Hi Guys some help with an ABS issue on my GTi Thanks
Replaced the bulb for the ABS warning light in the dash and it still does not come on when the ignition is switched on.
There is a 12 volt supply to the printed circuit. My understanding is that the light circuit is completed by terminal 27 on the ECU being the earth. If I disconnect the multi pin plug from the ABS ECU under the passengers seat and connect a 12 volt supply to pin 27 it does not make a circuit.
Sorry for being so long winded but my question is. Is the cable to pin No 27 just connected to earth somewhere on the car?
Thanks
JT
ABS warning light
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Jaba
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No that wont work. You need to earth pin 27 with the ignition on to get the light on. There are two circuits to earth the lamp and light it up one on pin 27 and the other pin 20 with a blocking diode (in the harness behind the glove box) between them then through the abs relay for the first few seconds. Earthing either of these pins should light up the bulb.
You mention 12v on the pc but the ABS light has its own 12v wire from the ignition switch. As far as I recall this 12v supply goes via a usually grotty 2 way brown connector in the engine bay near where the speedo cable appears.
I think it is not pin 27 which lights the bulb at turn on as pin 27 is used for an error condition. So a quick check is does it light up if you disconnect an abs sensor coax connector ?? NB use the second full on key position.
Hope this makes sense and helps.
You mention 12v on the pc but the ABS light has its own 12v wire from the ignition switch. As far as I recall this 12v supply goes via a usually grotty 2 way brown connector in the engine bay near where the speedo cable appears.
I think it is not pin 27 which lights the bulb at turn on as pin 27 is used for an error condition. So a quick check is does it light up if you disconnect an abs sensor coax connector ?? NB use the second full on key position.
Hope this makes sense and helps.
The Joy of BX with just one Citroën BX to my name now. Will I sing Bye Bye to my GTI or will it be Till death us do part.
Hi Jabba
Thanks for the reply. If I am correct then what you suggest in disconnecting a sensor will bring pin No 20 in to use as the earth. Will try this at the weekend.
I should have explained better my action/ thought trail.
1. ABS light does not come on.
2. Replace bulb with a known good bulb. No Joy
3. With ignition switched on check that there is a 12v supply to bulb (Terminal on pc) Yes
4. Study the book.
Says that pin 27 is the earth.
So (thoughts) Disconnect the multi pin connector to see if pin 27 is a good earth.
5. Switch on ignition.
6. Using a 12v test lamp connected to pin 2 (live) then to a good earth. "test lamp works"
7. Now using the test lamp connected to pin 2(live) then to pin 27 "test lamp does not work".
So that was my question how do I check that pin 27 is a good earth? Or am I missing something?
Thanks for the update that in fact pin 20 is the earth when the ignition is switched on and not 27 which is used when there is a fault.
Please feel free to comment/criticise/educate
Thanks
JT
Thanks for the reply. If I am correct then what you suggest in disconnecting a sensor will bring pin No 20 in to use as the earth. Will try this at the weekend.
I should have explained better my action/ thought trail.
1. ABS light does not come on.
2. Replace bulb with a known good bulb. No Joy
3. With ignition switched on check that there is a 12v supply to bulb (Terminal on pc) Yes
4. Study the book.
Says that pin 27 is the earth.
So (thoughts) Disconnect the multi pin connector to see if pin 27 is a good earth.
5. Switch on ignition.
6. Using a 12v test lamp connected to pin 2 (live) then to a good earth. "test lamp works"
7. Now using the test lamp connected to pin 2(live) then to pin 27 "test lamp does not work".
So that was my question how do I check that pin 27 is a good earth? Or am I missing something?
Thanks for the update that in fact pin 20 is the earth when the ignition is switched on and not 27 which is used when there is a fault.
Please feel free to comment/criticise/educate
Thanks
JT