Hi al,
After 6 months of battling a very peculiar fault and finally solving it, I feel compelled to share my story for any other punters out there.
For reference, I have an Australian 2005 LX470 5 speed auto a750F transmission. Cars is the same, except everything is just mirrored for our USA friends.
Anyway, about 6 months ago I was cruising down the hwy and randomly CELs popped up - no symptoms. A quick scan revealed a P2759 fault code - TC shift lock up solenoid fault. But the car would drive perfect - just the lights! CEL VSC TRC.
After going through the diagnostic process from the workshop, there was nothing obvious (solenoid was only 1ohm out of spec, harness short check was ok). Not wanting to fork out $3k for a new ecu blindly, I tried my hardest to find a direct part replacement part number for the ecu 2nd hand - nothing available and no one was willing to let me try their unit.
Fast forward and talking to those in the know, I was advised that the ECUs are pretty bulletproof and likely just the shift solenoid tripping. Weird I thought, but perhaps as one clue was the code would only come back after clearing when putting the car in reverse. Maybe there's a small impedence causing a fault?
Anyway, I decided to change the solenoid. It did not fix the issue - at least I got my trans serviced at the same time.
Speaking to a few others, my attention was now water ingress causing an intermittent fault. After checking that thoroughly (e.g. pulling off every junction on the front end of the car and inspecting) nothing obvious was found.
Circle back to the ECU. I finally found a same part number ecu for $350 and thought stuff it let's try.
I put the new ecu in and the fault is gone, but now I have a P0778/9 fault. WTF. Car drives worse than before and can't shift into 1st without a huge clunk on the driveline.
Now what? I swapped back ECUs and now I not only have my P2759 fault back, but also the P0778 code. After inspecting shift solenoid B and being confident it's ok - I decided there's definitely something a miss with the ECUs.
Ok fast forward to today and I put the new ecu back in and back to just the P0778 fault. Progress I thought. Then I had some luck. I noticed when plugging the new ecu in there was a SLIGHT kink in the wiring for the shift B solenoid at the ECU end!!
Problem solved, cut and shut that wire and the codes are all gone!!!
Moral of the story: For anyone else that has a P2759 fault, and your solenoids and harness test ok - it's very likely the ECU. If you change the ecu and have another fault, you've probably kinked a wire whilst moving ecus and checking stuff!!!
After 6 months of battling a very peculiar fault and finally solving it, I feel compelled to share my story for any other punters out there.
For reference, I have an Australian 2005 LX470 5 speed auto a750F transmission. Cars is the same, except everything is just mirrored for our USA friends.
Anyway, about 6 months ago I was cruising down the hwy and randomly CELs popped up - no symptoms. A quick scan revealed a P2759 fault code - TC shift lock up solenoid fault. But the car would drive perfect - just the lights! CEL VSC TRC.
After going through the diagnostic process from the workshop, there was nothing obvious (solenoid was only 1ohm out of spec, harness short check was ok). Not wanting to fork out $3k for a new ecu blindly, I tried my hardest to find a direct part replacement part number for the ecu 2nd hand - nothing available and no one was willing to let me try their unit.
Fast forward and talking to those in the know, I was advised that the ECUs are pretty bulletproof and likely just the shift solenoid tripping. Weird I thought, but perhaps as one clue was the code would only come back after clearing when putting the car in reverse. Maybe there's a small impedence causing a fault?
Anyway, I decided to change the solenoid. It did not fix the issue - at least I got my trans serviced at the same time.
Speaking to a few others, my attention was now water ingress causing an intermittent fault. After checking that thoroughly (e.g. pulling off every junction on the front end of the car and inspecting) nothing obvious was found.
Circle back to the ECU. I finally found a same part number ecu for $350 and thought stuff it let's try.
I put the new ecu in and the fault is gone, but now I have a P0778/9 fault. WTF. Car drives worse than before and can't shift into 1st without a huge clunk on the driveline.
Now what? I swapped back ECUs and now I not only have my P2759 fault back, but also the P0778 code. After inspecting shift solenoid B and being confident it's ok - I decided there's definitely something a miss with the ECUs.
Ok fast forward to today and I put the new ecu back in and back to just the P0778 fault. Progress I thought. Then I had some luck. I noticed when plugging the new ecu in there was a SLIGHT kink in the wiring for the shift B solenoid at the ECU end!!
Problem solved, cut and shut that wire and the codes are all gone!!!
Moral of the story: For anyone else that has a P2759 fault, and your solenoids and harness test ok - it's very likely the ECU. If you change the ecu and have another fault, you've probably kinked a wire whilst moving ecus and checking stuff!!!
