2006 Toyota Sienna Can PCM cause mechanical transmission fa

REASTWOOD

MEMBER
2006 TOYOTA SIENNA
6 CYL
2WD
AUTOMATIC
130,000 MILES

I have a 2006 Toyota Sienna which we started noticing some irregular shifting and loss of transmission performance. We took it to AAMCO to check out before we took it on vacation and they indicated that the torque converter was bad and caused transmission damage. They indicated that the transmission had to be replaced along with the torque converter. Since they already had the transmission open, I knew I was screwed. I reluctantly agreed to have the transmission replaced. I paid $3600. The transmission failed 3 weeks later so I took it back. AAMCO rebuilt the transmission and it failed again (something about the high gears fusing together in a drum). They replaced the whole drum with the high gears in it and it failed again. AAMCO said it must be the PCM so they repaired the transmission again and they towed it to a local Toyata delership which confirmed the PCM was bad. They replaced the PCM and when we drove it off the lot, the transmission was failing again (eratic shifting, no acceleration. Etc). We took it back and the dealership said it was mechanical in the transmission but they stood by the statement that the PCM had been bad and it needed replaced. AAMCO said that the Toyota delership drove the car around with the bad PCM which caused the transmission to fail again so they have no responsibility. My question is: Can a PCM cause this kind of mechnanical transmission failure?

1 Reply

KHLOW2008

MECHANIC
41,814 POSTS

Hi reastwood,

Thank you for the donation.

Sorry to hear of your plight. Whatever it is, it is not your fault and the problem should be resolved between the dealer and AAMCO. Get both sides to sit down and talk it over and let them decide who should be responsible. Let them know you would be making a report with the local authorities if they are not able to come up with a solution for you.

PCM can cause the trans to fail as whenever the transmission goes into limp mode, it would not up or down shift and this would cause overheating and the clutches to be fused.

I believe both parties should be responsible for the problem and AAMCO cannot shirk their responsibility.

The transmission should not fail even if the PCM is bad as technicians should be able to understand the problem and refrain from driving any further.

The other likely cause is that the rebuild had not been done correctly and even if the PCM was good, the trans would still fail.