P1680 SES / REP lights on

[Hollywood260]

So, last night around 7:30 I was sitting in line at McDonalds after my sons baseball game. Its was about 85 outside and I had the air on in the truck. We had been sitting in line for about 15 minutes when all the sudden the truck lunges alittle, the SES/REP light kick on and then disappear....That was strange.....then about 2 minutes later it does it again and this time it goes fully into SES/REP and the lights stay on. I was sitting still each time!!! So, I happen to have one of those ELM 327 plugged into my ODB...so once it happened I pulled up the code and got P1680, so I reset it last night in hopes that I can figure out or narrow it down to certain things or instances. I've been scouring the forums here and abroad for an answer.......what I have come up with is a few things. APP Sensor is going out. Throttle body sensor is going out. PCM is going out or needs reprogrammed. And I even found something on this forum that states it could be the Clutch fan as its on the same 5v reference signal as the APP and throttle sensor. Has anyone had this issue before. A part of me is leaning towards the Clutch fan because I was sitting in traffic for extended periods of time with the AC on and I'm sure the Clutch fan was kicking on and off. Any help would be appreciated. I'm gonna try to mimick the issue today at lunch.

 

[The_Roadie]

Sorry about the problem. There has been a lot of discussion about it in all the usual places, and there was a trailvoy thread that you've probably already read: http://forums.trailvoy.com/showthread.php?t=43842

Fan clutches don't just "go bad" from being used. If the issue is a wiring problem on the shared 5V reference circuit, it's possible to be a fan clutch internal fault, an accel pedal fault, or in the throttle body itself. Or possibly other circuits that use the 5V reference. Or the harness going from the PCM to any of those things.

I would put a meter on the 5V reference wire going to any of those items, and wiggle the harnesses around and see if the 5V reading ever takes a dip. Otherwise it's time to start shotgunning, and that's never a satisfying process unless you're in a huge time crunch and not so much a limited budget.

 

[Hollywood260]

Even when its sitting still you think it lost the 5v reference? I can see while I am moving, truck is vibrating more.....I tried my whole lunch hour to reproduce this code. I turned the air on max and sat in one spot for 20 minutes and it ran just fine. Going to be hard to diagnose if it doesn't want to keep happening. But in the mean time, I'll check the 5v reference at those items and see what happens. Otherwise, I'm going to wait for it to happen again and see what the circumstances were.

 

[The_Roadie]

A wire with nicked insulation by going over a piece of sharp sheet metal might only fail intermittently, and be a bear to locate unless you catch it in the act with the means to measure the voltage.

 

[yodaddy4200]

I had this code six days after I bought my TB. I took it back to the dealer and had a nice chat with the head cheese. Long story short I got pissed and absolutely refused to pay the $900 they wanted.

They ended up taking care of it free of charge. It didn't take them long to fix... They didn't have my rig anymore than a normal appointment. .. They never actually said what they fixed.


I hate going to the stealership but... Some times that $80 diagnostic is cheaper in the end. Good luck!

 

[bobdec]

There is a service bulletin for some 04's, a code fix, could ask a dealer if it applies to your VIN. . #04-06-04-038 http://www.chevytruckworld.com/ew/forums/topic.asp?id=143987

 

[KNBlazer]

'04 TB EXT 4.2

I've had that code, along with P0606 for amost 4 or 5 years, haven't dealt with it as the truck is still running, therefore most likely needing a PCM FLASH.... in my case the codes pop up individually and or sometimes at the same time, but it's random, and typically after driving and coming to a stop....