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Post Info TOPIC: HOW-TO power the ECU during programming OFF-BIKE


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Posts: 964
HOW-TO power the ECU during programming OFF-BIKE


To program an ECU that has been removed from the bike in addition to connecting to a BDM port adapter you will need to provide power and programming voltage. The CPU inside the ECU is powered by a 5V power supply built into the ECU and operates off the ECU power input which can range anywhere from 7 ~ 18 Volts DC.

Normal power input is all that is required to establish a BDM connection and READ the flash memory. In order to ERASE or WRITE to the flash memory also requires a 12VDC Programming Voltage (Vpp) be applied to the CPU. On the face of it this would not seem hard to find 12V to input into the ECU.

The problem is Vpp needs to be exactly 12V (11.6 ~ 12.4). Less than 11.6 and the CPU will not program the flash, too high and you risk damaging your CPU and making your ECU unusable. In the automotive world '12V' could mean anything from 11V to 15V. A full charged 12V lead acid battery for instance actually provides 13.8 Volts. Using something like your '12V' Battery Charger or a spare battery on your bench is not going to work.

Also going into the house and finding some old wall adapter from your answering machine or going to radio shack and buying a 12V power supply or wall adapter is no guareentee of getting a device that actually provides exactly 12V.

Another consideration is that Vpp should never be applied before the normal ECU power or removed before ECU power or damage to the ECU could result.


The easiest way to prevent this is to power both the ECU power and Vpp off the same power supply.

You need a power supply that will provide between 11.6 and 12.4 volts at a 150mA.

Measuring an 'unloaded' power supply is not an accurate indication of operating voltage.

Many small power supplies like wall adapters may be marked 12V but actually are very poorly regulated and may output more or less than their rated voltage depending on load (amps) applied.

How to test your power supply

Since the main ECU main power is very forgiving you can use it for a load to test your power supply. DO NOT CONNECT VPP DURING THIS TEST.

  1. Carefully connect +12V of your candidate power supply to pin 17 of the ECU and ground or negative lead to pin 18 (see diagram below)
  2. Turn on your power supply and measure the voltage across pin 17 and 18. If it falls within 11.8 ~ 12.2 VDC it is safe to also use for a programming supply.
  3. Turn off power supply and remove connections from ECU.
Once a proper supply has been found connect the ECU as follows

Always turn off / unplug the power supply when connecting and disconnecting the power wires to the ECU


-- Edited by RidgeRacer at 18:22, 2007-10-29

-- Edited by RidgeRacer at 18:26, 2007-10-29



Status: Offline
Posts: 964
HOW-TO physically connecto to the ECU

OK you have your power supply but how do you actually connect it to those little pins on the ECU connector?

You could use some very small alligator clips but whatever method you use you need to be extremely careful you dont short the neighboring pins to the power pins or you may ruin the ECU.

Short of finding an extra wire harness on eBay what I have found works best are some crimp on pins that come with a 25 Position Female D-Sub Connector (Radio Shack #276-1430)

Crimp or solder a wire to the end and then wrap with tape or use some heat shrink tubing to insulate it and you have the perfect little ECU individual pin connector.

A small 22 ga wire will work fine. In programming mode the ECU only uses 150mA. It not like your firing any injectors or anything.

-- Edited by RidgeRacer at 19:06, 2007-10-29

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