Where are groundings on XX located?

[hotdogpork]

Hi folks, need some help identifying where the grounds on the bike are (I assume they're attached to the frame?) Mine is an 02 model if that matters, thanks.

[79cbxmike]

Remove the seat and you will see a ground connection on the frame cross-member left side, a lug screwed down with two wires on it.

There is a battery to engine ground connection accessible mid-engine just below all those hoses and sensor connections. The heavy wire leads back to the battery. See page 1-27 in the Honda shop manual.

[79cbxmike]

By the Way: The service manual is pinned and available in the useful threads section of the Public Discussion Forums guide.

[TuffguyF4i]

Remove the seat and you will see a ground connection on the frame cross-member left side, a lug screwed down with two wires on it.

There is a battery to engine ground connection accessible mid-engine just below all those hoses and sensor connections. The heavy wire leads back to the battery. See page 1-27 in the Honda shop manual.

Yup...2-3 wires coming out of it. 2 hole loop connectors and a big honking lug.

All the wires are green.

[79cbxmike]

Keep in mind that while there are three major ground points (battery to ground, starter ground, and the lug on the cross-member) there are many splices within the wiring loom as it branches off to serve devices (sensors, lights, switches, etc.)

Exactly why is this important to you (and the bike of course)? Just curious.

[hotdogpork]

thanks for the tips. I've been getting the dreaded 25 blink problem and it isn't the knock sensor. Mine is an 02 model. Have done the loom fix (although it might not be necessary on an '02). Problem went away for a month by itself (without me resetting the code) and now it's back. Just thought I'd check the grounds.

[79cbxmike]

You can verify integrity of ground wires on a sensor or device by running a separate ground wire from the green terminal (on a sensor or device) to the engine, chassis or battery negative terminal.

I would suggest connecting a wire to the chassis ground on the frame cross-member to an alligator clip you have soldered on the other end.

I believe the knock sensor is grounded through it’s own case threads and has only one wire hooked to it which runs to the ECM. Maybe just loosening and reseating the knock sensor will insure a good contact. Keeping it simple I would check the wire to the computer as describe in the manual on page 5-54 (could be wrong here maybe someone else on the forum knows this for sure).

In any case: How do you know the knock sensor is good? Just asking.

[hotdogpork]

You can verify integrity of ground wires on a sensor or device by running a separate ground wire from the green terminal (on a sensor or device) to the engine, chassis or battery negative terminal.

I would suggest connecting a wire to the chassis ground on the frame cross-member to an alligator clip you have soldered on the other end.

I believe the knock sensor is grounded through it’s own case threads and has only one wire hooked to it which runs to the ECM. Maybe just loosening and reseating the knock sensor will insure a good contact. Keeping it simple I would check the wire to the computer as describe in the manual on page 5-54 (could be wrong here maybe someone else on the forum knows this for sure).

In any case: How do you know the knock sensor is good? Just asking.

Hi Mike,

Thanks very much for the tips. These are the things I've done to troubleshoot the problem:

1) Changed a brand new knock sensor from dealer, reset fault code. (no help)

2) Checked continuity between knock sensor plug and pin on harness which goes into ECM. (check)

3) Checked connection and fit of plug on knock sensor (check)

The only option left for me is a bad ECM. Do these things go bad often? Almost everyone I've spoken to who've owned a blackbird in my country has had this problem if their bikes had any amount of age. Read from another post the bird ECM goes bad after 4 years?

Another thing, my mechanic also wired up a lot of spare grounds to frame for me, however we didn't check the engine ground. Is there anyway for me to do a quick and dirty check that the engine ground is ok without removing a lot of stuff?

I can't read electrical diagrams, but will any other problem in any other part of the harness cause this fault to trigger, or is this fault solely isolated to the knock sensor circuitry (i.e. the ECM must be the only culprit left)?

[cbrxxquad]

Did you do the loom fix or clean the plug? If you did the removal of the plug, you might have a cold solder connection.

