Jump to content
SheldW3

CPU Questions

Recommended Posts

SheldW3

Howdy Guys & Galls,

 

So my 700x has been playing up the last month or so. The fuel pump was activating while at the top of snowdonia car park and so i had to get transported back home (some 200miles away). Once home i started trying to fix the problem myself, from a killswitch diode/fuse, battery, spark plugs. I managed to replace the fuel pump (the small motor that sits inside, next to the fuel level meter) thinking that was the issue. It was not. So after long hours researching i thought it could be the CPU (computer). So after taking it to the local Honda garage the run a diagnostic they have narrowed it down to a possible two problems. Either it is the mirco chil in the keys that the CPU is not reconising (causing the fuel pump not to prime and thus not start) or it could be a damaged CPU, in which case i would need to either buy a new one (which id rather not becuase i would have to sell my kidney to pay for it) or what was recommended is to find a scrap nc700 and transport that CPU and keys to my motorcycle. 

 

Now that your up to speed with the issues, has anyone else has similar issues that doesnt lead to a very expensive part? Or any mechanical advise to try save £££? Would be much appreciated!

 

SheldonW

Share this post


Link to post
Andy m

Get them to try and set-up a new key for the current ECU. It's highly unlikely to be the ECU unless there has been welding or jump starting. Electronics are very very tough, they only get blamed because the grease monkeys think they are full of voodoo demons. 

 

Andy

  • Like 1
  • Haha 2

Share this post


Link to post
SteveThackery

In general it's far better to diagnose the fault properly rather than swapping stuff until it works.  I mention it only to avoid you spending even more money unnecessarily. :)

 

I'm with Andy on this - the chances of the ECU showing such a fault are extremely small.  Getting a new key is the next step.

 

By the way, I don't trust any mechanics when it comes to diagnosing electrical problems.  There must be some competent ones, but in my 45 years of motorcycling I've genuinely never met one.

  • Like 2
  • Haha 1

Share this post


Link to post
Tex

 

2 hours ago, SheldW3 said:

So after taking it to the local Honda garage the run a diagnostic they have narrowed it down to a possible two problems. Either it is the mirco chil in the keys that the CPU is not reconising (causing the fuel pump not to prime and thus not start) or it could be a damaged CPU, in which case i would need to either buy a new one (which id rather not becuase i would have to sell my kidney to pay for it) or what was recommended is to find a scrap nc700 and transport that CPU and keys to my motorcycle. 

 

Could just as easily be a poor connection in the fuel pump circuit, or at the relay, or at the fuse. Steve is right ‘shotgun diagnostics’ (firing new parts at a problem hoping one will hit the spot) is a huge, frustrating (and expensive) pain in the rump. Are there no decent automotive electrical specialists in your town? Most have one, somewhere.

 

  • Like 2

Share this post


Link to post
ste7ios

Diagnose as described in the service manual. There are diagnostic codes for most of the possible faults.

 

Have you any idea how expensive is just to replace the PCM or the rest of the components? 

 

More than $650 for the PCM, the lock set $160, the fuel pump more than $400...

 

Most probably it’s a bad connection somewhere... 

 

  • Like 1

Share this post


Link to post
embee

Not sure what you mean by "the fuel pump was activating", however ……………...

 

Right. I've had issues in this parish.

 

Check the connector for the kill switch/starter on the right side switch cluster. The connector is about a foot or so away down the wiring harness (mine is an Integra so not exactly the same). Mine had a couple of tarnished pins in this connector. The electrical circuitry is that power runs up to the kill switch, then through the switch, and then off down to the fuel pump relay. It also supplies the starter switch. Mine lost power to the switch block, it behaved as though the kill switch was off.

5cdca581d7c9f_NC700starterswitch.jpg.0d0ce65af829617372188e70d674e760.jpg

 

The other thing to check is the fuel pump relay. On mine it sits at the front of the fairing right hand side, I would guess on the X it might be in a similar place. There are two relays which are identical, one does the fuel pump and the other does the fan. On my bike the fan relay failed. To confirm this I swapped the fuel pump and fan relays and the fuel pump failed to run. I fitted new relays to both and everything worked fine, so definitely the relay. I picked up a couple of brand new genuine relays off the auction site from a place which prepared bikes for racing, so electrical stuff became spare. I carry the old original relay as a spare for when I'm touring, t's a tiny item but a failed fuel pump relay would spoil the day (as an emergency measure just fit the fan relay to the fuel pump and make sure you don't get caught in traffic jams).

 

  • Like 2
  • Thanks 4

Share this post


Link to post
SheldW3
13 hours ago, ste7ios said:

Diagnose as described in the service manual. There are diagnostic codes for most of the possible faults.

 

Have you any idea how expensive is just to replace the PCM or the rest of the components? 

