I have been chasing a problem in my wife's AP1 '03 S2K for months now. Car spent 3 weeks at the dealership who could not fix it. Many others have reported this problem with varying and similar symptoms. After a lot of sweat and toil, I have isolated the problem and share it with you.

Indications of the problem are:

1. Intermittent speedometer problem: Speedo will indicate accurate speed some of the time, then either generate random speeds or indicate an inaccurate speed, usually much slower than actual. Typical indication is 10-15 mph slower than actual, sometimes 20+. Other cars generate random indications nowhere near actual speed, then return to displaying normal readings for no apparent reason, only to repeat the problem later.

2. Air conditioner problem: Whenever the speedo is indicating wrong, the air conditioning compressor will not engage regardless of switch position. When the speedo is accurate, the A/C will work fine. The air conditioner problem is a common thread to everyone who has had this problem (that I know of).

3. Cruise control problem: Cruise will engage but will not maintain speed; cruise control punches throttle erratically and is basically unusable. Odd thing is that it does not seem to matter whether the speedo indication is accurate or not; the cruise will not work properly either way.

4. One headlight, usually the left one, will occasionally not operate when switched on (how strange is this?).

5. Periodically, all electronic functions will come alive when the key is switched on but the starter will not engage when the start button is pressed. Those who have experienced this symptom have been able to start the car if they jump it from another vehicle and connect the negative cable to the engine block. Connect it to the negative terminal of the battery and you aren't going anywhere.

6. The older your car is, the more likely you are to experience this problem.

7. The more weather your car has been exposed to the more likely you are to experience this problem.

8. Taking the car to the shop to get it fixed results in either (a) the dealership saying the car is normal because they cannot figure it out or cannot duplicate the problem on-scene, or (b) going round and round replacing components and getting nowhere.

9. The Honda procedure for troubleshooting this problem is completely different depending on what particular symptom you take your car to the shop for. Regardless, you are in for a very long and expensive trouble shooting process because Honda hasn't figured this out either. That's where I come in.

My '03 spent 3 weeks at the shop - first diagnosis was a bad fuse box (wrong), second was a bad computer/ECU (also wrong), then numerous relays and switches and black boxes replaced (all wrong), the instrument cluster (wrong), blah, blah, blah.

After the shop gave up I figured it out myself:

On the driver's side of your car, look underneath just aft of the left front tire. There is a grounding wire that comes off of a major portion of the wiring harness that connects to a grounding block built into the transmission casing. The wiring harness grounds to the transmission, then an additional wire grounds this grounding block to the frame. The culprit is the wire that grounds to the frame. The grounding point is completely unprotected from the elements and sits in the path of muck and spray coming off the front tire.

In my case, I completely removed this (filthy) wire and cleaned it to shiny copper and similarly cleaned the lead from the wiring harness, the transmission grounding block, and (especially) the grounding point to the frame.

The frame grounding point is painted and the only conductive bit of metal left to do anything was the threaded portion, which was corroded. Cleaned it all up and now all of the problems above are fixed.

I have read online where 30 or so others have experienced this problem and are living with it with no fix. I hope my pain is your gain! Easy fix and cost is just an hour or two.

I have also read where people have tied this problem to the G101 grounding location on the back of the engine. If you think about it, unless this has rattled loose, it is unlikely to be the problem (and wasn't in my case) because this location is protected from just about everything just because of where it is. The only likely problem at this location is probably a little spilled oil...

P.S. The shop that attempted to fix my car, even after all of the parts we went through, did not charge me anything because they could not fix it. I tip my hat to them for that. I didn't even have to fight them over it.

If this post eases your pain, just ever so slightly, I'm glad I wrote it because that's what it's for!

Cheers!
trent

 

Good find. The "grounding block" you speak of is on the back of the engine, right next to the transmission. It will appear to be on the trans if you are not right up under there and can see the seam.

The ground wire on the back of the cylinder head will cause the exact symptoms if loose. The only way the head ground would be an issue is if the engine or cylinder head was removed.

After cleaning grounds, a coat of any grease will stop further corrosion. Best grease is dielectric silicone.

 

Thanks Billman. I was hoping this would generate some discussion with other terms people might have to make it easier for people to find via google, etc. This was such a PITA for me to finally fix I was hoping that no one would have to go through what I went through!