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Discussion Starter · #1 · (Edited)
I want to reset the ECU on my 2005 V70 2.5t. I just bought it and put in 92 octane gas so I figure the ECU has no reason to spontaneously adjust timing from the retarded settings it would have set for the dealer's 87 octane. It makes sense to reset the ECU so it "assumes" the proper fuel is being used.

Option 1 is to disconnect the battery. As I understand the procedure is to turn off the radio, AC, etc and then disconnect the negative terminal for 15 minutes. Edit: Then put the ignition into II and reconnect

Option 2 is to pull fuses. But I can't find any info on which fuses. There are several threads where someone asks, and then says "I figured out which 4 fuses" without posting which fuses they pulled. Or even someone replying "Pull 2 fuses" without saying which! So which fuses? And is there any reason not to use this method vs disconnecting the battery?
 

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In the engine bay fuse panel there are 2 fuses (forgot which ones) labeled ECU on the legend or something like that.

Pull the fuses, turn key to pos III (of course engine won't start), remove key, replace fuses, start the engine a drive according to the IPD TCV relearn procedure.

Originally Posted by IPD Instructions

After the installation of the ipd HD TCV drive the vehicle for 5 minutes without developing any boost
pressure to allow the engine to warm up. In a safe and appropriate place, accelerate the vehicle
to approx half of its maximum boost level and hold there for 5-7 seconds, then decelerate to below
30mph. Proper accelerator modulation will be necessary to control the boost level. Repeat this 4 times.
Turn the engine off and wait for 12 minutes. For optimum results the above procedure should be

performed twice.
 

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Discussion Starter · #5 ·
In the engine bay fuse panel there are 2 fuses (forgot which ones) labeled ECU on the legend or something like that.

Pull the fuses, turn key to pos III (of course engine won't start), remove key, replace fuses, start the engine a drive according to the IPD TCV relearn procedure.
Wow, how the heck do you know when it's making half boost?
 

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Wow, how the heck do you know when it's making half boost?
Well if you don't have a boost gauge, just go for a couple runs starting at 25%, then 50%, then 75%, then 100% throttle and it should be fine, just don't demand full throttle off the line after a reset or it will most likely put you in limp mode. You're just trying to get the ECU to learn and adapt to optimal settings. It continuously learns through regular driving, but sometimes a hard reset will correct some issues, and a hard rest is always a good idea when servicing the engine. I do one every oil change :).
 

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Discussion Starter · #7 ·
Well if you don't have a boost gauge, just go for a couple runs starting at 25%, then 50%, then 75%, then 100% throttle and it should be fine, just don't demand full throttle off the line after a reset or it will most likely put you in limp mode. You're just trying to get the ECU to learn and adapt to optimal settings. It continuously learns through regular driving, but sometimes a hard reset will correct some issues, and a hard rest is always a good idea when servicing the engine. I do one every oil change :).
Easier said than done on Oahu-- On most roads if I do 50% throttle for more than a few seconds I'm way past the speed limit :p

BTW the manual lists an ECU fuse on the left side of the dash
 

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Easier said than done on Oahu-- On most roads if I do 50% throttle for more than a few seconds I'm way past the speed limit :p

BTW the manual lists an ECU fuse on the left side of the dash
Ok, I'm out front at my car right now. I pop the hood, remove the fuse panel cover, note that fuse #6(ECM,MAF,INJECTORS) and #23 (ENGINE CONTROL MODULE), place the cover back on the fuse panel, close the hood, lock the doors, open my browser to this thread, and post my findings. :D

You can pull the additional fuse in the passenger compartment if you wish (don't know if it will affect anything), but I've never had an issue resetting the ECU the way I described.
 

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Or you could just go for a drive with the new gas. I think you're over complicating this.
 

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How would the ECU know to adjust timing for higher octane?
The O2 sensors mostly.

You probably wouldn't speed up the learning time by resetting the ECU either. It will still need to re-learn once it is reset.
 

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The O2 sensors mostly.

You probably wouldn't speed up the learning time by resetting the ECU either. It will still need to re-learn once it is reset.
Actually the knock sensor.

My limited understanding. The ECU will push the the timing to the knock threshold until it senses knock then it will back off timing slightly. On a reset ECU it will push it constantly until the ECU has learned the knock threshold of the current fuel in the current operating conditions (ambient temperature and pressure, engine condition). In normal driving the ECU will continue to push the knock threshold regularly to optimize power/fuel economy while maintaining safety for changing conditions. High octane fuel has a higher knock threshold so the ECU is able to advance timing more than with lower octane fuel (more timing = more power)

The ECU will eventually learn to adapt to it in time, but I'd suggest a reset to take advantage of it as soon as possible.
 

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Discussion Starter · #14 ·
Actually the knock sensor.

My limited understanding. The ECU will push the the timing to the knock threshold until it senses knock then it will back off timing slightly. On a reset ECU it will push it constantly until the ECU has learned the knock threshold of the current fuel in the current operating conditions (ambient temperature and pressure, engine condition). In normal driving the ECU will continue to push the knock threshold regularly to optimize power/fuel economy while maintaining safety for changing conditions. High octane fuel has a higher knock threshold so the ECU is able to advance timing more than with lower octane fuel (more timing = more power)

The ECU will eventually learn to adapt to it in time, but I'd suggest a reset to take advantage of it as soon as possible.
I'm going to try it as soon as I get a chance, because the gas mileage is so horrible... Something has to be off somewhere. I'm up to 18mpg average according to the computer :p There is no way a FWD wagon should be getting worse gas mileage than the typical 4000lb 4WD SUV
 

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I replaced the filter

Should I get Bosch Platinum plugs? Bosch 4028 FR7DP (Platinum)
No. Get OE plugs only. You'll regret buying anything else (although I had cheap Champion coppers in mine for a few thousand and it wasn't that adverse). I've heard of many buying expensive plugs only to rip them out later.
 

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Discussion Starter · #19 ·
No. Get OE plugs only. You'll regret buying anything else (although I had cheap Champion coppers in mine for a few thousand and it wasn't that adverse). I've heard of many buying expensive plugs only to rip them out later.
Ordered the OEMs from FCPEuro... Now I'm nostalgic about the 1996 328IS I had that I ordered a huge number of parts for from FCP
 

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Discussion Starter · #20 ·
On my last tank I got 16.6mpg!! That officially makes it the least efficient vehicle I have owned-- Worse mixed gas mileage than a 1999 V8 4WD Grand Cherokee, a 1999 4WD I6 Cherokee, and a 2006 V8 Mustang.
 
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