Traction Lamp on a C4
08-28-2001, 03:59 PM
#1
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Traction Lamp on a C4
In the three days I've owned my '91 C4, the traction control lamp (as well as the ! lamp) both come on and stay on for at least 10-30 seconds after the engine has been started when cold. Twice, I tried to drive the car with the lamps on, and it made a horrible clunking noise from the driveline (wheel area). After the lamps finally went out, the car ran fine.
Is it normal for these lamps to stay on for 10-30 seconds after a cold engine start? Why or why not?
Is it normal for these lamps to stay on for 10-30 seconds after a cold engine start? Why or why not?
08-29-2001, 05:28 PM
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I'd be interested in finding out this, as my 90 C4 does the same from time to time except it stays on for a few mins. It happened outside a porsche main dealers last month and i popped in for some advice.
The guy that came out topped up my brake fluid (seemed strange to me) but low and behold after a few hundred yards it went out!
:-( Unfortunatly it's happened again since though, and the brake fluid seems topped up fine.
I think i read somewhere on here that incorrect tyres can cause it to come on but i maybe wrong!
The guy that came out topped up my brake fluid (seemed strange to me) but low and behold after a few hundred yards it went out!
:-( Unfortunatly it's happened again since though, and the brake fluid seems topped up fine.
I think i read somewhere on here that incorrect tyres can cause it to come on but i maybe wrong!
08-30-2001, 08:13 AM
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This is a very complex issue which is very hard to deal with unless the whole story is posted. The questions asked need hundreds of words to answer. However I will tell you how a C4 acts on start up and why.
The PDAS Warn Lamp (Porsche dynamic allwheel system) known as Traction Control and does not control the AWD which is mechanical will come on when you apply power and will stay on after start with the Brake Pressure Warn Light for anywhere between 20 and 60 seconds.
WHY!!. The C4 has a hydraulic pump which must pressurise 23 metres of hydraulic line. This takes time. Depending on the age of the C4, the age of the pump, the charge level of the battery, how old the brake fluid is, how much charge is still in the accumulator (not rechargeable) controls the time factor.
The PDAS warn lamp on its own with the Brake Pressure Warn Lamp is telling you the C4 driver that the system is not available because the hydraulic pressure it too low.
If a PDAS system failure is detected the ABS warn lamp will also come on.
A PDAS warn on its own is telling you the brake hydraulic system is not up to pressure.
Reasons: Low brake fluid. Pump not running fast enough, leak in the system or a VERy BAD BRAKE BLEED has been carried out. Aged brake fluid also can cause this problem. As it ages it becomes hard to compress. Needs to be changed with the correct type DOT 4 every two years or 20,000klms whichever comes first. More often if you race or DE.
Check for contaminated connectors on the brake fluid tank sensor. Water around these contacts can cause this problem.
Make sure the tank lid is on correctly. Contaminated sensor probe, caused by dirty fluid.
However getting back to the system on start. The PDAS and BRAKE WARN LAMPS should be on for a period of time after start.
Incorrect tyres can cause problems but only after 40kph. Problems after start before you move off are normally caused by low battery. Why is the battery low,
Alternator failure
Regulator failure
Battery Failure
Current Drain.
Ciao,
Adrian
911C4
The PDAS Warn Lamp (Porsche dynamic allwheel system) known as Traction Control and does not control the AWD which is mechanical will come on when you apply power and will stay on after start with the Brake Pressure Warn Light for anywhere between 20 and 60 seconds.
WHY!!. The C4 has a hydraulic pump which must pressurise 23 metres of hydraulic line. This takes time. Depending on the age of the C4, the age of the pump, the charge level of the battery, how old the brake fluid is, how much charge is still in the accumulator (not rechargeable) controls the time factor.
The PDAS warn lamp on its own with the Brake Pressure Warn Lamp is telling you the C4 driver that the system is not available because the hydraulic pressure it too low.
If a PDAS system failure is detected the ABS warn lamp will also come on.
A PDAS warn on its own is telling you the brake hydraulic system is not up to pressure.
Reasons: Low brake fluid. Pump not running fast enough, leak in the system or a VERy BAD BRAKE BLEED has been carried out. Aged brake fluid also can cause this problem. As it ages it becomes hard to compress. Needs to be changed with the correct type DOT 4 every two years or 20,000klms whichever comes first. More often if you race or DE.
Check for contaminated connectors on the brake fluid tank sensor. Water around these contacts can cause this problem.
Make sure the tank lid is on correctly. Contaminated sensor probe, caused by dirty fluid.
However getting back to the system on start. The PDAS and BRAKE WARN LAMPS should be on for a period of time after start.
Incorrect tyres can cause problems but only after 40kph. Problems after start before you move off are normally caused by low battery. Why is the battery low,
Alternator failure
Regulator failure
Battery Failure
Current Drain.
