MY 1998 AUDI A6 ESTATE V6 2.5 TDI AUTO RUNS FINE FOR SEVERAL HOURS THEN AFTER A STOP IT SUDDENLY GOES INTO LOW POWER LIMP HOME MODE (5000RPM TO REACH ONLY 50MPH). I HAVE CHECKED AND CLEANED THE TURBO AND EGR AND BOTH FINE. CANNOT FIND ANY AIR VACUUM LINE LEAKS. 245,000 MILES. 4TH CAM BELT. NORMALLY IT RUNS AT 80MPH AT 38MPG. JUST SOMETIMES IT GOES LOW POWER

Service the anti lock brake system and have a diagnostic test done to find out exactly what parts are giving you the trouble codes.

Is it not shifting into third gear (meaning you're at redline and the car won't shift), or is there not enough power to get the car going fast enough to warrant going into third gear? Have you checked to see if the car is in limp mode?

In the most cases for Audi 2.0 TDI the turbocharger is responsible for engine losing power.
The car goes in "limp home" mode!!!
After scan the EDC-15P engine control unit with a VAG or KTS -BOSCH diagnosis tool you will find this: Fault code: P1557-Turbo Boost pressure control exceeded
1. Engine stopped and ignition switch off. Check all pneumatic connections and hoses between turbocharger actuator = pressure unit for boost-pressure control, boost-pressure control solenoid valve, vacuum reservoir, EGR control solenoid valve, intake-manifold flap solenoid valve, EGR valve with throttle - part of intake manifold. Also the vacuum connection between tandem pump and brake booster. If you find something wrong replace parts. If not go to step 2.
2. Extract the hose of the turbocharger actuator = pressure unit for boost-pressure control part of turbocharger. Instead of the original hose you must place another 1 meter long hose with the same inside diameter, and then you check to inspire yourself the air from the other one extremity of this hose. The mechanical connecting rod of the turbocharger actuator must have a smooth and whole motion. If you can do that with your mouth, then you must replace the boost-pressure control solenoid valve. If you can not reach this with your mouth, then you go to step 3.
3. This is the most difficult work. The problem is that the soot particles deposits inside the turbocharger plugging the variable nozzle geometry mechanism = adjustable vanes of the turbine. If the turbocharger actuator is not able to adjust the turbine vanes the charge air pressure increase too much and ECU (engine control unit) go in "limp mode" = engine protection software. As a result the "limp home" mode engine still running until you turn the engine off (ignition switch off) and back on when the "limp mode" is deactivated, but the fault still remain in ECU memory!
4. You must be able to extract the turbo from the engine and then to disassemble the turbocharger, clean inside adjustable vanes mechanism and refit all.

16619 -Engine boost condition - Limit not reached. Check intake hoses/ connections for leaks. Check Turbo charger waste gate regulating valve/ waste gate working correctly. Must move freely when accelerating, won't achieve full boost if waste gate sticking open. Check Turbo impeller turning freely, oil feed pipe for turbo can get blocked causing impeller to seize. Engine compact, not easy to access these components.

Audi A4 1.8 quattro 1997 automatic transmission does not change gears sometimes. It revs very high but the gear seems to be put in neutral

I'm afraid to replace it is a cambelt off job. Had mine done on a 2.5tdi a4 avant so had cambett waterpump and tensioner replaced with thermostat.

hi,i'm ck .my audi c5 2.4 model 2001, when put on D while driving, it go to neutral?

I can help you to fix this problem. "Fault code: P1557 - Turbo Boost pressure control exceeded"
But I need some info from your engine:
- what type of engine do you have (engine code: ex.ALH, AJM, AWX, ...) or power in kW (PS)
- how many km (miles) are your car?

My e-mail adress is: [email protected]

where are the adjustment screws for the 2005 audi A6 headlights, my normal lights are way to high and the brights search the trees.

Your car goes in "limp mode"!!!
If you scan the EDC-15P engine control unit with a VAG or KTS -BOSCH diagnosis tool you will find this:
"Fault code: P1557 - Turbo Boost pressure control exceeded"
You must try follows if you are able to do this:
1. Engine stopped and ignition switch off. Check all pneumatic connections and hoses between turbocharger actuator = pressure unit for boost-pressure control, boost-pressure control solenoid valve, vacuum reservoir, EGR control solenoid valve, intake-manifold flap solenoid valve, EGR valve with throttle - part of intake manifold. Also the vacuum connection between tandem pump and brake booster. If you find something wrong replace parts. If not go to step 2.
2. Extract the hose of the turbocharger actuator = pressure unit for boost-pressure control part of turbocharger. Instead of the original hose you must place another 1 meter long hose with the same inside diameter, and then you check to inspire yourself the air from the other one extremity of this hose. The mechanical connecting rod of the turbocharger actuator must have a smooth and whole motion. If you can do that with your mouth, then you must replace the boost-pressure control solenoid valve. If you can not reach this with your mouth, then you go to step 3.
3. This is the most difficult work. The problem is that the soot particles deposits inside the turbocharger plugging the variable nozzle geometry mechanism = adjustable vanes of the turbine. If the turbocharger actuator is not able to adjust the turbine vanes the charge air pressure increase too much and ECU (engine control unit) go in "limp mode" = engine protection software. As a result the "limp mode" engine still running until you turn the engine off (ignition switch off) and back on when the "limp mode" is deactivated, but the fault ("Fault code: P1557 - Turbo Boost pressure control exceeded") still remain in ECU memory !!!
4. You must be able to extract the turbo from the engine and then to disassemble the turbocharger, clean inside adjustable vanes mechanism and refit all.
It is some work to do here, but after that you will be full satisfied! NO MORE "LIMP MODE"!!!
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It is a certified solution. Last year in July I made this turbocharger cleaning on my car - 2000 Audi A4 1.9 TDI 116 HP. After 25000 km my car runs like an authentic AUDI 1.9 TDI.