from the Buick side.
Called Buick mainly looking for TSBs and any kind of history of customers with this same issue. The rep indicated I needed to have an authorized GM servicer perform a diagnostic before they could do anything. When I tried explaining to the rep that with over $3,000 in transmission repairs, even the purchase of aftermarket parts would surely have provided enough royalty back to GM to more than cover a few times over the cost of a diagnostic. She then recommended going to my local authorized servicer and see if they would help. When I proposed getting the diagnostic done, then what could they do? She said they could make some "concessions". A 17-year old car with no remaining warranty on ANY part of the vehicle, what concessions ?!!?? You gonna give me 2% discount on a brand new GM vehicle
. Haha.
Well, I went down to the local GM dealer, talked with the parts manager who has access to TSBs and was able to get a few, took them back to the transmission shop for their thoughts. If I get the diagnostic done they can run checks to see if the PCM is updated to the latest firmware update, but there would obviously be a separate charge for the re-programming.
For the time, I'm good but at this point will look to target new harnesses. An AC Delco harness connecting the transaxle case and several components runs $230, not including installation. Since that is where the problem seems to be isolated, for the peace of mind and to rule out one less item, probably a good investment. I'll report back if we glean anything further on this.
Thanks again to everyone for the assistance and support.
I read several references to Dave, a tech at Triple Edge Performance and a primary source of knowledge specifically on the 4T65E. I emailed my issues and we engaged in a back and forth of a few emails. Great guy for sure! At this stage, he is in agreement with my transmission shop that the problem is either in the PCM or outside the transmission and likely the wiring. As long as the PCM is commanding the correct gear, it is safe to say the transmission is doing its job. He went on further to say he'* seen several occasions where there is a damaged wire inside the main wire harness under the air filter housing, either from a poor crimp on a terminal, wire break inside the insulation, etc. They don't throw a code but give the appearance the solenoid is at fault. This was in actuality the next step for us and Dave just reinforced what we thought.
Someone else made the recommendation to swap the new throttle body purchased a few months ago with the old one, which we did. We then also pulled the wire harness connector to the transaxle case, cleaned the connector on the case and the harness, applied some dilectic grease and reinserted. Did the same actually with the connector and cable leading to the throttle body. Surprisingly, although I haven't made any long drives, I haven't had any issues with the downshift to 1st. Also, haven't been out on the freeway to test between 3rd and D.
The transmission shop has a relationship with a connection to ATSG and indicated they would reach out to discuss. I told him I would attack things from the Buick side.
Called Buick mainly looking for TSBs and any kind of history of customers with this same issue. The rep indicated I needed to have an authorized GM servicer perform a diagnostic before they could do anything. When I tried explaining to the rep that with over $3,000 in transmission repairs, even the purchase of aftermarket parts would surely have provided enough royalty back to GM to more than cover a few times over the cost of a diagnostic. She then recommended going to my local authorized servicer and see if they would help. When I proposed getting the diagnostic done, then what could they do? She said they could make some "concessions". A 17-year old car with no remaining warranty on ANY part of the vehicle, what concessions ?!!?? You gonna give me 2% discount on a brand new GM vehicle
. Haha.Well, I went down to the local GM dealer, talked with the parts manager who has access to TSBs and was able to get a few, took them back to the transmission shop for their thoughts. If I get the diagnostic done they can run checks to see if the PCM is updated to the latest firmware update, but there would obviously be a separate charge for the re-programming.
For the time, I'm good but at this point will look to target new harnesses. An AC Delco harness connecting the transaxle case and several components runs $230, not including installation. Since that is where the problem seems to be isolated, for the peace of mind and to rule out one less item, probably a good investment. I'll report back if we glean anything further on this.
Thanks again to everyone for the assistance and support.
Thread Starter
Junior Member
Posts like a Ricer Type-R
Joined: Oct 2023
Posts: 21
Likes: 20
If you can help explain, why would I want to isolate the problem on the existing wiring harness versus replacing with new, especially if it is AC Delco. I need to locate someone qualified in my local area but would think the cost of labor for a qualified electrician to perform such testing would exceed what I would pay for a replacement harness and labor to install. I submit I don’t have your knowledge and experience but trying to understand the mindset. Is there a quality concern on replacement parts?
Thank you.
Senior Member
True Car Nut
Joined: Dec 2018
Posts: 3,239
Likes: 1,597
From: Flint, MI USA
Thanks carfixer007. I appreciate the response.
If you can help explain, why would I want to isolate the problem on the existing wiring harness versus replacing with new, especially if it is AC Delco. I need to locate someone qualified in my local area but would think the cost of labor for a qualified electrician to perform such testing would exceed what I would pay for a replacement harness and labor to install. I submit I don’t have your knowledge and experience but trying to understand the mindset. Is there a quality concern on replacement parts?
Thank you.
