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Keyless Entry Only Works Inches from Door

15482 Views 9 Replies 4 Participants Last post by  Smurf
Hello All,

RE: 1998 Honda Accord 4 cylinder 2.3L 4dr. Color: smurf-blue!

First of all, I am new to the forum so thanks for the invite...and please let me know if I am incorrectly posting something or not following proper forum etiquette.

I recently had my front and rear engine mounts replaced due to a rough idle and when I got my car back, I noticed my keyless entry fob would only work sporadically---sometimes all morning, sometimes all evening, but not both! After a few days, the key fob stopped working totally. But further experimenting revealed that it worked 100% of the time as long as I was a few inches from either the driver's or front passenger door. When I am this close, everything works: all doors, the trunk release, and arming the alarm.

I have tried logical things first: new fob battery, thoroughly cleaned the fob circuit board, checked all fuses, re-programmed the fob (actually, both of them), and checked the wiring for door lock/window multi-switch. I didn't suspect the driver's door actuator, but I replaced that anyway. (I changed the driver's actuator since it controls all the others, right?) By the way, my car battery is a couple of years old and is pulling 12.59 volts in the morning. I believe this is withing normal range at rest. Anyway, none of this worked.

I believe the keyless entry receiver is not properly accepting the key fob's signal. The car radio signal seems to work properly. I pulled the radio and checked the radio antenna as I believe the keyless entry may be tied into that. It looked properly plugged in. I clicked away and discovered the strongest signal being accepted under the glove box or behind the radio. I pulled out the glove box and passenger lower panel looking for perhaps a loose keyless entry receiver antenna wire or ground connection to no avail. I believe I've found two relays behind the passenger fuse box--I'm not sure. They do click when the fob works. But my next step was to swap them out but I am unfamiliar with the symptoms of a sticky relay. Perhaps this is it?

I have not yet checked the antenna booster coil in the trunk, nor tracked the antenna wire under the center console towards the trunk. It seems like a lot of work for that.

Short of all this, any ideas on what I can do to further diagnose and fix the problem? Any thoughts of diagnosing if both key fobs are just bad? Will a sticky relay cause my problem, too? Is there anything in the engine such as a ground that could have come loose or left unconnected after the front and rear mounts were replaced?

Any help is appreciated!

Thank you,

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The key fob receiver is built into the passenger side multiplexer behind the fuse panel on that side. It has no connection to the radio antenna. You seem to have covered the usual suspects, new fob battery, cleaning connections, etc. Since you had recent work on the motor mounts it would be logical to look for wiring problems in the engine compartment. Otherwise you may want to pull and inspect all the panel fuses for corrosion. Last resort might be to replace the passenger side multiplexer.
Thanks for the advice!

Problem solved. It took me awhile. I pretty much eliminated everything. Car battery and voltage were OK. Key fobs cleaned. New fob battery. Reprogrammed. Checked fuses. Checked voltage and amperage at the fuse circuit going into the passenger multiplex when clicking the fob. Checked the door multiplex and side multiplex wiring. Eliminated the relays as faulty. Checked positive connections and engine grounds. All this led me to isolate the problem: it was the passenger side multiplex that appeared to be faulty.

The psm (passenger side multiplex) is housed in a blue plastic box and measures about 4X5". It plugs into a series of 24 pins that come from the fuse box.

I took out the glove box and kick panel and was able to remove the psm/blue box without any problem. I opened the box and checked the circuit board but saw nothing obvious. There were a couple of joints that did not look right so I re-soldered them but that still was not the problem. The bigger capacitors did not appear to be leaking (though I did not test them.)

I took the psm in and out several times and still no luck. I removed the blue box and just put in the bare circuit board. It still didn't work right.

Then, I started pressing on the back of the exposed circuit board in different areas while pressing the key fob. Would you believe there was one spot on the the board where the receiver signal was strong again. Though I couldn't really test it by walking away-I was tied to pressing down at this one spot. So I duct-taped that pressure point in position and went to the curb. Click. Doors unlock. Click. Doors lock!!!!! Click. Trunk popped open!!

Finally, I put the glove box back and applied permanent pressure by wedging some hardwoods between the glove box and the (duct-taped) psm circuit board. This took time to get the right pieces of wood. The area of the pressure spot is about an inch square. I put everything else back, slammed the door, went curbside and clicked away....


There is one component on the circuit board that I believe may be the antenna??? It was labeled L1. "L" usually stands for an inductor. I had cleaned it out with rubbing alcohol but to no avail. Funny, there was a small hole in the blue box that is only aligned to this one component, leading me to believe this one item is significant. Why the access hole? There was a square hole inside L1 that maybe a tech can adjust either the signal or tune the frequency???? Anyway, the pressure point I speak of is right at that one component.

The test will be to drive it around on bumpy roads. If the wedges get loose, I'll have to get more creative in permanently applying the pressure on that one spot. I know I can think of something. But the best part is that I know it will work!!!!!!

I know this an odd way of resolving this but I love working on problems of this sort. Especially when they work out! I have some pictures but I don't know how to post them just yet.
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Good diagnostic, that sounds like a broken circuit board trace to me, or a internal component failure which goes away when pressure is applied.

