Resetting the ECU by disconnecting the battery

[mickburkesnr]

I'm not sure whether I read this on this forum or on a different one, but the subject was in regards to MPG of a car and someone suggested disconnecting the Battery to reset the ECU. It isn't the first time I heard this, about 8 years ago a guy I was working with said he had to do this every 6 months on his diesel Mondeo to improve performance.

I have just done my first full week in my 1998 Toyota Corolla 1.3 and it's done 310 miles on one full tank (so I'm roughly on 31mpg). The car was only ever doing trips to the local dump, about 3 miles round trip and now it's doing 30 miles round trip. So I filled it up with BP petrol (last week was Esso/Tesco stuff) and used the Redex treatment in both tanks. I decided to give this a go, so I disconnected the Battery and left it over night as I wasn't going to drive it anywhere last night. Honestly I wasn't expecting anything to happen other than have an oil spanner after it.

This morning I went to the shop in it, MY WORD! Who has swapped my car? The throttle response is much better, sounds to be revving more freely, and I'm getting to 30mph a lot quicker.

I'm sold I think on this technique, but I'd like to know whether anyone else has seen a noticeable difference in their cars doing this?

[FROSTYBALLS]

Resetting the ECU by disconnbecting the Battery has been mentioned n threads on the Auris club.

[Anthony Poli]

Resetting the ECU causes poor fuel economy, while the system sets up during the first 500 miles or so. The car seems to have a ore response to the accelerator during the set up, but the mpg is much lower. 

Maybe a better idea would be is to use a obd wifi dongle and something like dash command or torque, to record the sensors. More chance of spotting causes of poor mpg, like O2 or air flow sensors. It is possible to catch problems that are missed when having a routine service done.

[mickburkesnr]

I've ordered a OBD2 bluetooth reader for the car which I was going to use for an onboard computer so I can look at the data in real time and after journeys etc. In my head I thought I'd do it because looking at the millage the car has done over the last 4/5 years and that the woman I bought it off said it didn't do long journeys it would reset the ECU and would set itself up to my driving style.

I'll know in a week or two's time whether it's improved the MPG or not anyway, but I'm enjoying the more responsive engine now!

[Anthony Poli]

Sadly the obd reader will just clear fault codes, it won't reset the ecu.

It will help in diagnosing some problems.

I had an intermittent O2 sensor, that the dealer missed, because most of the time it was working properly. 

When comparing the sensor to an identical car, i could see it wasn't responding as quickly and hence giving me a worse fuel economy. So i was prepared for the repair cost.

I have reset the ECU a couple of times, usually when i have been replacing the Battery or getting to the headlight. This hasn't helped do anything to improve the mpg. Good operation of sensors and good maintenance will do more for your mpg.

Even a knackered Battery can cause poor mpg.

How old is your corolla?

 

 

 

 

[FROSTYBALLS]

From the first post - 1998.

[mickburkesnr]

Yeah I know the OBD won't reset the ECU, I didn't buy it for that purpose. I'm hooking it up to a computer to record information the OBD gives out (hopefully) such as rev's, speed etc. If it works (which it should do) I'm going to post a how to about it because so far it's cost about £20 in parts and can be used on any sort of car.

And yeah, it's 1998. 22 years old and driving lovely!

[Anthony Poli]

We had a 2000 and a 2001 corolla in the family. Bought the OBD reader because of the MIL light, just to save the cost of the dealer investigating the cause.

Also proved useful to see how hybrid system worked