DIY 92-96 Prelude 4WS ECU Repair

**ECU-MAN** · 02-09-2006 11:24 PM

Disclaimer: The following is provided as a GUIDE ONLY, and neither myself nor Ozhonda take any responsibility for the outcomes of someone else doing the following. You follow these steps at your own risk!

this one is for the Prelude owners with 4WS problems. Although your 4WS may not be working, this DIY may or may not be the answer. There is a number of things that can go wrong with the 4WS system.

Best thing to do is start by checking the ECU for fault codes. If you get codes related to the rear motor, or the ECU it self then this DIY might be a good start.

problems this DIY might fix

- 4WS light comes on for no reason while driving after the 4WS was working ok
- 4WS light comes on for no reason while driving on a hot day after the 4WS was working ok
- 4WS light comes on for no reason while driving over bumps
- 4WS light on all the time

problems this DIY will not fix

- faulty steering angle sensors
- faulty rear actuator ( motor )
- miss-aligned sensors
- faulty WSS

if your not sure why your 4WS doesnt work you have nothing to loose by giving it a go, but thier may be other issues, well at least you have eliminated the common 4WS ECU problem.

Aim:

Fix 4WS, save some $$$$

Required:

- 10mm socket and a ratchet to drive it
- Philips head screw driver
- soldering iron
- solder
- electricity ( to power your soldering iron )
- anti static strap
- paper clip or a short connector
- long nose pliers

Steps 1

check the 4WS ECU for fault codes, need to locate the SCS connector and bridge it to put the 4WS ECU into diagnostic mode.

locate the blue SCS connector, drivers side floorwell, behind the center console

( see bellow pics )

unplug the blue connector in the red circle in above pic from the connector holder.

STEP 2

plug in the SCS connector ( or use a paper clip to bridge the connectors )

and get your pen and paper ready

- turn on your Ignition to position II, the 4WS light will come on then go out and start to flash ( if the engine light, ABS and S4 light flash as well ignore them for now and read their codes later )

- count the flashes of the 4WS light, it will have two types of blinks. long ones and shot ones

long ones = tens
short ones = units

example of light flashing

long long long long long long long short short = code 72

you must be patient, after about 2 min if flashing out the codes from the 1st CPU ( main codes ) the 4WS light will blink rapidly for 3 seconds and then the Sub codes will be flashed from the secondry CPU.

record your fault codes, cross refrence your codes from the chart in this great thread by bigteethygrin click here

hopefully you will get codes in the 60's, these codes are common to this fault this DIY will fix.

STEP 3

reset the 4WS ECU and go for a drive to see if the ecu will register the same codes again.

STEP 4

disconnect the car battery
this must be done

remove the 4WS ECU from the car

- remove the back LH seat

- start by removing the lower cusion, the red arrows in the bellow picture shows where you have to lift the cusion and pull in the leaver ( while pushing down on the lower cusion )

- undo the 2 bolts in with your 10mm socket in red circles shown in the pic bellow and lift the seat back rest up and out

STEP 5

the 4WS ECU is exposed

- start by undoing the bolts in the red circles, move bracket out the way
- then undo the bolts in the blue circles

- only loosed the bolt in the green circle, move bracket out the way
- unclip the 3 connectors that plug into the ECU, see blue arrows above

STEP 6

in the bellow picture

- undo and remove the bolts in the red circles
- only loosen the bolts in the green circles

in the above picture

- pry open the black over by pushing the tabs back the green arrows are pointing to .
- undo the bolt the red arrow points to.

- undo the 4 nuts in the green circles in above picture.

remove the 4WS ECU from the car

its a big mumma

STEP 7

place the ECU on your workbench and put on your anti static wrist strap.

- undo the screws in the green circles in above picture

STEP 8

- undo all the screws in the green circles on the logic PCB on the right hand side, take extra care not to damage the flex on the top left corner that joints the two PCB's during this DIY.

- undo all the screws in the green circles on the left side of the ECU, then lift out the matal plate

STEP 9

-undo the screws in the yellow circles, and lift the copper plates out of the way.

- undo the screws in the red circles and lift the relay out the way.

- now undo all the screws in the green circles,

this is what you will have

- this is the PCB we will 1st inspect for dry solder joints..

- lift this PBC out of the chassis and place it on the bench and turn it over.

STEP 10

look at the PCB closely and inspect all the solder joints, use a magnifying glass if you have to.

you need to identify any solder joins that look ghetto like the ones in the picture bellow ( red circles )

some may look ok but they may not be. this is the what a dry solder join looks like. here is a few more pics on different angles of the bad joints

STEP 11

- with your soldering iron reflow the solder on the bad solder joints. make sure the solder penetrates through the PCB but dont over do it and damamge the PCB. also to heat the crap out of it either.

the above picturs are the common joints that suffer from dry solder joints . these are of the relay and relay connector joints, even if they look ok, reflow the solder joint.

I also like to reflow the solder joints of the drivers on the controller PCB

as montioned before check over all the joints on both PCB's and use a magnifying glass if you have to. fix any you find to be sus.

Other comments

**ECU-MAN** · 03-09-2006 01:06 AM

STEP 12

Put the 4WS ECU back together again in revers from disassembly

note; longer screw goes there.

STEP 13

put the 4WS ECU back in the car.

- reconnect the battery

STEP 14

- start the engine and wait till the 4WS light goes out. then turn the wheel full lock to the left, then full lock to the right, then full lock to the left and full lock to the right then center.

this must be done as it sets the 4WS parameters in the 4WS ECU.

test drive the car and make sure everything is ok.

thats it

good luck.

Disclaimer: The following is provided as a GUIDE ONLY, and neither myself nor Ozhonda take any responsibility for the outcomes of someone else doing the following. You follow these steps at your own risk!

**SiR JDM** · 03-09-2006 02:40 PM

Quality work as per usual John. You are a machine, its that simple.

**CUL8R** · 03-09-2006 07:27 PM

john do u mind if i post this up on preludeaustralia? ofcourse giving u all the credit.
writeup would be a fantastic resource

**preludacris** · 03-09-2006 09:32 PM

yeah thats an awesome write up man !

not too many write ups like that for the lude..

no wonder this guy has so many dam rep points!!! haha crazzy

**egSi** · 03-09-2006 10:23 PM

wow.

john > everyone else on OH

**wynode** · 03-09-2006 11:02 PM

+ PQ points for you again John

Nice work and not a DIY you see often.

PS: It's spelt 'light'

**ECU-MAN** · 03-09-2006 11:39 PM

Originally Posted by CUL8R

john do u mind if i post this up on preludeaustralia? ofcourse giving u all the credit.
writeup would be a fantastic resource

yeah no probs, go for it.

Originally Posted by wynode

PS: It's spelt 'light'

it was late when I finished this one

Ill give it the once over now

**Eclipsor** · 03-09-2006 11:47 PM

That's amazing work. Great diy.

Just a question. That's the second diy you've done involving fixing dry solder joints I think. The main relay one too.

Do you know why this seems to be a common problem? Did Honda or whoever manufactured these parts use an inferior mass soldering process?

Or is it simply the result of soldering parts on a car that's constantly vibrating?

**ECU-MAN** · 04-09-2006 12:08 AM

these items that need to have the solder reflowed cary a high current throu them constantly, then there is heat that is generated. its common for this to happen regardless of the quality of the sodlering process over a time period.

Its just nice to know you can fix them like this and not have to replace them.

Honda ECU are built and desined to a high quality and take alot of abuse where other manufature ECU would had failed ( think duracel bunny comercial ). I know alot of cars where the ECU is toast after a jump start gone wrong.

its just one of thoes things