I've got this 2000 540i 6MT with 90k miles, exhibiting a no-start condition with the following symptoms:

1. Temp gauge immediately pegs red when key is turned to position 2
2. Throttle motor is silent
3. Starter motor engages and cranks
4. DME has no communication with PASoft scanner

Previously, the above would occur alongside an ENGINE FAILSAFE PROG warning in the cluster, and the DME would come alive and start the engine with no performance degradation, if the EF1-5 fuse pack was removed and reinstalled. (But only if all 5 fuses were removed and replaced; none of the other DME-related fuses had any effect, and reseating any other combination of fuses had no effect) I verified that all related fuses and relays are functioning as expected, and that there are no wiring issues or water intrusion issues. Suspecting a DME fault, I sent the unit (along with my EWS and key) to a company specializing in repairs.

When they returned it, the car started and ran normally for a couple of weeks, but then after about 200 miles of mixed driving, the engine stalled and would not start again. The previous workaround has no effect. Additionally, the ENGINE FAILSAFE PROG warning does not illuminate. Prior to sending the unit for repairs, once the engine started, it would stay running with no issues until turned off with the key; this is the first time it's stalled while driving.

When I asked the ECU repair company what was done to repair my unit, they said they didn't discover any physical fault in the DME, but that the data was corrupt. (And so they charged me $300 to "repair" my DME by re-flashing the unit while it was already hooked up to the test scanner) Having pulled the unit apart myself since then, I can't see any evidence of physical damage either. No signs of cold solder joints either.

Before I burn another $50 on shipping it back to the company, who will no doubt simply repeat the same re-flash trick and call it repaired under warranty, what could be causing the DME to go corrupt like this? I'd expect to see some physical signs of damage if something inside the DME were busted up enough to cause EEPROM contents to be corrupted, but I also don't know of anything the rest of the car could do to trick the EEPROM into corrupting itself.

The ECU repair company suggested a bad alternator could cause this, but not only does that not make sense (at least in absence of chips releasing the schmoo) but the alternator is fine and produces a solid 13.8v at operating temperature, with a cold-start peak of 14.3v. For that matter, the battery is less than a year old, and the car is connected to an appropriate battery tender when it's parked for more than a couple days.

Has anyone seen this before? I'm at a loss.