Abs fault ( the lemon strikes again)

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kermit_rr said:
There's 3 bleed nipples, one is right under the bulkhead and really hard to see
Click to expand...
Update :- My local garage/MOT station that I've used for the last 6 years has diagnosed a faulty front RH ABS sensor and/or faulty wiring. His kit doesn't diagnose it in any further depth. He didn't carry out any other work on the abs sensors in case it gave the "Landrover Specialist" an excuse to void the warranty by claiming someone else has fiddled with his work when I take it back on Monday. Brakes were not bled. Basically the ABS system is fighting the brake pedal and is counteracting my efforts to brake. Bit fed up of it all now. Don't know whether it is worth me taking the sensor out and reseating it again. Basically I have the same fault that i had originally after the 1st pair of sensors were fitted. Maybe it's a break in the loom between OSF sensor plug and ECU, which would explain why 2 sets of sensors haven't solved it.
 
I'm not an expert.. yet!!
But, from what i understand, there should be ~5v at the sensor connector. Someone else will confirm.
If that's correct, then it's the sensor, if no voltage or the wrong voltage, you need to check the wire to the ecu which i believe had no connections along the line.
 
kermit_rr said:
I'm not an expert.. yet!!
But, from what i understand, there should be ~5v at the sensor connector. Someone else will confirm.
If that's correct, then it's the sensor, if no voltage or the wrong voltage, you need to check the wire to the ecu which i believe had no connections along the line.
Click to expand...
c. 5.3v at each sensor connector (looking back towards the ECU) on mine.
c. 1.2 - 1.5 Kohms resistance across each sensor. Open cct ...its phucked, <1Kohms... also phucked.
At least, this has been my recent experience with these nasty little blighters.
 
kermit_rr said:
I'm not an expert.. yet!!
But, from what i understand, there should be ~5v at the sensor connector. Someone else will confirm.
If that's correct, then it's the sensor, if no voltage or the wrong voltage, you need to check the wire to the ecu which i believe had no connections along the line.
Click to expand...
is that 5v ac or dc ? and measured across the 2 sockets ?
 
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DanClarke said:
c. 5.3v at each sensor connector (looking back towards the ECU) on mine.
c. 1.2 - 1.5 Kohms resistance across each sensor. Open cct ...its phucked, <1Kohms... also phucked.
At least, this has been my recent experience with these nasty little blighters.
Click to expand...
When I tested the 2nd set of sensors they were both around 995-998 ohms and the 1st set were n/s/f 1100 ohms and o/s/f 995 ohms.
 
From nanocom;

Sensor voltage: This shows the DC Voltage for the front and rear wheel speed sensor. Expected values are between 2.0 to 2.4 Volts. The wheel speed sensors are different to the conventional wheel speed sensors used on other Land Rover products. Conventionally, wheel speed sensors have an interference fit with the hub or back plate. This positions the sensor close to a reluctor ring. The sensors used are incorporated into the inboard wheel bearing, on both front and rear hubs. This bearing assembly is a sealed unit and has no replaceable parts. Also different is the wire from the wheel speed sensor. Land Rover has, historically used a wheel speed sensor employing a signal wire inside a shielded earth wire. The new wheel speed sensors have a twisted pair of wires. This offers some electrical advantages over two straight wires. Such as the signal being less susceptible to electrical noise or interference and it generates less electrical noise, the wires can also be balanced together (similar electrical properties) to ensure voltage losses are minimized. Like a conventional wheel speed sensor, the signal created is an AC sine wave. This wave is generated in the inductive sensor by a sixty-tooth reluctor, machined into the wheel bearing inner race. The frequency of this signal supplies the ABS ECU with the information it needs to determine the speed of the individual wheels and is used in the calculation of vehicle speed or vehicle reference speed.
 
kermit_rr said:
From nanocom;

