[flash]

i am prepping the white car to go out the door, and i have only 1 thing to fix first.  the speedometer just became non-operational a couple of days ago, and the anti-lock light stays on.  i am all but certain it is related to the speed sensor.  it is likely dirty, as i have found on other cars.

 

 

refresh my memory:

 

is the ABS / speed sensor on the front right or front left (driver or passenger side)?

 

also, does the ECU need to be disconnected to clear the fault memory (like in the case of the airbag).  i have the durametric, but it is not clearing the code.  i have not yet messed with the sensor, but initially it showed that fault code, i cleared the code, but the anti-lock light stays on.

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[MCL968]

I believe it takes the signal from the left front wheel ABS sensor. Does the Odo move?

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[flash]

nope.  it won't move unless the speedo does.  i'll be putting it in the air in the next day or so.  pretty sure it's just the sensor gummed up.  it happens on these cars.

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[unknown4u]

In my case the relay was the culprit.sometimes it works. Sometimes not. If you hit a bump everything workes fine again. No faultcodes at all and lights goes off and needle goes up.

That causes the problem. Easiest way to check all the sensors is to go to the abs module at the right footwell. Disconnect the connector and use an ossiloscoop. Check also if there is 12 volt.

Because the abs module is everytime when the ignition is switched of completly turned off the power. There are no fault codes stored.


But you can also have the problem with a sensor. The tip has it signal from the back of the rack and pinion.

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[flash]

back of the rack and pinion???  what sensor would be there?

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[Waylander]

Clean the terminals on the frequency multiplier in the fuse box,


The speedo and the abs get the reference signal from that


Also unplug and plug in G22 the abs relay a couple of times

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[flash]

frequency multiplier?  do we have a "different side of the pond" thing going on here?

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[flash]

never mind - found it

 

i'll check all that stuff out probably tomorrow.

 

regardless, this is going to be a pretty easy fix.

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[ds968]

Frequency multiplier ?! Sounds like a catholic or mormon family planning decree . Parrrump-pum . Sorry, could not resist .


Rack and pinion in tiptronics ? Huh ?

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[unknown4u]

Sorry wrong word. Differential. Can happen. Not my native language and someone was asking me at the time I wrote it down.

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[Waylander]

Ah you found the frequency multiplier, blimey I know something you dont that's rare


I had an issue with a friends 968 where the speedo would only show about 2/3 speed,

When his sat nav said he was doing 60 mph the speedo would show 40


I changed the multiplier for one I found on eBay and that fixed it straight away

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[flash]

no worries.  never even noticed that unit.  in 11 years i've never heard of a problem with it.  i'll check it out, probably today.

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[Bulti]

What does this unholy device look like??

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[flash]

what unholy device?  the freq multipier?  it's the G16 relay.  over $300.00 and only in germany

 

the antilock relay is almost $200.  the antilock sensor is almost $100.  at least those two are in the US.

 

cleaned contacts, cleaned sensor - no dice.  need to check the tip seonsor, but i suspect it is the ABS sensor, since the durametric first showed "speed sensor" as the fault.  looks like i need to order parts, and try them out to see if it fixes it.  this sucks.

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[968Syncro]

In my case the relay was the culprit.sometimes it works. Sometimes not. If you hit a bump everything workes fine again. No faultcodes at all and lights goes off and needle goes up

Exactly the same symptoms I had, and the cause was the ABS relay. 

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[flash]

i do not have this problem.  bumps have no effect.  it's just plain dead.

 

i sure wish there was some way to test this without having to buy parts

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[flash]

anybody know which pins to short on the ABS relay?

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[Waylander]

You can test the wheel sensors, multimeter across the sensor and spin the wheel as fast as you can by hand and you should see about .5v


Just can't remember if it's dc or ac. There is the connection on the strut in the little black connector there is another connection in the engine bay up near the strut towers


I would see if those are clean


If not I have a list of the pins to test the wheel sensors from the ECU plug


Right Front ECU Plug Pins 21 and 11

Front Left ECU Plug Pins 6 and 4

Rear Right ECU Plug Pins 24 and 26

Rear Left ECU Plug Pins 8 and 9

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[flash]

i guess i can put the car on stands, disconnect the sensor, and test those contacts.  that might tell me if i am getting voltage to the sensor, which would then eliminate the relay and converter.

 

i am pretty sure the pins you are calling out are for the brake sensors.

 

i have the 2 relays from the blue car being sent down here so i can test them in this car.  i'll clean the car up in the meantime, so no big deal on the lost time.

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[968Syncro]

Here is the ABS relay schematic, saved from my previous failed diagnostic work. 

 

I have no written description saved, but it looks like pins 87 (5) and 30 (7).

 

 

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