Think I may need an ECU!!

Hi all due to my tachometer not working I have carried out the tests from the manual, the yellow / green wire into the back of the clocks is only receiving .88 volts when the engine is running. The manual states it should be getting at least 10.5 volts. So it looks like the ECU is up the spout.

I don't suppose someone would mind checking the voltage on their yellow green wire coming out of the clocks or the end that goes into the light grey connector on the ECU?

I would be so grateful as I know an ECU is not going to be cheap!

 

Troubleshooting ECU issues can be really tricky. Tests in the shop manual are using a PEAK voltmeter and it looks like they are carried out with the connector plugged in. If you are using a regular multimeter without a peak voltage adaptor you may not be able to read the ECU signal. I would think it more likely you have a poor connection, as in a loose connector pin fit...or the tach has simply failed.

 

I'm going with the loose pin idea. As I was juggling lots around when under there.

I just don't know which ones to jiggle and check.

Do you know where I should start looking?

 

Update, when the clocks are plugged in i get 0.91 ignition on engine not running, and 0.88 with engine running.

When the clocks are unplugged i get 12.3 volts ignition on engine not running and 9.3 volts engine running.

 

Love the Tshirt! Brilliant.

Anyone else know anything?

 

The story so far and the checks I have done.

1. Tachometer stopped working whilst balancing the starter valves.
2. Ignition pulse generator working fine.
3. All earths are fine.
4. All fuses are fine.
5. No loose wires.
6. Continuity checked between the ECU and the Tachometer plug into back of clocks, and then into the clocks to the soldered joints, all fine.
7. Voltage checks:

Clocks not plugged in

ECU providing 12.3 volts ignition on engine off
ECU providing 9.3 volts ignition on engine running

Clocks plugged in

ECU providing 0.88 volts ignition on engine not running
ECU providing 0.88 volts ignition on engine running

Lost the plot now and I have run out of ideas. I am thinking again that it looks like the ECU.

Any ideas would be realy helpful at this point. Thank you.

 

Again...are you using a PEAK voltmeter? If not you can't trust your voltage probes...they tell you nothing. RU sure you have proper continuity (less than an ohm) between the ECU and the tach. Even a low resistance could 'muck' things up for you and there is one multi pin connector between the tach and ECU. Did you check for poper earth (we Yanks like to say ground) on the solid green pin in the combination meter coupler itself? Check to make sure a pin isn't backing out of the meter coupler when plugged in. Double check to make sure you have everything plugged back in from your starter valve synch. Double check the ground wire on your fairing subharness. Honda has a 'pin fit' tool to check for loose fitting pins but if you don't have it I suppose that does you no good.

I suppose you could unplug the ECU and comb meter connectors and check for a short between the yellow/green and other wires in the comb meter coupler.

Without the tools (peak voltmeter and pin fit tool) this diagnosis is double tough. Even with the tools you maybe forced to make a guess. I've had to troubleshoot difficult problems like this and I 'feel your pain'.

Hey Ratbiker...I'm curious. In the US we have a recall on your model VFR regarding the electricals...specifically the front fairing subharness and a few other bits and pieces. Do you have the same thing the UK? The real problem area was the solid blue connector (inside the vinyl boot kinda by where your left knee is when you ride). It's a ground junction for the fairing subharness and it wasn't unheard of to see heat damage in that coupler. It might not be a bad idea to check it. I would say the best way is with a test light. Put the earth clip from the light on the positive battery terminal and back probe each pin on the fairing subharness side of the blue connector (it's plugged in for this of course). Look for a pin that gives you a dim bulb on the light.

 

Hi dizzy,

I am using a standard voltmeter at this time. To turn this into the required peak voltage it needs to be multiplied by 1.414 (Google solutions) So I am happy as I can be with the whole matter.

Continuity on the loom is good at 0.2 ohms all the way through which is good news.

I am happy that everything is plugged back in from the SV balance job.

Not sure about a recall for the front harness this is something I am going to have to have a look into, I hope it is that easy!

I will also try the test light tests to see what happens.

It is strange as the bike was getting hot when it was running up in the garage doing the SV balance

Is the ground wire on your fairing sub harness in that light blue connector?

Thanks for your feedback keep it coming!

 

Regarding the peak voltmeter...I don't think it's as simple as a correction chart. Note that in peak voltage testing there is no AC or DC. There are some types of voltage signals a peak meter will read that regular voltmeter can't...such as secondary ignition output voltage. Not being an electrical engineer, I can't explain it in detail. I've been told by people that know more than me that a regular meter isn't a substitute for peak voltage testing for MANY applications and I suspect this may be one of them.

Yes the ground wire for the combination meter (solid green) runs directly through the 18 pin light blue connector I was referring to. You could quickly verify the ground directly at the combination meter connector solid green as well by running a jump wire from it directly to a known good ground, such as the neg battery terminal. Guess it's worth a try.

