I recently purchased a 2011 Toyota Tacoma and installed a CB radio. Unfortunately, every time I step on the brakes, I get about 2 seconds of an annoying screech throughout the CB. I have gone back to the place where it was installed and he has changed antennas and put in a noise filter, but he is stumped as the noise continues. Any advice would be appreciated.
Where is your CB antenna mounted? If it’s not mounted anywhere near the engine, take a look at how the antenna cable is routed. You might be able to route it away from the source of interference. If the antenna is mounted near the engine, try moving it.
It’s also possible this problem is caused by having the CB radio itself mounted near a source of interference. You might have to relocate it.
I always try to mount my antenna and route my cables as far away from the engine as possible. I also tend to put the radio on top of the dashboard rather than under it.
You could pull the fuses for the brake lights and see if the issue still occurs, just to help narrow down the cause.
I’ve had issues with noise on my CB since I had the engine replaced. Mine is a constant whine in relation to the engine rpm’s. Tried replacing most of the ignition parts with better quality and didn’t help. It had practically no noise for the last 20 years until now.
Weird that yours is during braking, I would expect it’s something with wheel sensors or brake related anyway. Pulling the fuse temporarily is a good idea just to see if the noise stops.
Your best use of time I think is to try to figure out what the source of the electronic interference is. Since it happens when you step on the brakes to stop, but not when you coast to a stop, focus on the electronic events that occur when you step on the brakes.
- brake lights come on
- abs system checks for wheels skidding
- ecm turns off injectors, and monitors when to turn them back on again, making sure engine doesn’t stall
- transmission control circuity is exercised
Of those, my first suspect is the abs. Often there’s a way to disable it by removing a fuse. Suggest to start there. If the problem goes away once the abs is disabled, at least you know where to start to begin solving the problem.
How is your battery power connected to your CB radio? Ham radio operators always connect their ham radios directly to their car batteries to avoid interference problems.
With CBs , noise problems are frequently eliminated with better ground connections on the antenna. When I was trucking, we had to carry our own, radio, speaker and antenna. The antenna was mounted on a vise grip with a mounting tab welded on. Noise problems were almost always solved by taking the antenna and cleaning the tab, bolts, washers and thread connection to the antenna, also the teeth in the vise grio that clamped on the mirror bracket.
We drove a different tractor every night, sometimes changing 2 or 3 times a night.
The antenna is mounted on the roof (magnetic mount) and is routed under the
dash through a grommet in the firewall, under the right passenger side of
the truck, and then back up between the cab and the bed. The radio is
mounted under the dashboard.
The installer double-checked the wiring and could not find any source of
interference. He tried a different antenna with the same results. The radio
was originally wired to the fusebox, but he changed it to directly to the
battery. Same problem.
I will give this a try and let you know. One theory is that that the noise
is somehow connected to the ABS system, but the installer said he had never
seen that problem before.
It has been suggested that the problem may be the ABS system. It certainly
would fit with the 2 or 3 second period of time when I hear the screech (the
ABS system is charging or activating, I¹ve been told).
I will pull the brake fuse and see if it helps.
Thanks for the input.
Thank you. Others have suggested that I check the ABS system. I will have
my mechanic pull the fuse and see if anything changes.
The person who installed the radio initially wired it to the fuse box. He
then wired it directly to the battery and the noise continued.
I have a roof magnetic-mounted antenna. Could these issues (tab,bolts,
washers, etc) be prevalent with this type of antenna?
oldtimer is referring to a clamp on antenna, you wouldn’t have the clamp hardware on the mag mount. I used a mag mount in the past without any grounding issues. I use a fiberglass antenna now bolted to the truck bed.
Another thing you could try is moving the mag mount to the bed and see if the ground is better there. Sometimes the cab is isolated from the truck frame by the rubber cab mounts. You get a better ground when it’s going through the frame. You may just have some weird interference coming from your brake system. If you don’t have damaged wires or sensors, you’ll have to try to shield the source of the noise somehow.
It’s critical the antenna is properly grounded to the chassis, otherwise it will be susceptible to radio freq interference. Ideally the antenna’s ground wire should connect as near to the base of the antenna as is practical. It has to be a really good & tight connection to the car’s chassis ground metal for it to work correctly. A rusty connection or loose connection won’t do. And that same ground should connect to the shield on the coax cable that runs from the antenna to the radio. That’s the configuration that usually works best, but sometimes you have to monkey around with where the grounds connect. It might be better if the antenna ground connects near the radio, or it might be better if the radio ground connects near the antenna. Try it both ways. Interference can get into the radio via the radio’s power supply cable too. Ideally that cable would be a shielded twisted pair construction, routed to avoid running too near to rf generators like the alternator or the various computers in the car, ecm, pcm, abs, etc. Alternators can go bad and cause this too, but since the problem seems to be associated w/braking, unlikely. But you could do a quick test to see if the noise gets worse when you load up the alternator, like by turning on the headlights to bright, or electrical rear window defrosters. If so, that would point to the alternator as a potential culprit. If the antenna-ground is properly grounded to the chassis however, and the shield is grounded, I’m still thinking this has something to do w/the ABS system itself. Perhaps it isn’t grounded to the chassis with a good connection.
If you are using a mag mount the ground connections are between the antenna sheathe and the chassis of the CB, then from the CB to the ground of the car.
I suggest cleaning the antenna plug and where it plugs into the CB with electrical contact cleaner and running a ground wire between the metal of the CB chassis and your negative battery terminal. Assuming you have negative ground.
If the antenna cable is cable tied to the vehicles wiring harness you may get this type of interference. Inspect the routing of the cable, reposition it so it is not near any of the vehicles wiring.
BTW the antenna should be isolated from the vehicles chassis, not ground to it. Do not attempt to ground the antenna. Only the cables shielding should be grounded.
My recommendation is to move the radio from under the dashboard to another location, such as on top of the dashboard or mounted to the ceiling, and route the antenna cable from the radio to the antenna away from potential sources of interference.
The antenna should be grounded at the mount by the shielding. Whether it’s a bolt on or mag mount, the antenna grounds where it’s attached to the metal vehicle surface. You get the best performance mounting the antenna on the roof at the center of the car but that’s not always practical. You should check the antenna performance with an SWR meter. Some radios have an SWR meter built in. If your installer doesn’t have a meter you could look for a CB shop. Some truck stops have a CB shop with a technician.
I have never seen anyone ground a magnetic mount CB antenna, I don’t believe it is necessary. Do you sand the paint on the cars roof down to bare metal?