Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance
Posted: Tue Apr 29, 2025 4:48 am
This might be a good place to crosspost a link for an LDU issue that might be becoming more prevalent nowadays, with the aging LDU population: the LDU Control PCB has a resistor network consisting of R105/R106, 40.2Ω SMD resistors, that link chassis ground and encoder ("speed sensor") grounds. One resistor becomes intermittent, making the paralleled resistance ~40Ω instead of ~20Ω.
On the RAV4 EV, this manifests in Tesla codes:
@ogmm in Guatemala chased this symptom publicly @ myrav4ev.com and tracked it down to those resistors Nov2024 (link to his "aha!" post). Meanwhile, Aug2024 I had purchased another RAV4 EV that had that symptom. Last week, I was able to reproduce the test conditions (test resistance between ENCG and INV GND, found ~20Ω, pressed on PCB and obtained ~40Ω), and I replaced those two resistors to stabilize the reading. Yesterday, I was able to test drive ~2 miles and had no reoccurrence (other issue prevented me testing further), so I'm calling it "probably fixed". My few posts after the above link document what I found on mine, and how I repaired it.
As this LDU Control PCB is exactly the same part (and Tesla part No.: 013416-00-x) as the one installed in the Model S, I expect more reports of this issue to occur. Once the PCB is removed from the LDU -- and it pretty much has to be removed, as SMD rework on a partially inverted PCB is nigh impossible -- the conformal coating can be heated and scratched off around the resistors, and due to the relatively large format of these resistors -- 2512 -- they can be replaced easily. Probably even without a hot air station, though I didn't have to try that.
New and used boards are plentiful right now via eBay, but knowing what I do and seeing two failures of one of these resistors, I think I'd consider replacing them any time I have a used PCB in my hands, going forward. But that's just because it happened to me plus one other that I know of.
I know that pics are only thumbnails over there unless you register, but photo handling is so much easier there than here that I can't repost them all here, but here's a few.
While I tested at connector D14, it's probably a lot easier to test between chassis ground (LDU case) and ENCG at the encoder. You can't press on the PCB, but if you can get the LDU into a fault state and quickly measure, if it's not 20Ω, you know what the issue is.
On the RAV4 EV, this manifests in Tesla codes:
- DI_f020 speed sensor problem detected
- DI_w020 Speed sensor problem detected
- DI_f108 Drive not possible because of other system problem
@ogmm in Guatemala chased this symptom publicly @ myrav4ev.com and tracked it down to those resistors Nov2024 (link to his "aha!" post). Meanwhile, Aug2024 I had purchased another RAV4 EV that had that symptom. Last week, I was able to reproduce the test conditions (test resistance between ENCG and INV GND, found ~20Ω, pressed on PCB and obtained ~40Ω), and I replaced those two resistors to stabilize the reading. Yesterday, I was able to test drive ~2 miles and had no reoccurrence (other issue prevented me testing further), so I'm calling it "probably fixed". My few posts after the above link document what I found on mine, and how I repaired it.
As this LDU Control PCB is exactly the same part (and Tesla part No.: 013416-00-x) as the one installed in the Model S, I expect more reports of this issue to occur. Once the PCB is removed from the LDU -- and it pretty much has to be removed, as SMD rework on a partially inverted PCB is nigh impossible -- the conformal coating can be heated and scratched off around the resistors, and due to the relatively large format of these resistors -- 2512 -- they can be replaced easily. Probably even without a hot air station, though I didn't have to try that.
New and used boards are plentiful right now via eBay, but knowing what I do and seeing two failures of one of these resistors, I think I'd consider replacing them any time I have a used PCB in my hands, going forward. But that's just because it happened to me plus one other that I know of.
I know that pics are only thumbnails over there unless you register, but photo handling is so much easier there than here that I can't repost them all here, but here's a few.
- LDU Control PCB 013416-00
- LDU Inverter Connector D14
- Discolored 40.2Ω SMD resistor
While I tested at connector D14, it's probably a lot easier to test between chassis ground (LDU case) and ENCG at the encoder. You can't press on the PCB, but if you can get the LDU into a fault state and quickly measure, if it's not 20Ω, you know what the issue is.