The inductor is a tunning coil for frequency adjustment at the factory through the square access hole you observed, I would suggest re-solder all the solder joints in the area of the circuit board, you may have a cold solder joint, just don't put too much heat in the joints to avoid damaging any components.

As for broken trace, that would be hard to track down, especially if it is a multi-layer circuit board which means you may never actually find a broken trace.

Try the re-soldering trick to see if it makes a difference.

The only other suggestion I have is to spray electronic contact cleaner into the inductor/coil housing in case contamination over the years has caused the value of the coil to vary slightly.
That explains L1 and the hole! Thanks so much. I tried cleaning it with rubbing alcohol and a q-tip but I couldn't get it in the hole for a good cleansing. If it should act up again, I will try cleaning L1 with an electronic contact/switch spray. Radio Shack for that??

I tried looking for cold solder joints but didn't see any. The pcb has the tiniest of components and some of the board has a layer of brushed (?) coating of some sort...hard to get at. And you are right, there are multi-layers within the board. I did solder a couple of joints but it didn't help. Actually, the capacitors were my first worry as I suspected leaks, but saw no obvious signs so I left them alone.

The pressure I applied seemed to be right at L1, so maybe I will try to re-solder it's (4) solder joints next time.

OK, I must confess, I should just get a new passenger side multiplex and be done with it, but this is way too much fun to diagnose and rig-fix, especially on my fixed budget.

...I am going to try to attach some pictures...

~~Retirement is great. Everyone should try it once in a lifetime. DO NOT WAIT.
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Attached are five photos.


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Hello again. The jam fit would work, but I had to keep adjusting it every 4-5 days as the wood slipped a bit at the plastic glove-box. I suppose I could have used Velcro or something more creative to make it more secure. But, I resolved the matter permanently.

I re-soldered the solder joints for component "L1" even though the joints looked OK. It's been over 12 days now and it's working like a charm!!!! I have no idea why this one component's joint would begin to fail, or perhaps the weaker connection was just enough to throw off the signal/frequency for the receiver? Regardless, it is resolved and I have been clicking away much to the neighbors' annoyance.
i had a similar problem with my 91 accord. it was the main relay had 1 bad solder point. wouldn't start. fixed that joint, and poof she fired right up. i had to use my jewelers visor with a 10x lense to see it. good job finding/fixing the problem.
Thanks everyone for all the input! This forum is great. Shaggy: I re-soldered the L1 joints without using a magnifier during pre-inspection. I think with it I could have possibly seen the bad joint to begin with (though the PC board did have multiple layers.) I am going to see about getting the jewelers visor for future use. Thanks for the suggestion!

BTW, and slightly off topic, was it difficult to remove your main relay and take it apart to get to the circuit board, and what were to symptoms (sporadic starts)? My one and only non-Honda car stalls when re-starting the engine when warm and I'm wondering if that could be a faulty main relay/solder joint you speak of.
Key Fob Only Works Inches from Window: Great Update!

I have one more very intriguing final chapter to my key fob problem. My key fob is totally fixed and then some! I am updating this in hopes others can benefit...

Just a recap...key fob would work but only when the near the front windows. I found that pressing at a certain location on the passenger side multiplex unit worked well, but the wood jams I used would loosen over a few days. What really worked was re-soldering the joints of the L1 inductor on the PSM. I got back the 30-35' range again and it's been working great over two months now.

Well, I don't know what got into me. Maybe it was an overnight visit by Martians. Then I realized we don't allow Martians here in California. Anyway, I started thinking how I can improve my key fob range. In my garage I found three metal bookends that probably held down Encyclopedia Britannica from my youth. The bookends have an arch, a tongue, and the "other guy". I bent the "other guy" so it's on the same plane as the arch. I then inserted the tongue in between the glovebox and the blue box housing of the PSM; the tongue free-floated between these. I took a second bookend, flattened it out, and gorilla duct-taped it together with the first. I then taped this entire apparatus to the front side. My theory is to better capture and bounce the RF signal from the key fob transmitter; the tongue would capture the RF signals better and the outer metal of the apparatus would help.

Next, I took another bookend and totally flattened it out. I removed the passenger side fuse box panel and duct-taped that over the fuses. No worries...replacing fuses is as easy as moving the the bookend to the side or removing it when the time comes. Again, the theory is to better capture the RF signal. I am trying to better capture the RF signals from both sides of the PSM box.

I put back the knee panel and fuse panel. I parked in a totally open parking lot with no obstructions and walked away from the front of the car clicking away. I can see by my blinking lights and horn when the key fob would work. 30' away, click--everything works. 50' away, click. 80' away, click--still working! Wow. This is exciting. 120' away, click!!! 150' away, click!!! It still clicked at 200' away!!!! That is TWO HUNDRED FEET AWAY!

The bottom line is that my homemade deflectors from the metal bookends totally worked and took me from a 35' range to 200' with very little effort and no $$.

I hope my pictures come through. My apparatus took about 20 mins to install. And it's been almost six weeks and it's still working without fail. Disclaimer: when parked near cars or objects, the signal strength is reduced due to the interference but is still multiple times better since I installed my apparatus. If you try this, find yourself an empty open lot to experiment.

Sorry folks, I am not that technically savy so I can't really explain why I am now getting a 200' range. No complaints here. Maybe some of the real radio guys can chime in.


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