 

Sorry being a fool now. Can you clarify what I am doing with this negative?

Surely if this wasn't working then the rest of the clocks would not be working either?

 

What you need is a decent digital multimeter, toss anything analog you have. RadioShack here in the US sells decent ones for $60 or so. The wire you're measuring has a digital signal on it (switching between 0VDC and 12VDC at high speed, either at 0VDC or 12VDC, but not at anything in between). If you use a digital multimeter, and put it into "max" mode, it will show the high voltage, if you put it into "min" it will show the low voltage. That you're getting various voltages tells me that you're using an analog DC meter that's trying to show you the average voltage level (which has other uses, but isn't what you want).

It sounds to me like you have a short in the gauge cluster (not a problem with the ECU) as you're seeing 12VDC without it plugged in, and it drops down to ~.8 volts with the clocks connected. That voltage is VERY suspicious as it's the voltage across a diode, which could imply something blew up internally, and you are just dumping current to ground through a diode.

(Digital electronics are something I know quite well: BS Computer Engineering followed by 10 years of working in firmware and electronics)

 

Just the chap...I've been waiting for someone with your experience!

Looking at the pin where the tacho works from it appear a little corroded so I think this could be my problem?

 

You'd think so...but when several items share a ground and it's not a complete open circuit strange things can happen. For example, a few years (before the applicable recall) I came across a V-tec that intermittently ran like crap and/or quit running. The problem WAS the ground in the blue connector I was referring to. When I disconnected it, I found evidence of heat damage on that exact solid green wire. After splicing in a new wire around the connector the problem disappeared. Wouldn't you think in that case the comb meters would have quit working also? But they didn't. BTW, about a year later the recall came out and I was able to replace both the complete harness and fairing subharness for the guy.

Maybe Woody's on to something but I also find it strange that the unplugged VDC you tested at the connector dropped from over 12 to under 10 when (I'm presuming) you started the bike. Other thing...just the connector pin being corroded is potentially enough to create a problem on a sensitive connection like this.

What are you doing with the negative? To answer that question...well I'd do a couple different things. First I'd check the 18 pin blue connector for signs of heat damage on the solid green wire in the corner. Then I'd plug everything except the connector to the comb meter. Find the solid green wire in it. I suppose you could use a meter but I prefer a test light to check grounds. Clip the ground side of the light to the positve terminal on the battery and probe the solid green in the comb meter connector. If it's a good ground your test light bulb should be as bright as if you probed the battery directly. Start the bike and watch the bulb. If it gets dimmer that means something about running your bike is making the comb meter partially lose it's ground, and that's where the voltage drop you're measuring is coming from.

 

As this appears to be a pulse-type signal (ie, it ticks up or down for a moment once per engine rev, or something like that), an analog DC meter will show some steady reading with the engine off, and then some other reading that varies with RPM when running. Either 0 when off and increasing with RPM, or 12 when off and decreasing with RPM. Maybe.. depends on a lot, and since I've never probed these particular lines, I'm just relying on your observations and what I know of how stuff gets built.

So, first rule is the old rule: clean all the contacts and re-assemble with dielectric grease. Make sure nothing's fried in the wiring, and that none of the connections are loose. THEN go in and start looking at the signals if stuff still doesn't work.

 

Update for you all. I have taken the clocks and the ECU to a company to test, they state that the clocks are fine and the tach works on their test rig. So they are thinking ECU.

However the stink of it is that they are not going to go into the ECU due to the 50/50 chance of causing damage to the unit when removing the sealing agent.

Honda want £770 ish inc VAT for a new ECU, then they want money for keys on top of that too!

I got told I could get a 2nd hand unit as long as it came with keys.

I am looking for an ECU!

 

Thanx for the update. UK VFR's must have the security system...HISS is it called? The only US bike it's been used on is the RUNE. When I've suspected an ECU to be the problem it's turned out to be something else. I've been working on Honda's full time for over twenty years (including the FI bikes) and I honestly can't remember seeing a bad one. Based on my experience I think it's more likely you have a 'pin fit' problem, or a poor connection or harness splice. I also understand there's a point in troubleshooting when you really need a 'known good' to find out for sure. Good Luck.

 

I'm going w/ the pin fitment as well.
check all leads before and after the connectors.

 

Right another day spent in the garage achieving nothing.

An idea was put into the pot that it may have been a resistor that had blown in the ECU.

This came about due to the company that tested the clocks stated that they had the rev counter working on a 12v bias with a 4k7 resistor. (Now this means nothing to me.)

The idea was to but a 4k7 resistor in the line form the ECU to the tach to see if that helps at all. Well that did nothing bar lower the already low voltage! (however I did do a lovely soldering job putting the wire back together! )

After clearing all the fault codes on the bike the one that remains is the ECU fault. D'oh.

Me = 0

Viffer = 1

 

well you did get the sync job done so I would say
you = 1
viffer = 1
you're tied now