Crack-prone vacuum hose turning on the check engine light (2000-2002)
06-23-2004, 10:19 PM
#1
Crack-prone vacuum hose turning on the check engine light (2000-2002)
Don't know if this has been covered before, but a crack-prone vacuum hose may turn on your check engine light. An improved replacement hose is available, and was installed on 2002 cars starting with the VIN which ends in 4D2N007900.
The problematic hose is prone to crack near the secondary air injection valves it controls, and is covered with braided cloth. (Secondary air injection pumps air into the exhaust after cold starts to warm up faster the catalysts.) The improved hose has molded rubber ends. Audi of America published a Technical Bulletin describing the problem, and the improved replacement part. This being Audi, you get to pay to fix the acknowledged engineering weakness. A change in policy, taken to extremes, might cause Audi to replace control arms, tie rod ends, transmissions, and eventually experience Lexus-like resale value and customer satisfaction.
The technical bulletin number is 01-03-08. It says the hose failure can cause trouble codes about secondary air injection flow, random/multiple cylinder misfire, and bank 1 long term multiplicative fuel trim too lean.
I got secondary air injection trouble codes this morning, and sure enough the hose was cracked near both valves. This is at about 80k miles. It seems that the hose breaking is a question of "when" not "if", so if your car has it, you may as well replace it.
The problematic hose is prone to crack near the secondary air injection valves it controls, and is covered with braided cloth. (Secondary air injection pumps air into the exhaust after cold starts to warm up faster the catalysts.) The improved hose has molded rubber ends. Audi of America published a Technical Bulletin describing the problem, and the improved replacement part. This being Audi, you get to pay to fix the acknowledged engineering weakness. A change in policy, taken to extremes, might cause Audi to replace control arms, tie rod ends, transmissions, and eventually experience Lexus-like resale value and customer satisfaction.
The technical bulletin number is 01-03-08. It says the hose failure can cause trouble codes about secondary air injection flow, random/multiple cylinder misfire, and bank 1 long term multiplicative fuel trim too lean.
I got secondary air injection trouble codes this morning, and sure enough the hose was cracked near both valves. This is at about 80k miles. It seems that the hose breaking is a question of "when" not "if", so if your car has it, you may as well replace it.
06-24-2004, 09:16 AM
#3
Mine were P1411 and P1423, others possible...
The bulletin also lists P0300, P0411, and P1128 as commonly associated with broken vacuum hoses. US market cars before 2000 did not have this vacuum hose, or even the secondary air injection system it controls.
06-24-2004, 11:36 AM
#5
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This is related to a very common problem with 2000+ A8s
. . . when the vacuum hose gets loose. See PaulW's writeup on airbil's car here: <a href="https://forums.audiworld.com/a8/msgs/19663.phtml">clickity-click</a>
Mine was loose but not cracked- an easy fix. Is this the same hose you're talking about?
<img src="http://www.audipages.com/Tech_Articles/enginemechanical/ai3.JPG">
Mine was loose but not cracked- an easy fix. Is this the same hose you're talking about?
<img src="http://www.audipages.com/Tech_Articles/enginemechanical/ai3.JPG">
06-24-2004, 01:35 PM
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Why is the braided cloth cover needed over the rubber hose? For insulation?
I'm replacing the same hoses on my Passat with just plain rubber hoses. Those stupid hoses are cracking in multiple places. And yes, I'm getting the stupid CEL's all the time.
