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Old 05-16-2019, 10:56 AM
gbalthrop gbalthrop is offline
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Location: Fairfax County, Virginia
Join Date: Mar 2017
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Mein Auto: 2007 328xi E91
Originally Posted by gbalthrop View Post
...So in summary, please don't get "wrapped around the axle" or hung-up on what we DON'T know, but simply [1] change the Voltage Regulator, [2] clear the codes, [3] monitor the voltage at idle after Regulator replacement, and hope that the overvoltage did NOT permanently damage any of the electronics.
Originally Posted by First View Post
...I replaced the voltage regulator along with tensioner pulley and serpentine belt. However, within 30 feet all lights came back on including airbag. Connected the ISTA, and below is what came up in attached images...
My concept WAS (still is ;-) to eliminate a KNOWN fault source, namely OVERVOLTAGE, by (1) replacing the Voltage Regulator; then (2) clear the existing codes; and then (3) MONITOR SYSTEM VOLTAGE (Hidden Menu 9.00, multimeter, or System Voltage Parameter via OBD II Socket).

So NOW you report:
1) You have changed the Voltage Regulator -- GOOD START!!

2) You post ISTA screens showing OLD faults saved at 142584 km & 142589 km, which was the mileage at which the faults you posted BEFORE changing the Regulator were saved. DID YOU CLEAR CODES BEFORE RUNNING THE ENGINE after Regulator change? Do you know HOW to clear codes using ISTA? I use INPA, but have not yet used ISTA, so someone else can hopefully describe how to CLEAR codes using ISTA???

3) You do NOT indicate that you MONITORED the System Voltage (Alternator Output) after engine start, and AFTER changing the Voltage Regulator. Monitoring System Voltage with engine running is the ONLY way I know to determine if the intermittent OVERVOLTAGE issue has been corrected.

So to restate "Next Steps" in simple terms:

1) CLEAR ALL CODES (engine OFF but ignition ON).

2) Connect/Activate System Voltage Monitor of your choice to the vehicle and START engine. Monitor System Voltage as the engine idles. Do that for ~ 5 minutes, noting/ recording MAX voltage observed & MIN voltage observed while engine was running (and alternator was charging). Stop engine.

3) Read Codes with Ignition ON, Engine OFF.

4) Let us know if you have any questions about how to do (1) or (2), and what the results of (2) were (Voltage range), and also (3) codes read AFTER shutting OFF the engine (ignition ON).

The goal is to determine (1) whether replacing the Voltage Regulator has restored proper operation of the Alternator (no more OVERVOLTAGE), AND (2) whether any of the codes that occurred BEFORE recur again.

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