Blinking CEL/MIL, rough idle, 16684 engine misfire, 16685 cyclinder 1 misfire, ICU failure
01-13-2006, 09:12 AM
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Blinking CEL/MIL, rough idle, 16684 engine misfire, 16685 cyclinder 1 misfire, ICU failure
After what could potentially be a disastrous and expensive situation, I owe it to all of you at AW to post this follow up to a very common problem that no one has really posted a follow up on.
Having your car break down on you (especially in California) is a very stressful situation and I thank you all at AW for posting your knowledge to reduce some of the helplessness one feels when encountered with such a situation.
On a wet evening, I was driving my 99.5 A4 1.8TQ (mileage = 93K) on the freeway and after about over an hour of speeds over 80mph, I reached the city when my car started this horrible shuddering and the check engine light started blinking. I was only about 1 mile from home so I cautiously limped the car home. I had an job interview in 2 days and I needed my car to get to it, so my stress level was high.
The symptoms of my car were:
1) blinking CEL (check engine light) aka MIL (malfunctioning indicator light)
2) high pitched whirring sound from the engine
3) rough idle (RPMS stayed at around 2K and car was shaking violently)
4) pulsing exhaust
5) extreme power loss
The next day I pulled the codes with a VAG-com and got 16684 engine misfire and 16685 cylinder 1 misfire.
Good site for DTC search:
http://www.s4biturbo.com/dtc_search.cgi
I read the posts on AW and narrowed the causes to one or a combination of three things failing:
1) ICU/ICM/POS/N122
2) Spark plugs
3) Coil Pack
I checked the spark plugs and they looked good. I checked the coil packs via "musical coil packs" and all 4 were good.
Here is a good link on interchanging the coil packs from scott by BOSTON:
http://www.quattro123.com/A4MisfireCoilPacks.htm
This is the definitive procedure for testing the ICU/ICM/POS/N122 by ArandA4:
https://forums.audiworld.com/a4/msgs/1594531.phtml
I didn't have a multimeter so I could not test the ICU, but by process of elimination and from all the other similar posts, I was pretty sure that it was the culprit. The only thing I was unsure of was that the common symptom from the posts for the ICU failure was a misfire on cylinder 2, and I was getting a misfire on cylinder 1. Not knowing where else to go, I purchased a replacement ICU p/n 4D0 905 351 from AutohausAZ.com for $103.xx
http://www.autohausaz.com/index.html
With overnight shipping for $25, the total cost was under $130. I received the part the next day, swapped it out in less than 5 minutes and with laptop and fingers crossed I fired the car up, cleared the codes and bingo! Problem solved. The CEL stayed off, the car returned to a normal idle and I made my interview that afternoon. Don't know if I got the job, but the most important thing, I have my car back.
\
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Having your car break down on you (especially in California) is a very stressful situation and I thank you all at AW for posting your knowledge to reduce some of the helplessness one feels when encountered with such a situation.
On a wet evening, I was driving my 99.5 A4 1.8TQ (mileage = 93K) on the freeway and after about over an hour of speeds over 80mph, I reached the city when my car started this horrible shuddering and the check engine light started blinking. I was only about 1 mile from home so I cautiously limped the car home. I had an job interview in 2 days and I needed my car to get to it, so my stress level was high.
The symptoms of my car were:
1) blinking CEL (check engine light) aka MIL (malfunctioning indicator light)
2) high pitched whirring sound from the engine
3) rough idle (RPMS stayed at around 2K and car was shaking violently)
4) pulsing exhaust
5) extreme power loss
The next day I pulled the codes with a VAG-com and got 16684 engine misfire and 16685 cylinder 1 misfire.
Good site for DTC search:
http://www.s4biturbo.com/dtc_search.cgi
I read the posts on AW and narrowed the causes to one or a combination of three things failing:
1) ICU/ICM/POS/N122
2) Spark plugs
3) Coil Pack
I checked the spark plugs and they looked good. I checked the coil packs via "musical coil packs" and all 4 were good.
Here is a good link on interchanging the coil packs from scott by BOSTON:
http://www.quattro123.com/A4MisfireCoilPacks.htm
This is the definitive procedure for testing the ICU/ICM/POS/N122 by ArandA4:
https://forums.audiworld.com/a4/msgs/1594531.phtml
I didn't have a multimeter so I could not test the ICU, but by process of elimination and from all the other similar posts, I was pretty sure that it was the culprit. The only thing I was unsure of was that the common symptom from the posts for the ICU failure was a misfire on cylinder 2, and I was getting a misfire on cylinder 1. Not knowing where else to go, I purchased a replacement ICU p/n 4D0 905 351 from AutohausAZ.com for $103.xx
http://www.autohausaz.com/index.html
With overnight shipping for $25, the total cost was under $130. I received the part the next day, swapped it out in less than 5 minutes and with laptop and fingers crossed I fired the car up, cleared the codes and bingo! Problem solved. The CEL stayed off, the car returned to a normal idle and I made my interview that afternoon. Don't know if I got the job, but the most important thing, I have my car back.
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