[hotdogpork]

Did you do the loom fix or clean the plug? If you did the removal of the plug, you might have a cold solder connection.

yes i did the loom fix (soldered them all together), but what plug are you referring to?

[79cbxmike]

Today I am going to follow the procedure on Pg. 5-54 of the shop manual on my own Bird (which runs perfectly ) and consult with the local Honda dealer, there may be a service bulletin on this test.

I believe the manual has some errors in the proceedure.

A dirty or bad connection could cause your code.

Hang in there a while, don't go spending a fortune on an ECU yet.

[cbrxxquad]

Did you do the loom fix or clean the plug? If you did the removal of the plug, you might have a cold solder connection.

yes i did the loom fix (soldered them all together), but what plug are you referring to?

The plug you removed, when you soldered the wires together. NO pictures here anymore, but does this sound like what you did.

See the deal with the knock sensor is that it has to have a reading within a range, to adjust the timing. If continuity is compromised so is the range.

I have never had a problem, but bad fuel might cause it to knock too.

I would see what the resistance is in the wire from Sensor and to the EFM.

[hotdogpork]

Today I am going to follow the procedure on Pg. 5-54 of the shop manual on my own Bird (which runs perfectly ) and consult with the local Honda dealer, there may be a service bulletin on this test.

I believe the manual has some errors in the proceedure.

A dirty or bad connection could cause your code.

Hang in there a while, don't go spending a fortune on an ECU yet.

Thank you! Please let me know, would appreciate that very much!

Did you do the loom fix or clean the plug? If you did the removal of the plug, you might have a cold solder connection.

yes i did the loom fix (soldered them all together), but what plug are you referring to?

The plug you removed, when you soldered the wires together. NO pictures here anymore, but does this sound like what you did.

See the deal with the knock sensor is that it has to have a reading within a range, to adjust the timing. If continuity is compromised so is the range.

I have never had a problem, but bad fuel might cause it to knock too.

I would see what the resistance is in the wire from Sensor and to the EFM.

Yes, but mine is a 2002 so my plug was yellow. Frankly I don't think the plug was the problem for post 2002 birds because the contacts were all very clean inside, but I could be wrong.

I also don't think the light is showing because the engine is knocking; i think the light shows because the feedback loop is somehow not working. Either the ECM is not recieving any signals from the knock sensor when it is supposed to or perhaps like you say the signal is unexpected. I will try to check the resistance this weekend or when I can find time off work. My gut feel is that this is not a mechanical problem at all (i.e. engine knocking, bad fuel) but rather an electrical fault. I've heard that some ECMs in other vehicles perform a diagnostic test of the knock circuitry by purposely advancing timing till the engine knocks slightly and then listen for a signal from the knock sensor. If it gets none it flags a fault.

What does everyone else think?

[cbrxxquad]

I have had this discussion about what the sensor does and you can do a search. It might help. And reading the manual. Lets just say it generates a signal in the sensor. The ecm has to see the signal within a range or it codes.

Yeah the 2002 does not need the repair. You know those crimp connectors that you lock on a wire to tap into it, the plug is like that inside but a bar for the wire. used to connect a bunch of the same wires together with a buss. But if the signal is degenerated across the buss enough to fail the range, it codes. I don't know if the knock sensor goes through there, doubt it does, but the connection at the ecm should be good for it read. Clean and tight.

Look at the diagram it will confirm. It is just one wire.

[hotdogpork]

I have had this discussion about what the sensor does and you can do a search. It might help. And reading the manual. Lets just say it generates a signal in the sensor. The ecm has to see the signal within a range or it codes.

Yeah the 2002 does not need the repair. You know those crimp connectors that you lock on a wire to tap into it, the plug is like that inside but a bar for the wire. used to connect a bunch of the same wires together with a buss. But if the signal is degenerated across the buss enough to fail the range, it codes. I don't know if the knock sensor goes through there, doubt it does, but the connection at the ecm should be good for it read. Clean and tight.

Look at the diagram it will confirm. It is just one wire.

ok thanks. so I guess no point for me to go looking for bad grounds then? I'm clueless about electical diagrams so apologies for the inane questions.

