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Car acting up going limp mode when keying CB

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JeepCB

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I don't kniw if this is the right place to ask, i figure maybe ask the radio guys.. maybe someone here know better.

i am having serious problem using cb in my vehicle lately. As soon i key the mic, the check engine and electronic warning lights come up. The idle and rpm jump up very high..

now before you suggest things to do.. pls read the things i did bellow:

this is a jeep jk 2016

-i have changed the cb coax wire 3 times, rerouted inside and outside outside the vehicle in straight line . same with a new ground.
in other words i have the same problem regardless of the coax wire.
-grounded the cb antenna to a dozen of different places on the car. Some ground spots are close to the antenna, other under the vehicle, or near the engine and i even tried directly to the battery.
-this problem happens with 3 different CB !
one of the CB radio is a hand held cobra that use AA battery. Keep in mind That this one is not even draining the car battery.. it is only connected to the car cb antenna. Which antenna is grounded to the vehicle regardless where.
fixed cb are either connected to the car battery or the cigare lighter.
-i have unplug the car battery to reset everything.
i have check many connectors in the engine bay.. nothing seem corroded.. the ground to the ECU( computer module) seem clean..
-This problem happen anywhere, outside of town too..
-i have disconnected every external lights both pos and neg wire from the vehicle.. so the car has nothing aftermarket other than the cb..

things a have not done.. remove the car main head unit stereo.. ( too much work ) remove the spare tire carrier ( too much work). .. remove backup cam which require the removal of the spare carrier.. dismantle the car.. i did took out the ecu from the engine bay to see if i could get the serial and open it.. can't open it. It is sealed..no screw.


As soon i key the mic to talk it basically kill the engine.

i have been on this 8 hours straight and it is driving me nuts

could it be a problem with the car itself? Like a damaged ecu (computer module?)

everything was working before, what is going on? Did a random electric spark blow something but not enough damage to make the car run bad but just enough to prevent the use of a cb?
 

gmclam

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When I first read this, my first thought is how much output power are you using? If you're keeping it legal (5 watts or less), the issue would almost have to be "shielding" on some electronic component in your Jeep. You might try Googling for that.

If you're using more power, the thought that came to mind is "bad ground". Voltage/current that should be directed to the vehicle's electronics is being diverted to an amplifier. If this were my problem, I'd connect an oscilloscope on the power input at the vehicle electronics (Check Engine light usually comes from OBD module but other modules report info) and see what it looks like. Does the voltage drop? Does the ground voltage raise up? Is there a lot of RF on the voltage?

If the voltage is clean the most likely means of interferring is "magnetic coupling" or RF getting into some module it shouldn't be and shielding should resolve that.
 

phask

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I'd check the Jeep's grounds. I have a KJ, but I have heard that some (not sure which) have a grounding issue. Battery to frame or block, block to frame, ECU to where ever.
 

JeepCB

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Updates..

i went to a cb shop (a place that only sell and install cb)

we have been able to duplicate the problem using and hand held 2watts cobra with its own antenna and AA battery.. as soon i key near the throttle pedal, the check engine light and other dash light come on. And idle is reving high.. 3000 rpm.

so it looks like something under the dash near the pedal throttle is grabbing the signal or serve as antenna..

if its the pedal sensor... that is probably a $500 job at the dealer.. but i rather get new pedal sensor than some big truck next to me on the highway killing my jeep because he keyed with a strong signal cb causing me to crash.

my hand helded cb is factory legit..not moded. The base cb unit is 8watts..but it is grounded to the vehicle.

i left the jeep at the dealer for a diagnosis.. but the tech didn't seem to know much after he saw the work order.. he though it was the cb when i left.. i will know later today if he find anything.. if not i will change dealer and pay again for another test.
 

MUTNAV

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If you pull the fuse out that powers the car radio head, and the fuse for the back-up camera, do you get the same results? There may not be a fuse that is specific for those things, but if you can get your car running without them, I would try it and redo your test.

I hope this helps.

Thanks
Joel
 

mmckenna

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As others have suggested:

- Are you running legal power?
- Where is your antenna mounted?
- What type of antenna?
- Have you checked the SWR on the antenna?

You've done some great troubleshooting. Usually when we hear of complaints like this, someone has the coaxial cable bundled up with other vehicle wiring. Keeping a few inches of separation between coax and wiring is necessary.

Grounding everything properly is a good plan. Relying on the negative power lead and/or antenna coax shield for your ground isn't sufficient.

