Help! Bike won’t start..ECM fault?

Hello all,

I’m after some advice for a fault I have on my CBR600RR 2004.

I use the bike as a track bike only and during my last trackday the cooling fan wasn’t coming on. The temperature was showing up to 110 degC on the dash.

When back home I carried out diagnosis procedure stated in my Haynes Manual, and couldn’t get to a root cause. Fan is ok, relay is ok, continuity fine, getting 12v to relay switch side. Just not getting the signal from ECM to come on.

The bike started before doing all this, but now it won’t fire up. I checked everything over and everything is back together correct.

The starter motor is turning on ignition, but won’t fire. I’ve noticed that I don’t get the 2 second whine from the fuel pump priming. Checked relay and is all ok. Checked voltage at fuel pump connector and am getting nothing, so sure fuel pump is fine.

Basically, the cooling fan and fuel pump issues trace back to getting no voltage from the ECM to the relays. So I’m suspecting that the ECM unit is faulty.

I’ve been following the UK/European wiring diagram that is in the Haynes manual.

Is there anything else that I need to check?

If it is the ECM, can I fit a used one off eBay?

Any help would be much appreciated.

Thanks

Martin.

Forgot to say, I also short the ‘fuel cut off’ relay to bypass the lean angle sensor. I am also getting voltage to the relay coil when ignition and kill switch is on, so double sure the lean angle sensor isn’t at fault.

Try a secondary earth from the ECM to the frame. I'm not 100% sure for your bike but cooling fans and the fuel prime are often earth switched via the ECM so if the ECM earth is weak those kind of issues can arise.

Thanks for your advise. How do I go about putting a secondary earth from the ECM?

It is possible that the ecu is faulty after all there was a fault that caused you to perform the fault diagnosis in the first place.

It is a given however that if something is working and you take it apart and reassemble it and then it no longer works then it is faulty reassembly that is the problem.

The bike was starting ok until you disconnected the ecu and then reconnected it and now the bike doesn't start.

If you buy a replacement after wrongly connecting the original ecu then after connecting the replacement it will also be wrongly connected and not work.

Modern ecu units are not user fixable they require a garage to perform the diagnosis. Old bikes like old cars did not run as reliably as modern ecu managed vehicles but they were easily fixable.

Redo the diagnosis that you followed looking for any connection that was made wrongly. check every connector in case one was loosened by the act of being disturbed.

Since you did not take the ecu apart (I hope) the issue is almost certainly an external connection issue.

You may have to put the bike in for diagnosis to fix the original fault.

Not sure you said you checked the fuses?

Obvious I know but alot miss it.