[cbrxxquad]

I have had this discussion about what the sensor does and you can do a search. It might help. And reading the manual. Lets just say it generates a signal in the sensor. The ecm has to see the signal within a range or it codes.

Yeah the 2002 does not need the repair. You know those crimp connectors that you lock on a wire to tap into it, the plug is like that inside but a bar for the wire. used to connect a bunch of the same wires together with a buss. But if the signal is degenerated across the buss enough to fail the range, it codes. I don't know if the knock sensor goes through there, doubt it does, but the connection at the ecm should be good for it read. Clean and tight.

Look at the diagram it will confirm. It is just one wire.

ok thanks. so I guess no point for me to go looking for bad grounds then? I'm clueless about electical diagrams so apologies for the inane questions.

Not inane at all. I understand the fear of wiring diagrams. I am a drafstman, in an earlier life. But it is just lines conecting boxes. The trick is find the box, and follow the line to the other box, find out what it is. Done.

But the written section on the knock sensor is pretty informative, in a lot of ways. I would say educational, which is unusual. To a point.

[hotdogpork]

Today I am going to follow the procedure on Pg. 5-54 of the shop manual on my own Bird (which runs perfectly ) and consult with the local Honda dealer, there may be a service bulletin on this test.

I believe the manual has some errors in the proceedure.

A dirty or bad connection could cause your code.

Hang in there a while, don't go spending a fortune on an ECU yet.

Hey Mike,

Just wondering if there's been any update from your conversation with the Honda dealer? Was there a service bulletin issued on this test? Thanks!

[79cbxmike]

I did talk to the Honda dealer (a rare find, competent, trustworthy) and they have never dealt with a knock sensor problem and were not even aware of this device in the Bird. That said; they do have an excellent library and file system for updates and service bulletins, there are no service bulletins on the Bird knock sensor or testing.

We did agree that the procedure is faulted; as soon as the weather moderates I will roll my Bird out of the garage and test it. Also plan to look at the waveforms at the sensor and ECM.

Rarely manuals do contain mistakes; the original CBX shop manual had one installing the camshafts incorrectly causing the cam timing chain to snap.

Knock sensors work on the same principle as some microphones, some vinyl record pickups and many other devices that have been around for decades (senses vibrations and puts out a voltage) no new technology or rocket science here. They have a constant low level output signal which increases when the engine knocks.

The questions are –

1. how does the ECM generate a fault Code? Does it display a fault if the normal signal is missing OR display a fault with excessive knocking – OR maybe either/both?

2. What does the ECM do to ignition timing in face of no sensor signal?

We are thinking your problem is a bad/intermittent connection between the sensor and the ECM.

[cbrxxquad]

What I got is a minimal required voltage, or a code is created, excess volt retards timing till required voltage is met.

Thought testing parameters were present, but have not looked, for.

[hotdogpork]

I did talk to the Honda dealer (a rare find, competent, trustworthy) and they have never dealt with a knock sensor problem and were not even aware of this device in the Bird. That said; they do have an excellent library and file system for updates and service bulletins, there are no service bulletins on the Bird knock sensor or testing.

We did agree that the procedure is faulted; as soon as the weather moderates I will roll my Bird out of the garage and test it. Also plan to look at the waveforms at the sensor and ECM.

Rarely manuals do contain mistakes; the original CBX shop manual had one installing the camshafts incorrectly causing the cam timing chain to snap.

Knock sensors work on the same principle as some microphones, some vinyl record pickups and many other devices that have been around for decades (senses vibrations and puts out a voltage) no new technology or rocket science here. They have a constant low level output signal which increases when the engine knocks.

The questions are –

1. how does the ECM generate a fault Code? Does it display a fault if the normal signal is missing OR display a fault with excessive knocking – OR maybe either/both?

2. What does the ECM do to ignition timing in face of no sensor signal?

We are thinking your problem is a bad/intermittent connection between the sensor and the ECM.

Thanks very much Mike. Please let me know the results if you get around to testing it.