Code P1602-002 - Power Supply to terminal 30 voltage too low

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Jack@European_Parts

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Well....something has changed for the worse on the Audi. Fuse #13 (located in left plenum just below windshield) powers many components such as Secondary Air Pump, Evaporative Purge Valve, both Fuel Metering Valves, both MAF's, etc. Earlier in this thread Jack stated that this fuse and related components need to be evaluated. All of the scans so far show that the Secondary Air Pump, and Evaporative Purge Valve, are shorted to ground - when I unplug these items the scan then shows an open circuit. I did measure the resistance of the Evap-Valve since its easy to get o...and it is within specs. - so I assume the "short" must be after this component. What is odd is that even thought the scans show these are shorted to ground, the fuse #13 does not blow. Well....all of that came to an end as of this morning as this fuse is now blowing at each start up. So the problem has escalated...maybe this will actually help me find the issue now. I will work on the Audi again tonight. Also...I still plan to contact the independent Garage today to consult with them about this....if I can't find the issue I'll have the Audi trucked to them.




Easy ..........now unplug each shared track until a lower AMP fuse doesn't blow and there you have it by isolation.

Then change that component or overlay the damaged wire harness......

No one needed to do that considering what you already accomplished.
 
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Okay...I unplugged both MAF Sensors, both HPFP Regulator Sensors, and the Evaporative Purge Valve....I did not pull the Relay for the Secondary Air Pump (forgot). I then put in a 10 amp fuse (Fuse S13 calls for a 15 amp). I started the Audi, it cranked a bit and then reluctantly fired up. I held the idle speed around 1200rpms for maybe a minute then I shut it off. I then pulled the fuse to see if it was blown - NOPE. I did this repeatedly for each component and eventually had everything plugged back in...and this time the fuse did not blow for some reason. In every case the EPC light came almost immediately. However when I had everything plugged back in except for the Evap Valve...it took a little bit longer for the EPC to come on. I guess there must be a problem with either the connectors and/or the wire harness for the components on the top of the motor. Perhaps I could just buy a new wire harness for this group of items?
 
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Just an update for those who may be interested. I took the Audi to our local imports specialists garage - they were highly recommended by the local VW dealer. So the Audi has been with the for 2 weeks now and they still do not know the issue. They are trying to find a voltage drop in the wire harness but haven't so far. They also mentioned a possible voltage spike from the alternator, causing the "system" to shut down? They are also considering the fuel rail pressure sensor (under the intake manifold) as a possible culprit. They are consulting with Audi-North America as well. This shop works on all the high end import brands so the Audi should be in capable hands. I'm not convinced though. I have stopped in and spoke with the shop manager and he really does seem to know his stuff. They have named the Audi "nightmare on elm street" because the issue seems to come and go. They said that neither they nor Audi have ever seen so many fault codes before.

There is a nice used Range Rover for sale locally and shamefully I stopped and took a look at it. It's a 2010 model that appears to be in great shape. But from what I've read the electronics on these vehicles are possibly even worse than the Audi, since Rover has had multiple owners in the past and all of the different technologies are mixed together.....BMW, Ford, and Rover. It sure was a nice driving vehicle.
 
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Yes I sure would be a glutton for punishment if I got a Range Rover. The engine was a new 5.0 liter from Jaguar and had a lot of horsepower and torque - I was surprised at how quickly it moved 3 tons of vehicle. Surfing the net reveals a lot of electrical glitches in Range Rovers, but from around 2007 to 2009 they seemed to get better, and then in 2010 a bunch of upgrades were incorporated - and you know how the quality is for an introductory year...pretty sketchy. I was most impressed with the ride quality - even with 20 inch wheels...bumps were almost imperceptible. And at highway speed it was very quiet in the cabin. The AC was other-worldly as it blew ice cold almost immediately. Everything inside was leather covered with contrasting piping - very classy. What amazed me was the center console touch screen, from the driver's view it showed various controls and functions, and AT THE SAME TIME from the passenger's view it showed videos and other entertainment....how do they do that? I can see why people spend $100k on these vehicles despite the issues.
 
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UPDATE 11-12-16: The problems are FIXED...!!!!

Just wanted to update everyone, after 5 weeks of sitting in the repair shop, the mechanics finally fixed the Q7. The main issue was the High Pressure Fuel Pump on driver's side cylinder head. The fuel pressure regulator was intermittently shorting out. When it shorted it dropped the voltage supplied to many other components, resulting in a zillion different fault codes. The pump was also mechanically bad internally. Once this was changed out the car ran great. Further diagnosis also discovered some small vacuum leaks in the plastic tube for the crankcase ventilation system, this tube connects both cylinder heads to the oil vapor separator. There were some tiny cracks in the tube, the shop repaired it and all is good. I will be getting a brand new tube in the near future. But I'm very happy to report the Audi is running smooth as glass now! Thank You for Jack and Uwe and all the gang for helping me through this ordeal....I really appreciate it.
 
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Jack@European_Parts

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Thank you for reporting back for the JPPSG.
Did they find a faulty cam or lifter to HPP too?
 
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Hi Jack....thankfully camshaft and lifter are fine, I was worried about those too. I think I'm going to buy another high pressure fuel pump for the other cylinder head and change that out....as a preventive measure, I'm sure it's only a matter of time before it becomes a problem. The Q7 is running great, the mechanic also commented on how smooth the engine is. I told him that I de-carboned the valves and intake system, and he agreed that would make a difference.
 
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