ABS fault help

[hipwell]

Hi guys.

Wondering if anybody can help with my abs fault before I have to give in and pay somebody to plug it in and get a code.

Abs light comes on at startup and doesn't go out, can also feel the pedal pulsing when braking.

So fault finding up to now..

I disconnected the rear sensors at the plugs next to the rear beam and pluged in the oscilloscope and spun the wheel.

Both rear wheels gave the same size sine wave reading so I'm fairly confident both sensors are functioning. Or is this not a good way to test them?

I did the same with the front right which also gave a solid sine wave, but stronger than the rears but I put this down to the different and rings front to rear.

I didn't test the front left as the Speedo works fine so can only assume the sensor is working correctly as I'm told front left is where the speed signal comes from as I have to gearbox Speedo

I need to check continuity from the sensors to the pump end of the wire but can't even see the bloody abs module. Where the hell is it?

 

[JB21]

Check the abs wiring located above the NSF a-frame underneath the car. Pull the plug and check voltage. Also check voltage on the front abs sensors.

The pump is located on the NS of the engine bay lower down, bit of a PITA to get to.

God i had fun trying to solve my issue on my old 182. Turned out to be the abs pump ecu, then a few days after replacing that the NSR sensor went costing £127.

The abs pump has just gone on my Octavia as well, lol.

 

[hipwell]

Check the abs wiring located above the NSF a-frame underneath the car. Pull the plug and check voltage. Also check voltage on the front abs sensors.

The pump is located on the NS of the engine bay lower down, bit of a PITA to get to.

God i had fun trying to solve my issue on my old 182. Turned out to be the abs pump ecu, then a few days after replacing that the NSR sensor went costing £127.

The abs pump has just gone on my Octavia as well, lol.

Might sound thick, but by A frame I take it you mean the A shaped thing attached to the back of the subframe? Does this need to come off to get to said wiring plug?

 

[JB21]

Yeah thats the one mate. The wire and plug is just tucked up above it, no need to remove anything.

 

[hipwell]

Yeah thats the one mate. The wire and plug is just tucked up above it, no need to remove anything.

Found it. Looks fine, disconnected it, no corrosion on any of the pins. (Why are there 8 pins when there's only 2 wires per rear abs sensor)

 

[JB21]

Front ABS sensor check next then...

 

[hipwell]

Well update.

Just been out with the voltmeter.

Both rear sensor are getting 4.7v at the rear connectors so the connectors must be good up to there.

So i checked both sensors resistance, one reads 1000ohm, the other reads open circuit, so I recon that's the culprit.

How can it give a reading on the oscilloscope but read open circuit on a resistance check?

 

[hipwell]

Is this likely to fit, it seems to match the OE rear right part number

https://m.onlinecarparts.co.uk/triscan-7659429.html

 

[JB21]

Does sounds like it mate yeah. And that sensor looks OK, just check the connectors match the one on the car before buying and also check the voltage on the fronts just to be sure. My advice from experience is get it on Clip and find out for sure. I went around the houses with mine throwing the parts cannon at it and Clip diagnosed the abs pump instantly. for the sake of £20 or if someone local has one then just beer tokens its worth it mate.

Hope you get it sorted as not sure if you know when the system is in fault the brake bias reverts to 50/50 and in emergency stop situations especially in the wet its lethal!

 

[Kermit the Van]

I’ve got exactly the same issue on mine. What is this ‘Clip’ thing that you speak of ?

 

[Kermit the Van]

Ok, stupid question asked before engaging the night of Google. Clip is diagnostic software. Next stupid question is links to reliable sources to get said diagnostic software ?

 

[Krarl]

I’ve got exactly the same issue on mine. What is this ‘Clip’ thing that you speak of ?

Renault diagnostic software/tool