Sensor voltage: This shows the DC Voltage for the front and rear wheel speed sensor. Expected values are between 2.0 to 2.4 Volts. The wheel speed sensors are different to the conventional wheel speed sensors used on other Land Rover products. Conventionally, wheel speed sensors have an interference fit with the hub or back plate. This positions the sensor close to a reluctor ring. The sensors used are incorporated into the inboard wheel bearing, on both front and rear hubs. This bearing assembly is a sealed unit and has no replaceable parts. Also different is the wire from the wheel speed sensor. Land Rover has, historically used a wheel speed sensor employing a signal wire inside a shielded earth wire. The new wheel speed sensors have a twisted pair of wires. This offers some electrical advantages over two straight wires. Such as the signal being less susceptible to electrical noise or interference and it generates less electrical noise, the wires can also be balanced together (similar electrical properties) to ensure voltage losses are minimized. Like a conventional wheel speed sensor, the signal created is an AC sine wave. This wave is generated in the inductive sensor by a sixty-tooth reluctor, machined into the wheel bearing inner race. The frequency of this signal supplies the ABS ECU with the information it needs to determine the speed of the individual wheels and is used in the calculation of vehicle speed or vehicle reference speed.
Click to expand...

Reading that it looks like its talking about a later model car not a p38 as the regulator ring is on the drive shaft and not machined into the bearing inner race.
 
brianp38dse said:
Reading that it looks like its talking about a later model car not a p38 as the regulator ring is on the drive shaft and not machined into the bearing inner race.
Click to expand...
That's true, i hadn't realised/acknowledged what was written.. it's from the right document but it won't be the first discrepancy
 
kermit_rr said:
From nanocom;

Sensor voltage: This shows the DC Voltage for the front and rear wheel speed sensor. Expected values are between 2.0 to 2.4 Volts. The wheel speed sensors are different to the conventional wheel speed sensors used on other Land Rover products. Conventionally, wheel speed sensors have an interference fit with the hub or back plate. This positions the sensor close to a reluctor ring. The sensors used are incorporated into the inboard wheel bearing, on both front and rear hubs. This bearing assembly is a sealed unit and has no replaceable parts. Also different is the wire from the wheel speed sensor. Land Rover has, historically used a wheel speed sensor employing a signal wire inside a shielded earth wire. The new wheel speed sensors have a twisted pair of wires. This offers some electrical advantages over two straight wires. Such as the signal being less susceptible to electrical noise or interference and it generates less electrical noise, the wires can also be balanced together (similar electrical properties) to ensure voltage losses are minimized. Like a conventional wheel speed sensor, the signal created is an AC sine wave. This wave is generated in the inductive sensor by a sixty-tooth reluctor, machined into the wheel bearing inner race. The frequency of this signal supplies the ABS ECU with the information it needs to determine the speed of the individual wheels and is used in the calculation of vehicle speed or vehicle reference speed.
Click to expand...
I have never looked at the standing voltage, but the signal is certainly a wave form that will transition the standing voltage in a positive and a negative direction.
 
5v dc across loom pins with ignition on.
Think i'll take the sensor out and check the dimple for iron filings & scoring if its been in contact with the reluctor ring. It was inserted with firm finger pressure up to the reluctor ring - it didn't need to be knocked in, so I can't imagine that it wasn't far enough in and that it hasn't self set since installation. Does anyone know what the actual air gap is supposed to be ?
 
kermit_rr said:
Both mine needed to be tapped in, i used a plastic hammer.. you hear the tone change when it's in all the way. It should *just* touch the reluctor ring.
Click to expand...
The sensor should be a fairly easy push fit. It should be slid in until it touches the reluctor ring, air pressure will then push it back to set the gap when the wheel rotates. Obviously if the fit is too tight, it will not push back and is then likely to be damaged.
 
Datatek said:
The sensor should be a fairly easy push fit. It should be slid in until it touches the reluctor ring, air pressure will then push it back to set the gap when the wheel rotates. Obviously if the fit is too tight, it will not push back and is then likely to be damaged.
Click to expand...
So if the sensor remains in contact with the reluctor and air pressure has not set the correct gap, is that likely to throw the Abs light on ? My original question stands, what is the correct air gap in thousands of an inch ? I could then set it with a feeler gauge.
I can see where Wabco state "NOTE: After installation, there should be no gap between the sensor and the tooth wheel. During normal operation, a gap of up to 0.04-inch is allowable."
0.04" is equal to 1mm.
 

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Air pressure doesn't come in to it. You either press the sensor tip into a gap between the teeth and it pushes up slightly as it spins, or you press it onto a tooth and it's already in the right place
 
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