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Parking Sensor Diagnostic Help
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Discosimon888
 


Member Since: 12 Jul 2024
Location: Luton
Posts: 7

United Kingdom 2007 Discovery 3 TDV6 SE Auto Cairns BlueDiscovery 3
Parking Sensor Diagnostic Help

I’ve got a recent problem with my parking sensors, and could do with a pointer as to where to look next.
As soon as I select reverse, I get a solid tone from what I assume is the front sounder. The light on the parking sensor switch is on - no flashing and no error message on the screen - if I press the button they turn off as normal. I get no sound from the rear sounder whilst the front is constantly on.
I only have an Autel scanner, there are no recorded faults but it tells me the front right inner sensor is reading 0mm when nothing is in front of it. No fault codes stored for the parking sensors. The only oddity I noted is that on the Autel it says front sounder and parking aid front sensor inactive???

I have tried:
- a new sensor - still exactly the same 0mm reading
- cleaned all connections to each front parking sensor and the front sensor connector behind the head light.
- continuity tested the loom for the sensor in question - all three wires fine back to the connector under the headlight (and no shorts between them either).
- with the connector unplugged, I get a reading of around 25M Ohm between the brown and black pins with all sensors connected.

Any tips where should I look next?

Thank you!  
Post #237312212th Jul 2024 9:23 pm
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Discosimon888
 


Member Since: 12 Jul 2024
Location: Luton
Posts: 7

United Kingdom 2007 Discovery 3 TDV6 SE Auto Cairns BlueDiscovery 3

Picture of diagnostics added.

Or maybe not - it won’t let me upload!  
Post #237312312th Jul 2024 9:24 pm
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Pete K
 


Member Since: 15 Jan 2016
Location: GL
Posts: 10669

England 2005 Discovery 3 TDV6 HSE Auto Rimini RedDiscovery 3

Replacement sensor could be faulty.
Try a known good front one in the troublesome position.
See if fault moves with sensor.


Otherwise it could be ecu ?

Check resistance of rear speaker behind panel if you never hear it make a noise. 50r. It’s probably ok though.

What happens when you disconnect that front sensor ? Fault code? Noise from rear when reverse selected and park brake off?  
Post #237313113th Jul 2024 1:32 am
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Discosimon888
 


Member Since: 12 Jul 2024
Location: Luton
Posts: 7

United Kingdom 2007 Discovery 3 TDV6 SE Auto Cairns BlueDiscovery 3

Thanks for the tips. I’ve just tried swapping front inner left and right sensors, and the fault stays with the location which rules out the sensor.

I don’t think the rear sounder is at fault, as I still get the initial beep from the back when selecting reverse, before the front comes on constantly.

I’ll order and ECU and try that - do you know if they are plug and play or do they need coding?  
Post #237315813th Jul 2024 1:03 pm
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Pete K
 


Member Since: 15 Jan 2016
Location: GL
Posts: 10669

England 2005 Discovery 3 TDV6 HSE Auto Rimini RedDiscovery 3

Plug and play.  
Post #237315913th Jul 2024 1:27 pm
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Discosimon888
 


Member Since: 12 Jul 2024
Location: Luton
Posts: 7

United Kingdom 2007 Discovery 3 TDV6 SE Auto Cairns BlueDiscovery 3

The saga continues…

I got a new ECU today, and still exactly the same (at least that rules out one problem).

I’m not sure whether to try a new front loom next, or I might try temporarily replacing the green wire to the problem sensor in the front loom. As the sensor is working (clicking) I am guessing that the black/brown power cables are ok.  
Post #237359019th Jul 2024 2:35 pm
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Pete K
 


Member Since: 15 Jan 2016
Location: GL
Posts: 10669

England 2005 Discovery 3 TDV6 HSE Auto Rimini RedDiscovery 3

Check you have power between black and brown.

Remove the trim on the right of the throttle and locate the parking sensor plug.
Check connectors are clean.

Then as you say, run a new wire in and see  
Post #237359919th Jul 2024 3:26 pm
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Discosimon888
 


Member Since: 12 Jul 2024
Location: Luton
Posts: 7

United Kingdom 2007 Discovery 3 TDV6 SE Auto Cairns BlueDiscovery 3

I don’t like to be beaten, but this one is getting the better of me!

I have ~12V between black and brown at the sensor.

I have ~9V between green and black, and around -2-3V between green and brown (I think that’s the right way).

I have cut the wires and run direct from the under headlight plug to each green black and brown and no difference. I have tried 4 different sensors in that location too. Also checked the plugs by the throttle pedal!

It must be the green wire - not sure if I have the heart to carry on investigations though. I guess next step is to run a wire direct from the green at the sensor to the green at the ECU.

Thanks for your help so far!  
Post #237368220th Jul 2024 8:31 pm
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Discosimon888
 


Member Since: 12 Jul 2024
Location: Luton
Posts: 7

United Kingdom 2007 Discovery 3 TDV6 SE Auto Cairns BlueDiscovery 3

One further (and final for tonight) thought, this started shortly after I was testing my trailer lights (so had the trailer connected).

Could there be any relevance here, as I know the parking sensors are somehow linked to the trailer towing control.

I have towed since and the trailer plug works fine - with dash light for trailer indicators fully operational.  
Post #237368520th Jul 2024 8:48 pm
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Discosimon888
 


Member Since: 12 Jul 2024
Location: Luton
Posts: 7

United Kingdom 2007 Discovery 3 TDV6 SE Auto Cairns BlueDiscovery 3

So, latest update…

I had a bright idea last night, that if I cut the green wire (inner front right - problem sensor according to the diagnostic) next to the sensor ECU and connect it to the yellow wire (inner front left) then it should at least give me sensors back even if the front right inner wasn’t actually doing anything. Just tried this, and no bloody difference. Same beep, and still saying front right inner 0mm! I’m giving up now, and will live with it. Next step would be a new front loom and all new sensors I think - but I dislike firing the parts cannon at problems.  
Post #237370021st Jul 2024 8:48 am
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Pete K
 


Member Since: 15 Jan 2016
Location: GL
Posts: 10669

England 2005 Discovery 3 TDV6 HSE Auto Rimini RedDiscovery 3

I would imagine the system requires one sensor per input, but it was worth ago.

Try:

1) leaving the green wire disconnected. See if you now get a fault code for that sensor? Will the system operate?

2) With the GAP IID you can configure the CCF to state only rear sensors fitted. That should get you a working rear system.

3) As you say, temporarily run a wire front to back, replacing the green wire and just see if that fixes the issue. if it does, work out if the faulty wire is forward of the connector near the throttle pedal or rearward.  
Post #237370721st Jul 2024 10:42 am
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