Taking your power feed directly from the battery is required. If you tapped into existing vehicle wiring, you need to fix that.
 

bharvey2

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Given all that you've done, especially using a battery powered CB, antenna placement comes to mind (assuming we're talking legal RF power only). Is it close to the ECU? What kind of antenna and mount are you using? My first instinct is that your SWR is pretty bad.
 

mc48

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Have you connected the ALDL (OBD2) to a scan tool and checked for any codes, or do you have anything else plugged into that port.
Sometimes plugging something into this port can cause a vehicle to go into limp mode. If you have a scan tool let it run when you key up the CB and see what the tool logs when it happens. Disconnecting the battery is not a good move as it resets the ECM and you will not have the status ready monitors if you need an inspection.
Checking the battery is not a bad idea, have someone give it a load test to see how it performs and if it needs replacement.
 

wscranston

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You need to read the code which got set when the check engine light goes on. One of the drivetrain sensors is getting negatively affected when you transmit - figuring out which one will help you zero in on the location. If the engine is speeding up this points to the engine speed sensor, which works using an induced EM field. Could be a leaky coax.
 
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wtp

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ok, now for the serious answer.
after the 2nd CB your work was done.
you now have to shield all the wires in the car.
i remember something about volkswagens doing this a couple of decades ago.
key the mic, kill the car.
 

JeepCB

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Ok problem solved... the dealer removed something i was about to remove myself given more time.. but i didn't remove it because i simply need that device ... and that device has been working flawlessly for a year since i got it..(actually it is still working, just not with CB anymore) it is called a throttle controller....aka pedal commander. It is a useful device for offroading and it goes between the factory throttle sensor male to female connection.. like a T bridge.
that device failed somehow last weekend (i presume) and its funny because it was the first thing i wanted to remove when i was in the mountain.. but it was dark, and cold.. and the kids were hungry... since it was working just fine without the CB i forgot about it...

so now the gas pedal throttle is back to factory... but atleast the cb ( all of them ) are working.. i can key.. still nervously :)

thanx everyone for trying to help... i sure will come back to this forum next time i run into a cb problem.
 

WB9YBM

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I don't kniw if this is the right place to ask, i figure maybe ask the radio guys.. maybe someone here know better.

i am having serious problem using cb in my vehicle lately. As soon i key the mic, the check engine and electronic warning lights come up. The idle and rpm jump up very high..
As soon i key the mic to talk it basically kill the engine.

could it be a problem with the car itself? Like a damaged ecu (computer module?)

everything was working before, what is going on? Did a random electric spark blow something but not enough damage to make the car run bad but just enough to prevent the use of a cb?

It reminds me of what used to happen a few million years ago (or there-abouts) when cars first started using computers to control the engine: the computers would have a fit every time a radio keyed up (especially when the radio was installed in the vehicle). Back then the problem was solved by wrapping the computer & computer cables were wrapped in foil and the foil was then grounded.

Since you mentioned everything worked well before, I'm assuming the problem has been solved in modern cars. The only thing I can think of is that maybe some shielding on the computer or cables (or both) has lost its' grounding...
 

JeepCB

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Yea, im still wondering why it failed in the first place.. i know that i did few electric changes without disconnecting the battery last week.. maybe i did some sparks by accident and fried something.. whatever happened i can not use the cb and the after market throttle controller anymore.. did the throttler controller served as a shield to protect the rest from frying.. i rather lose the throttle controller than an ECU... ecu are slightly more expensive to repair and control alot more stuff.. you can't run a car without an ECU nowadays.. that means i can't even bring the vehicle to the dealer without the ecu.. and you can't order plug and play ecu online , they need to be reprogrammed for your vehicle.

i just hope nothing else is damaged.
 

SteveSimpkin

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Yea, im still wondering why it failed in the first place.. i know that i did few electric changes without disconnecting the battery last week.. maybe i did some sparks by accident and fried something.. whatever happened i can not use the cb and the after market throttle controller anymore.. did the throttler controller served as a shield to protect the rest from frying.. i rather lose the throttle controller than an ECU... ecu are slightly more expensive to repair and control alot more stuff.. you can't run a car without an ECU nowadays.. that means i can't even bring the vehicle to the dealer without the ecu.. and you can't order plug and play ecu online , they need to be reprogrammed for your vehicle.

i just hope nothing else is damaged.
It is also quite possible that the throttle commander was just poorly shielded and allowed RF from the CB to get into the device or into the throttle wiring causing a temporary malfunction. I doubt anything is damaged.
 

a417

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It is also quite possible that the throttle commander was just poorly shielded and allowed RF from the CB to get into the device or into the throttle wiring causing a temporary malfunction. I doubt anything is damaged.
Agreed. The car was probably designed to prevent RFI from causing massive issues, this 'thing' was probably designed to a price point.
 

JeepCB

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Nov 2, 2020
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You could probably wrap several turns of the throttle thing wiring around a 31 or 43 mix snap on ferrite bead as close as possible to the computer that reads the throttle thingee and that will strip off RF currents riding on the wiring.

apparently you need to ground the cb in a way that it doesn't get to the throttle first... but i tried so many grounding points for the antenna already....so im giving up for now.. until i find a solution..
 
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