hello there this is my first post so i hope its in the right place .

so i have been lumbered with getting this thing fixed so will tell you what i know ..

car first came to me because of failed mot on power steering inoperative . i sent them away as power steering works fine . 

it turned out the fault was the warning lamp not coming with ignition on so car is back here . i thought ah the led will be gone ..stripped cluster down and led was literally gone like mia .. so i get the idea now .. put in new led and of course it is lit up constantly .. battery is good .charging system is good . fluid is correct level .. tried clearing codes with launch says cleared .light is still on .. tried angle reset and learning and light still on .

when key is turned on light flashes twice very quickly and stays on .. anyone have any ideas what direction to go in next ?p.s how many ohms should hall sensor gave across it ? am guesing 1.2 1.5k ish .. i will test it in the morning and see if 5v present .. am guessing steering should lose power assist if sensor bad anyway ? 

thanks in advance for any help with this ..

pete . 

 

It sounds like the pump ECU has failed, most likely due to moisture ingress and corrosion inside the pump on the PCB, you could simply swap out the pump for a secondhand unit, they're pretty common if it's a TRW unit.

Bear in mind the PAS system is completely self-contained, only the angle sensor and ECU in the pump control the PAS, so unless the wiring is faulty (unlikely) then one or the other will have failed, if the PAS starts working as soon as you turn the wheel then it's the pump, if the PAS is working all the time at a reduced level whenever the engine is running then it's probably the sensor.

so if i was to unplug the sensor it should behave just the same ? 

i would have thought clearing the codes should have put warning light out for a short time but never happened ... a new pump ecu would need coding wouldn't it ? 

i will try removing sensor first and see what happens . if it kills power assist i will try and diagnose pump ecu ... 

strange thing is abs fault light only comes on after disconnecting battery .. then no show after that . also another one i cant remember now ... makes me think it is cluster control chip playing up ...

Yes they need coding if replaced. Good general info here....

 

https://www.briskoda.net/forums/topic/186217-fabia-power-steering-problems/

 

ok i pulled sensor out and power steering still operating . light still on obviously ..

sensor tests open circuit between any of the pins .

checked voltage to sensor and zero volts to any wire . 

i can only presume the sensor should show about 15k ohms ish between 2 pins and power supply should be 5v . 

i could do with a complete schematic for the system so i can go through it in depth .. in the meantime i might just pull the pump out and strip its module down to give it a looking at . 

27 minutes ago, petehall347 said:

ok i pulled sensor out and power steering still operating . light still on obviously ..

sensor tests open circuit between any of the pins .

checked voltage to sensor and zero volts to any wire . 

i can only presume the sensor should show about 15k ohms ish between 2 pins and power supply should be 5v . 

i could do with a complete schematic for the system so i can go through it in depth .. in the meantime i might just pull the pump out and strip its module down to give it a looking at . 

 

I wouldn't bother, the sensor is definitely shot if it's all open circuit. Pump may be bad as well but I doubt it since it's working ok in limp-home mode.

what about the zero volts supply to sensor ? i expected 5v reference . 

It's a capacitive sensor if I remember right, so no measurable resistance isn't necessarily wrong. Have you extracted the sensor to visually inspect?

12 minutes ago, petehall347 said:

what about the zero volts supply to sensor ? i expected 5v reference . 

 

Sensor is a hall-effect device which generates a mV AC output, like a guitar pickup or an ABS sensor, it's basically a large coil of copper wire wrapped round a ferritic pole piece.

 

says trw on filler cap/dipstick . 

i have the sensor apart as far i dare . just checked it for ac and dc outputs whilst turning the wheel . nothing at all happening . but if this is capacitive that is expected i suppose ? 

pump has 68 ohms across 2 of the pins brown to black i think it was . or brown to green .. not that it means anything yet until i can see a schematic of the pump internals .

also pump has lots of corrosion that may well have spread inside it . 

on another note i figured out the abs light ... no abs fitted ...that is good news as i need a yellow led for steering fault light . i put a white one in for now . 

Good news on the ABS 'fix' 

I doubt you'll find a schematic of the pump internals published.

I'd guess at a PWM'd mosfet driven motor with control inputs of angle-sensor turn rate and vehicle speed (via CAN). 

Can you read the fault codes?

my scanner will say codes are stored but wont tell me what they are ..can also erase codes . 

am thinking i could test the sensor by reading capacitance on the data line out of the sensor when turning the wheel . 

i still think it needs a reference voltage as diagram shows it as live . annoyingly doesn't say whether its 5v or 12v . although i would expect 5v . 

3 hours ago, petehall347 said:

says trw on filler cap/dipstick . 

i have the sensor apart as far i dare . just checked it for ac and dc outputs whilst turning the wheel . nothing at all happening . but if this is capacitive that is expected i suppose ? 

pump has 68 ohms across 2 of the pins brown to black i think it was . or brown to green .. not that it means anything yet until i can see a schematic of the pump internals .

also pump has lots of corrosion that may well have spread inside it . 

on another note i figured out the abs light ... no abs fitted ...that is good news as i need a yellow led for steering fault light . i put a white one in for now . 

 

I wasn't aware that there were any Fabias without ABS, let alone ones with instrument clusters with an ABS warning light!

 

Either you have an incorrectly coded dash cluster or you do have ABS.

no abs at all .. no abs unit under the bonnet and no sensors on the hubs ... 

the warning light only comes on after battery disconnect and reconnect  then off after a few seconds then stays off . 

still need to get to the bottom of the steering fault . 

1 hour ago, sepulchrave said:

 

I wasn't aware that there were any Fabias without ABS, let alone ones with instrument clusters with an ABS warning light!

 

Either you have an incorrectly coded dash cluster or you do have ABS.

 

Yes there are Mk1 Fabias with no ABS.

15 minutes ago, TMB said:

 

Yes there are Mk1 Fabias with no ABS.

 

Wow, how revolting.

i sorted the led out now . robbed the abs one as its not used and its yellow ..just have to get it to go out now ..was going to strip the pump but decided to try a new sensor first . date on this one is 2007 so it could have gone bad . if that doesn't fix its off with the pump for a look inside it ..hoping its not buggered as pumps cost more than the car is worth .. sensors arent cheap either .as far as my scanner will read it the pump is ok but if i clear codes the light stays on . suppose it would if sensor bad . 

update .

been to local garage and used 2 different scanners . its looking like its the sensor no movement detected from sensor so will know tomorrow when new sensor arrives . 

update .

correct new sensor arrived .well not quite as wire was short and had to extend it . 

steering seems to feel better .took for a drive to garage cleared faults and now getting permanent fault "steering angle sensor reference voltage short to ground  01290    " i strongly suspect the pump now as same fault with both sensors .. 

anyone know where to test the reference voltage with a multi-meter ? 

Edited 1 June, 20179 yr by petehall347

Pin 1 of the 3-way sensor connector (on the pump)should have 5V relative to pin 2, I think

ok both outer pins are zero volts .centre is ground . tested engine off and running .

no pins are shorted to each other . am now expecting to find a blown 5v regulator inside the pump . or something similar ... 

Edited 1 June, 20179 yr by petehall347

Is cabin fusebox fuse 7 intact?

Edit: Actually, probably irrelevant, don't think there would be any steering assistance if that was blown.

 

 

 

Edited 1 June, 20179 yr by Wino

i checked fuse for fun .. pump is getting its 12v in and data lines look ok as far as i can see . 

if i had a schematic or even a wiring diagram with voltages it would make things easier . i dont like stripping things down for fun in case i break something thats ok to start with .