Hello



I bought a 2006 Honda Accord in January which came with what I suspect is an ECM/PCM fault – the key has to be turned between stops 1 and 2 many times before the green key light will stop flashing and the VSA light disappears. At this point the engine and coil light come on, go off and everything works fine.



If you don’t do this with the key, the car will crank fine but is immobilised, hence the flashing green key, I am guessing because the ECU does not reset/communicate correctly with the other components. There is a parasitic current draw because if you charge the battery, it will go down to about 11.4v if left, and goes flat quickly if the key is left in.



Another odd quirk is it seems to prefer very cold weather for the ECU to turn on My only guess is a temperature sensor connected to the ECU is PTC type and provides some sort of ground to the ECU when it’s cold outside causing it to reset. Could be talking out of my *** there though.



I’ve read up elsewhere about this fault but only seen one other post anywhere with the same issue, here it is:

https://www.civinfo.com/threads/dies...oblems.101774/



I’ve tried:

- Ensured battery is topped up

- Replacing key battery

- Tried the spare key

- Replacing the receiver ring (changed back because it did not fix the issue)

- Checked fuses

- Pushed the center console and under passenger wiring harnesses around by the ECU whilst shifting between ignition stops 1 and 2

- Read through the factory service manuals and electrical schematics

- Bought and plugged in a MVCI GNA600 HDS clone, but it would not connect because the ECU doesn’t start up.

- Fiddled with the passenger relays out of frustration



Things I have not yet tried:

- Oscilloscope on the CAN lines

- Trying HDS clone with ECU working


An OBDII test shows ABS pump relay open circuit and body ground issues but when you can start it the ABS works if you stamp on the pedal and grounds in the center console are 30ohms to negative battery terminal. That 30ohms is all made up on the wire from the terminal to the body in the engine bay.


Should I take the ECU out and visually inspect the board? The car is on 207k so guessing is about time for it to be serviced.



I have been sitting in the car shifting between ignition stops 1 and 2 all day whilst on charge because the battery was flat, witnessing all sorts of strange behaviour from the computer when drawing lots of current by moving the power seats or windows, namely the display saying “ABS check system” or the stereo display flickering – but no signs of life from the ECU When I got the car, it would only take one or two shifts between 1 and 2 but seems pretty dead now.



I am pulling my hair out – any help is appreciated!
Alex

 

I don't have any brilliant ideas for this, but I think you'll get more people viewing it after I move it to the General Tech. area. The "new member" area is mostly for welcome & introductions.

Hopefully some of our UK members might have ideas. We have never got the diesel engine in USA. But it really seems like there's some flaky connections in the wiring harness, especially ground connections that might be dirty, corroded, loose, or something like that.

 

Do other systems in your car work normally when you put the key to the I and II positions?

Fully charge your battery, connect a volt meter to it. It should read greater than 12.6V fully charged. Turn on the headlights and the battery voltage should slowly drop. If you get a sharp drop, then you may just have a bad battery.

 

Yeah, everything else works no worries except for one thing. The subwoofer (which worked fine in my old car) is quiet without the headlights on - when you switch at least the side lights on, it comes on full power. 12V is present at the sub with headlights on and off.
There are other electrics that don't work at all regardless of key position, these are the heated seats and the DVD player won't read DVDs but doubt these are relevant.

Battery is brand new according to previous owner, but fault persists with different known good battery anyway.
Voltage is 12.6v, this goes down to 12.08v at key pos. II but as mentioned cranks healthily.

Someone told me to replace the fuel filter so bought a new one to fit tomorrow, I know it's not necessary to likely to fix it but I've heard the i-CTDi is really fussy about it.
This would make sense if the ECM/PCM checks fuel before proceeding to ask the immobiliser receiver ring to receive the key code, but I guess that's a question for someone who knows ECU programming inside and out.