 

More than $650 for the PCM, the lock set $160, the fuel pump more than $400...

 

Most probably it’s a bad connection somewhere... 

 

Yeah its not cheap! Hopefully it is!

Share this post


Link to post
SheldW3
8 hours ago, embee said:

Not sure what you mean by "the fuel pump was activating", however ……………...

 

Right. I've had issues in this parish.

 

Check the connector for the kill switch/starter on the right side switch cluster. The connector is about a foot or so away down the wiring harness (mine is an Integra so not exactly the same). Mine had a couple of tarnished pins in this connector. The electrical circuitry is that power runs up to the kill switch, then through the switch, and then off down to the fuel pump relay. It also supplies the starter switch. Mine lost power to the switch block, it behaved as though the kill switch was off.

5cdca581d7c9f_NC700starterswitch.jpg.0d0ce65af829617372188e70d674e760.jpg

 

The other thing to check is the fuel pump relay. On mine it sits at the front of the fairing right hand side, I would guess on the X it might be in a similar place. There are two relays which are identical, one does the fuel pump and the other does the fan. On my bike the fan relay failed. To confirm this I swapped the fuel pump and fan relays and the fuel pump failed to run. I fitted new relays to both and everything worked fine, so definitely the relay. I picked up a couple of brand new genuine relays off the auction site from a place which prepared bikes for racing, so electrical stuff became spare. I carry the old original relay as a spare for when I'm touring, t's a tiny item but a failed fuel pump relay would spoil the day (as an emergency measure just fit the fan relay to the fuel pump and make sure you don't get caught in traffic jams).

 

Wow, thanks for the help dude! The garage said they were going to check all of the keys and link them up with the ECU (incase they have been damged or not linked up before). I think (hope) this will solve the problem because what i didnt mention before was that my main key broke a few month ago and so i started using one of the spare keys. I didnt think this would cause an issue (being chipped too) the problem did start around this time! 

 

Im waiting to hear back from the mechanics soon (next few hours) so when i do i will keep you guys posted. 

 

Thank you so much for all the help guys!!

  • Like 1

Share this post


Link to post
SheldW3
14 hours ago, SteveThackery said:

In general it's far better to diagnose the fault properly rather than swapping stuff until it works.  I mention it only to avoid you spending even more money unnecessarily. :)

 

I'm with Andy on this - the chances of the ECU showing such a fault are extremely small.  Getting a new key is the next step.

 

By the way, I don't trust any mechanics when it comes to diagnosing electrical problems.  There must be some competent ones, but in my 45 years of motorcycling I've genuinely never met one.

Good point! I think my mechanical curiousity gets the better of me (and my wallet) sometimes :lol: Ill make sure to diagnose the issue before stripping her down 

  • Like 1

Share this post


Link to post
SheldW3

UPDATE for those who are interested! Just got off the phone with the Honda service and MOT garage and they "dont know what the issue is". They have checked the fuel pump + connections, H.I.S.S, spark plugs and all is working fine.

 

Will update tomorrow when they have check over her again 

  • Like 2

Share this post


Link to post
Andy m

Working fine as in starts and rides? 

 

That's classic loose/cruddy connection. Blast silicon spray in every electrical bit, give it a thorough wash then start riding in ever increasing circles. You'll only find it for certain when it's an active fault. Computer diagnostics in particular are very binary. 

 

I tell every trainee to start by looking round the vehicle. The pipe hanging off saves getting the laptop out of the car. I still get the calls where they've changed the ECU three times and the fault remains. At this point I can only tell them what the fault is not. The younger they are the sooner laptop comes out. 

 

Andy

  • Like 4

Share this post


Link to post
embee

What exactly is or isn't it doing? I wasn't quite sure from the original post exactly what the issue is.

Share this post


Link to post
Mr Toad
On 5/15/2019 at 18:22, Andy m said:

Get them to try and set-up a new key for the current ECU. It's highly unlikely to be the ECU unless there has been welding or jump starting. Electronics are very very tough, they only get blamed because the grease monkeys think they are full of voodoo demons. 

 

Andy

 

But we all know that once you let the magic smoke out it's game over.

  • Haha 1

Share this post


Link to post
embee

As a follow on from my earlier post, if the problem is that the HISS isn't displaying and the fuel pump doesn't run, then that's exactly what you get when the power isn't getting through the kill switch. Easy thing to check whether power is getting there and whether it's getting out again.

You can check this on a "good" bike by turning ignition on with the kill switch off and seeing exactly what happens. When I had this issue we checked another Honda to be sure what should display, and mine was doing exactly what that did regardless of whether the kill switch was on/off. The switch turned out to be fine, but power wasn't getting to it.

  • Thanks 3

Share this post


Link to post

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×