If you can help explain, why would I want to isolate the problem on the existing wiring harness versus replacing with new, especially if it is AC Delco. I need to locate someone qualified in my local area but would think the cost of labor for a qualified electrician to perform such testing would exceed what I would pay for a replacement harness and labor to install. I submit I don’t have your knowledge and experience but trying to understand the mindset. Is there a quality concern on replacement parts?
Thank you.
A shop that does electrical or advanced repair should be able to quote you.
Thread Starter
Junior Member
Posts like a Ricer Type-R
Joined: Oct 2023
Posts: 21
Likes: 20
A couple of engineers in my company indicated that regardless of whether I repair or replace, they suggest using a combination of heat shrink, heat resistant tape and wire looms to protect the wiring once the problem is isolated. Again, thanks carfixer.
Thread Starter
Junior Member
Posts like a Ricer Type-R
Joined: Oct 2023
Posts: 21
Likes: 20
Well, here'* a new one . . .
Yesterday leaving work, started the car, and the airbag indicator was on. I backed out of my space, put the car in 3rd, car started in 1st gear, advanced to 2nd, stopped at the end of the parking lot and got the delayed bump down to first. Searched up and found someone with a Jeep who had an airbag short cause his tranny to go into limp mode. Reading through, the airbag is connected to the PCM and other electronic control units. More than even am I convinced we have a harness and/or grounding issue. Will keep you posted.
Yesterday leaving work, started the car, and the airbag indicator was on. I backed out of my space, put the car in 3rd, car started in 1st gear, advanced to 2nd, stopped at the end of the parking lot and got the delayed bump down to first. Searched up and found someone with a Jeep who had an airbag short cause his tranny to go into limp mode. Reading through, the airbag is connected to the PCM and other electronic control units. More than even am I convinced we have a harness and/or grounding issue. Will keep you posted.
Thread Starter
Junior Member
Posts like a Ricer Type-R
Joined: Oct 2023
Posts: 21
Likes: 20
I need to get some heat resistant wire loom first but the grounds are included in what we look at next. The smaller looms leading from the air bag sensors on the front of the car appear to be running along with wiring leading into the air filter housing where the PCM is. Not ruling out that there could be corrosion as well in a common area where those wires are.
Thread Starter
Junior Member
Posts like a Ricer Type-R
Joined: Oct 2023
Posts: 21
Likes: 20
So, first off, I hope everyone had an enjoyable holiday season and Happy New Year to all. I still don't appear to have all the right solutions but seem to be getting closer.
The quick updates are we worked through the electrical and all connections to the transaxle, grounds, PCM are in tact. However, the problem has continued intermittently. So, in an attempt to try and capture the issue, I bought a Launch OBD2 Diagnostic scanner. Thus far I've run daily diagnostic reports and captured a few diagnostic records.
The one DTC that comes up every time is P0172 Fuel Trim System Rich. I'm not seeing any other related codes like P0175, or P0442 or P0455 which as I understand are evaporation leaks. Over the last few days, I've made 3 captures of the live data and attempted to draw some correlations. Reviewing the Long Term Fuel Trim - Bank 1, at an idle the value is between -10 and -12. In motion, it ranges usually from -10 and as high as -21. So, I'm pretty confident if nothing else I'm definitely running rich. I need some help to troubleshoot but now wondering if running rich can also mess with the readings from the MAF sensor or vice-versa and contributing to my problem. Recall, I did replace the MAF sensor a few months ago, drove for a few weeks only to have the same problem recur.
The other codes that regularly show up are B3106 Keyless Entry Data Link Parity Error, B0092 Passenger Presence System Passenger Detection Error and a B1004 Radio Error for Keep Alive Memory Reset - none of which I'm sure are contributing to my transmission issue.
Thoughts?
The quick updates are we worked through the electrical and all connections to the transaxle, grounds, PCM are in tact. However, the problem has continued intermittently. So, in an attempt to try and capture the issue, I bought a Launch OBD2 Diagnostic scanner. Thus far I've run daily diagnostic reports and captured a few diagnostic records.
The one DTC that comes up every time is P0172 Fuel Trim System Rich. I'm not seeing any other related codes like P0175, or P0442 or P0455 which as I understand are evaporation leaks. Over the last few days, I've made 3 captures of the live data and attempted to draw some correlations. Reviewing the Long Term Fuel Trim - Bank 1, at an idle the value is between -10 and -12. In motion, it ranges usually from -10 and as high as -21. So, I'm pretty confident if nothing else I'm definitely running rich. I need some help to troubleshoot but now wondering if running rich can also mess with the readings from the MAF sensor or vice-versa and contributing to my problem. Recall, I did replace the MAF sensor a few months ago, drove for a few weeks only to have the same problem recur.
The other codes that regularly show up are B3106 Keyless Entry Data Link Parity Error, B0092 Passenger Presence System Passenger Detection Error and a B1004 Radio Error for Keep Alive Memory Reset - none of which I'm sure are contributing to my transmission issue.
Thoughts?
