Whining/Buzzing ETM... what can cause this?

Post by **bmdubya1198** » 02 Jul 2019, 09:18

My ETM has been causing problems since I got this car, and I've finally put together exactly (what I think, at least) is happening. I have had two codes (ECM-6B00 and ECM-6300, one is for ETS light signal too low and the other is CEL signal too low) and they seem to be linked to the CEL and ETS lights "flickering" if they're illuminated.
The codes will always come back immediately after clearing them once I start the car as instructed in VIDA.

I have noticed that when this happens, the ETM is making a strange and relatively loud buzzing/whining. When I first start the car and the warning lights are tested, the lights will only do the flickering thing if the ETM is buzzing, but if it's not, they are steady and act normally. It's also only once I start the car that this happens, it has never happened with the engine not running.
They'll also flicker if one or both are illuminated for any other reason (other unrelated issues that have come up). But again, only about 80% of the time, other times they'll be solid, as they should (when the ETM isn't buzzing).

I have replaced the ETM 3 times, so that's not the problem. I just checked and cleaned the ground for the ETM the other day, but it was already pretty clean. I have already checked for excessive resistance in the wiring between the ECM and cluster (the wires that the codes above point to) and they are good. I checked the CAN bus wiring between the ETM and ECM and the resistance is fine there was well, no changes if I move the harness around.
I've also checked all the other grounds throughout the car, everything is tight and clean.

Does anyone have any idea what could be wrong? I have a strong feeling that fixing this will fix these codes so I can finally take comfort in knowing there aren't any strange electrical issues.

Here's a video. This was taken before I pinpointed the ETM as the culprit, so I'm moving my phone around the whole engine bay. You can still hear it pretty clearly, though.

Post by **abscate** » 02 Jul 2019, 09:41

When you did the manual swap, did you bridge the B1 and B13 back from the ECM to the CDM?

Check those for MY 2000, as they might be different but I recall there are some CANBUS connections to 4/22 that might not like being left open, too.

Sorry, thats about all I got on this.

Post by **bmdubya1198** » 02 Jul 2019, 18:24

abscate wrote: ↑02 Jul 2019, 09:41 When you did the manual swap, did you bridge the B1 and B13 back from the ECM to the CDM?

Check those for MY 2000, as they might be different but I recall there are some CANBUS connections to 4/22 that might not like being left open, too.

Sorry, thats about all I got on this.

I did, and I checked that connection again as well. I had originally used vampire connectors, but I went back in there and soldered the connections to make sure they were solid.
That should all be good unless the wiring changed in 2000... according to the 2000 AW55 TCM diagram, the green on the ECM side is the CAN bus high side, and the white is the low side, and the wires going to the CDM are the opposite (green is low and white is high). However, I don't know if that's correct. The diagram for ME7 within this same document shows white as high and green as low on both the ECM and CDM (well, from the ECM to TCM then the TCM to CDM, respectively). From the research I did at the time, green goes to green and white goes to white.

Post by **bmdubya1198** » 03 Jul 2019, 16:23

Can anyone tell me how many ohms to ground you're seeing at the green/white wire at the ETM connector (engine harness side)? It sits around 12 ohms, but if I disconnect the PTC it goes up to 1400 ohms. I traced it back to the PTC by pulling fuse 11B/5 (emissions fuse, 20 amp in main fuse box).

I had previously run the car with it disconnected, but I don't remember that making any difference. This is also the second PTC I've had in this car, so I don't think it's the problem. Probably more dead ends. Ugh... this has gone on for too long.

Post by **bmdubya1198** » 03 Jul 2019, 16:42

Also, if I disconnect this connector (24/43) the green/white wire at the ETM goes high resistance (1400-1500 ohms). Why is this happening?

Edit- duh... the connector also contains a green/orange wire for the PTC/TCV/other stuff. When it's connected, it links the PTC (source of the ~12 ohms to ground I'm seeing) to fuse 11B/5, which then links to the rest of the fuses in that panel, which pushes that resistance onto, eventually, the green/white wire at the ETM.

Post by **bmdubya1198** » 08 Aug 2019, 16:34

I can pretty much confirm that the codes (ECM-6300 and -6B00) are NOT related to this issue.

After replacing the B+ fuse box cable, that seems to have fixed those codes. However, a new code has appeared that may be related to the ETM whine... ECM-912A (Communication with ECM- Signal Missing). It's an ETM-related code.

I've checked the wiring already between the ECM and ETM, everything is perfectly in tact. All I can think is that the battery cable between the starter and battery needs to be replaced, there is a little corrosion on the wires right near the lug, which could be a problem. Voltage at idle is around 13.8V.