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Discussion Starter · #1 ·
I have a 2004 M3 and my reverse sensors do not work. They used to work, but one day they stopped. I don’t hear a buzzing sound when I put my ear to the sensor when the car is in reverse and the fuse appears to be good. I got the car manual swapped and my ECU was recoded, so i’m not sure where to start or what to look for. Any info helps. Thanks.
 

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86 Posts
Discussion Starter · #3 ·
The 4 sensors located on my rear bumper, other forums say I should hear a light buzzing whining sound from these sensors when the car is in R.

Unsure if the manual coding affected these sensors. It happened around the same time, but I can’t recall it happening on the same day.
 

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E46 330ci Sport Convertible 2002
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202 Posts
The below opinions are based on my experience from my E39, which should be similar, as I have not had any problems with my E46.

If a sensor fails then when you engage reverse you get a continuous tone.

Sensor failure is most common followed by wiring/connectors.

If not that then possibly the module.

Hooking up the car to a laptop with diagnostic is the best way to trouble shoot. You can see a the faults on the system and run tests.

Replacement sensors from BMW are very expensive. On ebay they are cheap but some are good and some not so. I know which ones to buy on UK ebay but that won't be any use to you so others may be able to recommend.
 

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330ci Coupe 6MT
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1,953 Posts
First thing I'd do is scan the PDC (Park Distance Control) module for any error codes.

However I'm just wondering if when they recoded your DME (the engine ECU) for manual they copied the entire VO (vehicle order) from another car that was already manual, which would populate all your modules with the default values from that car, rather than recode just your DME, which would have left everything else alone. I believe few US cars had PDC, so if they did that your car would no longer know it had PDC installed.
 

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43 Posts
The below opinions are based on my experience from my E39, which should be similar, as I have not had any problems with my E46.

If a sensor fails then when you engage reverse you get a continuous tone.

Sensor failure is most common followed by wiring/connectors.

If not that then possibly the module.

Hooking up the car to a laptop with diagnostic is the best way to trouble shoot. You can see a the faults on the system and run tests.

Replacement sensors from BMW are very expensive. On ebay they are cheap but some are good and some not so. I know which ones to buy on UK ebay but that won't be any use to you so others may be able to recommend.
Yo can you give me the link ? people say ebay sensors only work on the 2 middle i brought one from there and my pdc still not working
 

· Sofa-king-what
'00 323Cic manual
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2,364 Posts
there is a difference in activation depending on the gearboxes, or by pin 15 (auto/smg) or by reverse switch (manual).

before doing anything better to do a diagnosys via INPA to check the effective functionality of each sensor
the boot tone is a good marker (long one = error)
keep in mind that some aftermarket (most of them) they do clicks, they get read by inpa, showing distances, but are not well digested by the system that fails to acivate (long beep)

if i'm not wrong VO doesn't need to be updated in case of retrofit (not 100% sure)
 
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