Mr Bacchus
Well-known member
- Joined
- 26 Oct 2012
- Messages
- 303
I know there are many threads on this subject but I have not yet had any luck with my own problem so I thought I would start a thread, maybe it may help others with a similar problem. It's a bit long winded!
I am trying to fix a problem with the ABS and PDAS warning lights illuminating accompanied by 16 warning alarm bleeps! I have had this problem for approx. 18 months or so, at first it used to happen consistently but random at the point of activation i.e. at start, after driving for short while, after driving for a long while but now it happens 99% of the time as soon as I start the car.
The ABS when road tested seems to work, meaning I get the pulsing brake pedal under heavy braking. My immediate issue is that I have my MOT test due early November and this condition will result in a fail. Last November, when the problem was more intermittent, my friendly MOT tester passed the car only after he tried for a few times to get the car to run without the lamps/buzzer. I quite rightly will not be so lucky this time!
By the way, the AS book suggests wheel speed sensors or differential locks could cause these lamps to illuminate (although I have not read anything anywhere that mentions 16 bleeps!)
Here is a summary of my troubleshooting so far (in no particular order). I have relied mainly on the Adrian Streather book and Porsche workshop manuals for guidance.
- Removed, opened, examined and cleaned both accelerometers – visually okay but not yet tested as described in AS book.
- Check battery voltage at key off – 12.7 v (should be approx. 12.6 v)
- Checked battery voltage at idle – 13.85 v (should be 13.8 ~ 14.4, so on the low side)
- Bypassed relay R34 (the ABS/PDAS over-voltage protection relay)
- Cleaned the ABS control unit multi-pin connector
- Removed and cleaned the main battery earth cable connection to chassis
- Tried the 'water mist the engine bay in the dark whilst running' test to check for arcing.
- Checked and cleaned all electrical connections to ABS/PDAS components in the frunk area i.e. pump, dual solenoid valve, ABS hydraulic unit, reservoir.
- Topped up the hydraulic fluid a teeny bit (this oil has been changed annually since I bought the car) although I am sure it was fine before topping up.
- Checked all wheel speed sensor resistances at the terminals on the ABS multi-pin connector as described in the AS book – all 1000 ohms (should be 600 ~ 1600)
- Replaced both coils (I was doing this anyway)
- Replaced both dizzy caps (I was doing this anyway)\
- To the best of my knowledge no error codes present at last service in January.
Now it gets more interesting...
I discovered the left rear wheel speed sensor link-harness (from sensor connector to connector on main harness) was quite badly damaged. A replacement is £200 from OPC so I have made my own repair. The harness continuity checks out good after the repair and the wheel sensor resistance checks described above were made after the repair so in theory it should be fine but I am still suspicious of this part.
I today checked the resistance across the pins of each valve on the ABS control unit using the method described in the AS book. The resistance across pins 1 and 3 (lateral lock) should be 2 ~ 4 ohms but I measured 7 ohms. The resistance across pins 2 and 4 (longitudinal lock) should also be 2 ~ 4 ohms but I could not measure any resistance here.
Correction - I measured approx 5 ohms across these pins so assume okay. The AS book is a little misleading IMO as it shows the image of the connector on the hydraulic unit as well as the dual solenoid valve - I checked the wrong pins.
So I have two suspect components, one relating to speed sensors and one to diff locks. I can eliminate one quickly by spending £200 on a harness but I rather not if it is not necessary and the other could me much more time consuming and expensive! Maybe the I have two problems and they are multiplying up the alarm bleeps
My next step, hopefully tomorrow, will be more troubleshooting of the ABS hydraulic unit valve block using the Porsche manuals very detailed procedures.
Only one question for now, does anyone know if it is possible to replace the solenoid block of the ABS hydraulic unit (assuming the relays test good) or does the whole unit need to be replaced – gulp!
Enough for now, I'm off out to celebrate my birthday.
Steve
I am trying to fix a problem with the ABS and PDAS warning lights illuminating accompanied by 16 warning alarm bleeps! I have had this problem for approx. 18 months or so, at first it used to happen consistently but random at the point of activation i.e. at start, after driving for short while, after driving for a long while but now it happens 99% of the time as soon as I start the car.
The ABS when road tested seems to work, meaning I get the pulsing brake pedal under heavy braking. My immediate issue is that I have my MOT test due early November and this condition will result in a fail. Last November, when the problem was more intermittent, my friendly MOT tester passed the car only after he tried for a few times to get the car to run without the lamps/buzzer. I quite rightly will not be so lucky this time!
By the way, the AS book suggests wheel speed sensors or differential locks could cause these lamps to illuminate (although I have not read anything anywhere that mentions 16 bleeps!)
Here is a summary of my troubleshooting so far (in no particular order). I have relied mainly on the Adrian Streather book and Porsche workshop manuals for guidance.
- Removed, opened, examined and cleaned both accelerometers – visually okay but not yet tested as described in AS book.
- Check battery voltage at key off – 12.7 v (should be approx. 12.6 v)
- Checked battery voltage at idle – 13.85 v (should be 13.8 ~ 14.4, so on the low side)
- Bypassed relay R34 (the ABS/PDAS over-voltage protection relay)
- Cleaned the ABS control unit multi-pin connector
- Removed and cleaned the main battery earth cable connection to chassis
- Tried the 'water mist the engine bay in the dark whilst running' test to check for arcing.
- Checked and cleaned all electrical connections to ABS/PDAS components in the frunk area i.e. pump, dual solenoid valve, ABS hydraulic unit, reservoir.
- Topped up the hydraulic fluid a teeny bit (this oil has been changed annually since I bought the car) although I am sure it was fine before topping up.
- Checked all wheel speed sensor resistances at the terminals on the ABS multi-pin connector as described in the AS book – all 1000 ohms (should be 600 ~ 1600)
- Replaced both coils (I was doing this anyway)
- Replaced both dizzy caps (I was doing this anyway)\
- To the best of my knowledge no error codes present at last service in January.
Now it gets more interesting...
I discovered the left rear wheel speed sensor link-harness (from sensor connector to connector on main harness) was quite badly damaged. A replacement is £200 from OPC so I have made my own repair. The harness continuity checks out good after the repair and the wheel sensor resistance checks described above were made after the repair so in theory it should be fine but I am still suspicious of this part.
I today checked the resistance across the pins of each valve on the ABS control unit using the method described in the AS book. The resistance across pins 1 and 3 (lateral lock) should be 2 ~ 4 ohms but I measured 7 ohms. The resistance across pins 2 and 4 (longitudinal lock) should also be 2 ~ 4 ohms but I could not measure any resistance here.
Correction - I measured approx 5 ohms across these pins so assume okay. The AS book is a little misleading IMO as it shows the image of the connector on the hydraulic unit as well as the dual solenoid valve - I checked the wrong pins.
So I have two suspect components, one relating to speed sensors and one to diff locks. I can eliminate one quickly by spending £200 on a harness but I rather not if it is not necessary and the other could me much more time consuming and expensive! Maybe the I have two problems and they are multiplying up the alarm bleeps
My next step, hopefully tomorrow, will be more troubleshooting of the ABS hydraulic unit valve block using the Porsche manuals very detailed procedures.
Only one question for now, does anyone know if it is possible to replace the solenoid block of the ABS hydraulic unit (assuming the relays test good) or does the whole unit need to be replaced – gulp!
Enough for now, I'm off out to celebrate my birthday.
Steve