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I found where the mobile rfi is comming from
- Thread starter groundwire
- Start date
Not sure of the vehicles options or accessories...
But do you have rear window defrost/defog and AM/FM antenna - built into the window, or do you have what some call a "Shark fin" on the roof?
Both can be sources of noise from the re-radiating of the fuel-pumps own return being within the loom itself.
They can capture RF signals (and noise) from local sources and re-broadcast them thru their coaxial routing that also has the DC power going into them to power the amplifier - these things are designed as a broadband block amplifiers similar to satellite dish era, they can even pick up BT and some specific UP-Down load spectrum specific to the vehicles ECM to wirelessly program the ECM thru a dealership or a specialists' tool that can use a handheld scanner to read and upload information into their systems (On star is a good example)
On top of, these types of antennas often have a special cartridge that amplifies the signal to capture "something" to send it back to the radio or in this case, picks up whatever RF is around it, amplifies and sends that back into the loom and front console - amidst the noise you already have from the PCM and ECM units...
Some vehicles like Toyotas' use a RFI Capacitor / decoupler in specific places of the loom for Ground wire returns. The noise suppressor is to reduce the noise from the return, but by their design, the Return needs to have it's ground bond point back towards a location - a relay or ground block - a length of run from the point the device operates, like fuel pumps and in these cases, the profile antennas to reduce the looks of aerial antennas
It's a mess, and due to the nature of the beast, you found the fuel pump, which in most cases now are in plastic housings and to prevent fires, loomed and wires themselves routed to a specific grounding location so they don't produce heat, sparks, or get in the way of the tank.
Unfortunately, the route is long and some cases, very tightly routed along the chassis so your ability to apply ferrite chokes is limited.
They know this so they try other methods of noise suppression - they do these RFI caps they look like bolted harness points, but they are feed-thru caps for this condition - you may have them or you'l see the loom has connectors done up that look like patch cords - that is where these shown above install at, and they bolt to a open "spare nut" bonded to the chassis close by the harness as a place to send noise to ground.
But do you have rear window defrost/defog and AM/FM antenna - built into the window, or do you have what some call a "Shark fin" on the roof?
Both can be sources of noise from the re-radiating of the fuel-pumps own return being within the loom itself.
They can capture RF signals (and noise) from local sources and re-broadcast them thru their coaxial routing that also has the DC power going into them to power the amplifier - these things are designed as a broadband block amplifiers similar to satellite dish era, they can even pick up BT and some specific UP-Down load spectrum specific to the vehicles ECM to wirelessly program the ECM thru a dealership or a specialists' tool that can use a handheld scanner to read and upload information into their systems (On star is a good example)
On top of, these types of antennas often have a special cartridge that amplifies the signal to capture "something" to send it back to the radio or in this case, picks up whatever RF is around it, amplifies and sends that back into the loom and front console - amidst the noise you already have from the PCM and ECM units...
Some vehicles like Toyotas' use a RFI Capacitor / decoupler in specific places of the loom for Ground wire returns. The noise suppressor is to reduce the noise from the return, but by their design, the Return needs to have it's ground bond point back towards a location - a relay or ground block - a length of run from the point the device operates, like fuel pumps and in these cases, the profile antennas to reduce the looks of aerial antennas
Unfortunately, the route is long and some cases, very tightly routed along the chassis so your ability to apply ferrite chokes is limited.
They know this so they try other methods of noise suppression - they do these RFI caps they look like bolted harness points, but they are feed-thru caps for this condition - you may have them or you'l see the loom has connectors done up that look like patch cords - that is where these shown above install at, and they bolt to a open "spare nut" bonded to the chassis close by the harness as a place to send noise to ground.
