Check Engine Light
12-01-2003, 07:28 AM
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Check Engine Light
I am having a problem with my 2000 1.8TQMS and wonder if anyone else has experienced it and has a hint or solution:
About 6 or 8 months ago, the check engine light came on. The car hiccuped once, but has been fine ever since. I had a friend hook up an OBD reader and found a code for "secondary air intake". He reset the code and the car had trouble for a while (more hiccuping) and then was fine. After about 5 or 6 starts, the check engine light came on again. This time, we discovered what had been making a hissing noise that I had noticed -- a leaky vacuum hose leading into a valve on the intake manifold. We replaced the hose and reset the code. After another five or six starts, the light came on again. I took it into a mechanic and he noticed that an air pump by the right headlight was coming on and making a lot of unnecessary blowing, and then discovered another leaky hose leading into an emissions-related sensor near the firewall. He replaced that one, but the light still comes on and so does the pump. He said that the pump (which sounds alot like a vacuum cleaner) is related to the secondary air intake (an emissions thing, he says). It seems to me that there is probably another leak somewhere in this vacuum system, but I haven't been able to find it yet. Performance has not been affected, and the vacuum cleaner-sounding pump usually stops pumping after 30 seconds (I think it just gives up).
Has anyone had this problem before?
Thanks for the help,
Chris
About 6 or 8 months ago, the check engine light came on. The car hiccuped once, but has been fine ever since. I had a friend hook up an OBD reader and found a code for "secondary air intake". He reset the code and the car had trouble for a while (more hiccuping) and then was fine. After about 5 or 6 starts, the check engine light came on again. This time, we discovered what had been making a hissing noise that I had noticed -- a leaky vacuum hose leading into a valve on the intake manifold. We replaced the hose and reset the code. After another five or six starts, the light came on again. I took it into a mechanic and he noticed that an air pump by the right headlight was coming on and making a lot of unnecessary blowing, and then discovered another leaky hose leading into an emissions-related sensor near the firewall. He replaced that one, but the light still comes on and so does the pump. He said that the pump (which sounds alot like a vacuum cleaner) is related to the secondary air intake (an emissions thing, he says). It seems to me that there is probably another leak somewhere in this vacuum system, but I haven't been able to find it yet. Performance has not been affected, and the vacuum cleaner-sounding pump usually stops pumping after 30 seconds (I think it just gives up).
Has anyone had this problem before?
Thanks for the help,
Chris
12-01-2003, 07:42 AM
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The secondary air pump might be failing causing it to come on when it should not.
The pump usually comes on when the car is cold started and will only stay on for 30-60 seconds at a time.
12-01-2003, 07:44 AM
#3
if its very loud on startup, it could be a shot pump = expensive.
tell you mechanic to check this valve too.
from audi tech tips:
In the event you have an A4 1.8T with engine code ATW with the DTC of 16795 - Secondary Air Injection system, Incorrect flow Detected, a leaking Combination valve could be the problem. A leaking valve causes exhaust gas to enter the secondary air system. The water from exhaust condensation travels through the entire secondary air injection system and if the temperature drops below 0 degrees Celsius the water will freeze. In most cases the water causes the air pump to corrode. Inspecting the combination valve will reveal the problem. If the Intake side of the valve is black, exhaust has entered the secondary air injection system.
from audi tech tips:
In the event you have an A4 1.8T with engine code ATW with the DTC of 16795 - Secondary Air Injection system, Incorrect flow Detected, a leaking Combination valve could be the problem. A leaking valve causes exhaust gas to enter the secondary air system. The water from exhaust condensation travels through the entire secondary air injection system and if the temperature drops below 0 degrees Celsius the water will freeze. In most cases the water causes the air pump to corrode. Inspecting the combination valve will reveal the problem. If the Intake side of the valve is black, exhaust has entered the secondary air injection system.
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