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Discussion Starter #1
Hi
I 2.0HDI 2002 Peugeot 307. The ABS and anti skid light has been on for a while and I have been meaning to get round to it but now coming up for the MOT so it has become a priority. I though it would be as normal remove sensors clean away the rust and all good. However this time its not looking so straight forward. I have put the code reader on the car and it tells me its the rear right sensor open circuit. I changed the sensor with a spare I had but still the same fault. I disconnected the left sensor and did another reading just to confirm I had the correct side and then the reader said left and right open circuit so I proved that I was on the correct side. I have made some basic measurements from the cable coming from the care and found the following:

Left hand (good side)
side key off 4.2Mohms in one direction and 5.1Mohms in other.
key on 3.7k ohms in one direction and 6.8K in the other.
23mV DC on the connector
Right side (faulty side)
Key off 3.9Mohms in one direction and 5.3 in the other
Key on 0.7Mohms in one direction and 0.8 in the other
9.7mV DC on the connector.

I am now thinking this looks like the ecu as if I had an open circuit I would not be measuring any thing? or perhaps a high resistance on the connector some where else?

Could any one help with this

Thanks in advance
Peter
 

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Don't understand the sentence "coming from the care"! and what the side key is but you have a high resistance I would say and that would indicate corrosion on a connector I would have thought.
 

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Discussion Starter #4
Sorry my doggy typing should read Car not care, Side should not be in front of Key.
I have removed the front bumper and traced the cables to the ECU. I found one of the cables to the faulty sensor open circuit about 75mm from the rear connector. I soldered in a new section of cable and reassembled as I need the car for work tomorrow and it was starting to rain (have to work on the driveway) but on testing lights still on and now the diagnostics says both rear sensors are faulty?
I will have to have another look after work tomorrow weather permitting.

Thanks for the response I will post what I find and the pinouts to the rear sensors later as this may help some one in the future working on this type of fault.

Regards
peter
 

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You might find that after you have moved the car above 5mph that the defect will clear as the abs will recheck all movement signals and if ok system resets.
Thanks for pointing out typing errors as sometimes I am not too sure its me misreading!
 

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Discussion Starter #6
Thanks for getting back to me I cleared the faults with the diagnostic tool and as you said when for a drive but no luck. The only thing I can think of is that I used a bit of 1.5mm twin and earth cable to poke into the sockets at the back of the car to get a connection. I wonder if I have spread the connectors in side so they are no longer making good contact with the plug on the sensors?

Pteer
 

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The ABS system does two checks. The initial check is to poll the sensors on each wheel, if these pass a continuity/resistance type test it will extinguish the ABS light. The second test is it monitors the rotational signal from each wheel when the car starts moving. If there is no signal or one which does not fall within set parameters when comparing with other wheels, it will put the ABS light on and disable the abs system. This fault is most often caused by faulty/damaged/dirty ABS rings on the hubs/sideshafts.
Your issue is related to the first check. Your wiring/wheel sensors have a basic fault so the ABS will be disengaged from the get-go and will not extinguish no matter how far you drive.
You can test the sensors by simply removing them and plugging into a different wheel, you do not have to mount them. You then scan the system. If the fault shifts position, you can bet the sensor is duff. If the fault does not shift, the issue is in the wiring and/or ABS ECU.
 
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