P38A speedo not working

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storm said:
I have 'ABS Fault' garage said fix speedo ! I have fitted 2 new front ABS sensors
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Garage are arseholes. Speedo is driven by signals from ABS sensors if they ain't working neither will the speedo. Make sure sensors are pushed in until they touch reluctor rings. The gap will be set when the wheels turn. Check the connections. The problem is with the sensors.
 
wammers said:
Garage are arseholes. Speedo is driven by signals from ABS sensors if they ain't working neither will the speedo. Make sure sensors are pushed in until they touch reluctor rings. The gap will be set when the wheels turn. Check the connections. The problem is with the sensors.
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I did think that, they cleared some faults off, but their computer would not talk to the ABS system to identify the problem or which sensor(s) were faulty.
Do you know the part nos for the rear sensors? or can the be tested?
Many thanks
 
storm said:
I did think that, they cleared some faults off, but their computer would not talk to the ABS system to identify the problem or which sensor(s) were faulty.
Do you know the part nos for the rear sensors? or can the be tested?
Many thanks
Click to expand...

You can check the sensors with a multi meter. Make sure they have continuity through them. When set to resistance that should change when a metal object is placed near tip. With ignition on check for 5 volts on sensor feed lines. Needs proper diag on it to check ABS. Do you not know anyone with a Nanocom? Maybe someone local to you on here who could read the system for you. STC2786 or STC2921 front. You really don't want to know how much genuine STC2787 or STC2922 rears are.
 
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wammers said:
You can check the sensors with a multi meter. Make sure they have continuity through them. When set to resistance that should change when a metal object is placed near tip. With ignition on check for 5 volts on sensor feed lines. Needs proper diag on it to check ABS. Do you not know anyone with a Nanocom? Maybe someone local to you on here who could read the system for you.
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I don't know anyone with Nanocom. If I replace the rear sensors, will the fault clear itself or will I have to get it clear via diagnostics some where?
 
storm said:
I don't know anyone with Nanocom. If I replace the rear sensors, will the fault clear itself or will I have to get it clear via diagnostics some where?
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Sorry i don't own a crystal ball. Fault should clear but may still be recorded. Check that all the sensors including your new ones have a circuit through them, i have had new ones with no continuity.
 
Saint.V8 said:
Is the speedo driven from one particular sensor on the P38 (the L322 is driven from one of the rears!)..??
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Don't know Ant. Think we have had ABS faults down to sensors were the speedo has not packed up so maybe just one. But which one i don't know.
 
No idea. I would imagine it would average all 4. It kicks out a fault when 1 or 2 are out of range of the others so it must be checking them all against some average or similar.
 
wammers said:
You can check the sensors with a multi meter. Make sure they have continuity through them. When set to resistance that should change when a metal object is placed near tip. With ignition on check for 5 volts on sensor feed lines. Needs proper diag on it to check ABS. Do you not know anyone with a Nanocom? Maybe someone local to you on here who could read the system for you. STC2786 or STC2921 front. You really don't want to know how much genuine STC2787 or STC2922 rears are.
Click to expand...

Hi Wammers, I finally got round to checking to see if I had 5 volts on the ABS feed wires, but could not get any readings (ignition was on). Tried to follow wires back, but lost them in the looms. Fuse box connections look clean underneath & fuses are ok. I don't know where to look now!
 
storm said:
Hi Wammers, I finally got round to checking to see if I had 5 volts on the ABS feed wires, but could not get any readings (ignition was on). Tried to follow wires back, but lost them in the looms. Fuse box connections look clean underneath & fuses are ok. I don't know where to look now!
Click to expand...
Apart from where the plug into the sensors all the ABS sensor feed wires go straight back to the ABS ECU. If you can't get 5 volts at any of them with ignition on (you could try with engine running) then ABS ECU is favourite culprit. Did you look at relay 2 in engine bay fuse box? That powers ABS ECU.
 
I've got a nanocom but am abroad at the moment won't b back till wkend will meet u sat or Sunday I've u want to use it I've it will work on your car mines 4.6 pm me
 
wammers said:
Apart from where the plug into the sensors all the ABS sensor feed wires go straight back to the ABS ECU. If you can't get 5 volts at any of them with ignition on (you could try with engine running) then ABS ECU is favourite culprit. Did you look at relay 2 in engine bay fuse box? That powers ABS ECU.
Click to expand...
Didn't try with engine running, so will try that. I did swap over a couple of relays, just in case, but no luck.
 
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