Ciao,
Adrian
911C4
08-30-2001, 08:16 AM
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Dear Robert,
As I told you in another forum. The horrible clunking noise you are hearing is because one or both of the differential locks is engaged and it shouldn´t be.
Ciao,
Adrian
911C4
PS: These are hydro-mechanical clutch devices activated by hydraulic pressure (180 bar). The PDAS/ABS Control activates the solenoid valve which supplies the pressure. Maybe this valve is stuck in the open position pressurising the lines and activating the diff locks.
As I told you in another forum. The horrible clunking noise you are hearing is because one or both of the differential locks is engaged and it shouldn´t be.
Ciao,
Adrian
911C4
PS: These are hydro-mechanical clutch devices activated by hydraulic pressure (180 bar). The PDAS/ABS Control activates the solenoid valve which supplies the pressure. Maybe this valve is stuck in the open position pressurising the lines and activating the diff locks.
08-30-2001, 10:08 AM
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Dear Robert,
When you lock the differential (button near the gearbox) and while running (<40 km/h) you try to turn the steering wheel you will hear an horrible clunking noise. This is normal, the differential is locked.
It happens to me that sometimes the traction light and the ABS light come on after the engine has been started when cold. But the differential is not locked, no clunking noise when I turn. These light turn off when I reach 40 km/h.
Ciao,
Tito
When you lock the differential (button near the gearbox) and while running (<40 km/h) you try to turn the steering wheel you will hear an horrible clunking noise. This is normal, the differential is locked.
It happens to me that sometimes the traction light and the ABS light come on after the engine has been started when cold. But the differential is not locked, no clunking noise when I turn. These light turn off when I reach 40 km/h.
Ciao,
Tito
08-31-2001, 03:47 AM
#6
Robert:
Your car is the same age and type as mine, but mine only has 22K on it. This is NORMAL. Don't be alarmed by it. Worry about it if it takes 2 minutes for it to go away.
As Adrian pointed out, it takes time for the system to pressurize, and for that matter, for the system to complete it's diagnostics. This is NOT unusual, really, on a number of high performance cars, and I suppose for some non-high performance cars as well. Change your start up habits....turn the engine on first THEN buckle the seat belts, and do whatever else you need to do. Thirty seconds really isn't much time.
Bill Wagner
Your car is the same age and type as mine, but mine only has 22K on it. This is NORMAL. Don't be alarmed by it. Worry about it if it takes 2 minutes for it to go away.
As Adrian pointed out, it takes time for the system to pressurize, and for that matter, for the system to complete it's diagnostics. This is NOT unusual, really, on a number of high performance cars, and I suppose for some non-high performance cars as well. Change your start up habits....turn the engine on first THEN buckle the seat belts, and do whatever else you need to do. Thirty seconds really isn't much time.
Bill Wagner
08-31-2001, 04:29 AM
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The PDAS/ABS undertakes two self tests.
The first after start takes only 7 seconds.
The second takes the time it take you to get to 40kph.
All warn lights and little yellow leds should be out before driving off. You can drive off if the PDADS/ABS Warn Lights are on and the yellow led is on STEADY. This is actually a voltage problem. DO NOT drive off if the yellow led is flashing because this is teling you the diff locks either or, or both are engaged (there are two diff locks) but the traction control program has not been activated. This is quite different to activating the traction control program and driving off.
If the lights including the brake warn light is still on after 60 seconds take care. The hydraulic pump which you can clearly hear running will overheat and fail. It is designed as an intermittant pump not a constant running pump. 2 minutes and the thing will burn out.
The first item I would do if these problems keep occuring. Once in a blue moon is quite normal but if it is every day I would replace the brake fluid and get a complete power bleed carried out. The brake fluid breaks down, it is actually damaged by the hydraulic pump. It is called Fluid Shearing. The brake fluid can also be contaminated by water.
Ciao,
Adrian
911C4
The first after start takes only 7 seconds.
The second takes the time it take you to get to 40kph.
All warn lights and little yellow leds should be out before driving off. You can drive off if the PDADS/ABS Warn Lights are on and the yellow led is on STEADY. This is actually a voltage problem. DO NOT drive off if the yellow led is flashing because this is teling you the diff locks either or, or both are engaged (there are two diff locks) but the traction control program has not been activated. This is quite different to activating the traction control program and driving off.
If the lights including the brake warn light is still on after 60 seconds take care. The hydraulic pump which you can clearly hear running will overheat and fail. It is designed as an intermittant pump not a constant running pump. 2 minutes and the thing will burn out.
The first item I would do if these problems keep occuring. Once in a blue moon is quite normal but if it is every day I would replace the brake fluid and get a complete power bleed carried out. The brake fluid breaks down, it is actually damaged by the hydraulic pump. It is called Fluid Shearing. The brake fluid can also be contaminated by water.
Ciao,
Adrian
911C4