8 speed shifting strangely, followed by check engine and a P0651 code

MDSilveradoGuy · May 21, 2019

I crossed the 3,000 mile mark yesterday (yeesh, I’ve had it a month). This morning on the highway, went to accelerate and my trans bucked hard a couple of times (felt like a manual when it’s in too high of a gear), then downshifted. The rest of the trip it seemed eager to downshift - it seemed like any time you would breathe on the pedal it would drop a gear or two. When I went to back into my spot here at work the Check Engine light came on with a P0651 code. I’m dropping it off tonight.

I just hope whatever it is it’s a quick fix. It’s the beginning of boating season and I need my truck.

Edited May 21, 2019 by MDSilveradoGuy

MDSilveradoGuy · May 21, 2019

And it gets better. Came out to leave work, tried to start it - it cranked a few times, stopped, reduced power and service ESC messages and now it just clicks.

Called Onstar, tow truck is on the way to get it and my partner is coming to get me... nothing like a 2 hour round trip drive.

Edited May 21, 2019 by MDSilveradoGuy

MDSilveradoGuy · May 21, 2019

It’s popping a p0651, p0335, p057c and p16e4 code. So basically 2 low voltage, 1 sensor open and 1 crankshaft sensor. It makes me wonder if I have a bad battery or alternator. I have noticed that the battery voltage fluctuates more in this than anything else I have owned as well as the auto start is not able to make it through most traffic lights without restarting the engine.

JimCost2014 · May 21, 2019

9 minutes ago, MDSilveradoGuy said:

It’s popping a p0651, p0335, p057c and p16e4 code. So basically 2 low voltage, 1 sensor open and 1 crankshaft sensor. It makes me wonder if I have a bad battery or alternator. I have noticed that the battery voltage fluctuates more in this than anything else I have owned as well as the auto start is not able to make it through most traffic lights without restarting the engine.

From experience, the crankshaft sensor will disable the engine completely, so it will do no further damage.

Unfortunately, that code could be as easy as the plug on the sensor has come loose, or multiple things inside the engine have failed.

Good luck.

Edited May 21, 2019 by JimCost2014

MDSilveradoGuy · May 22, 2019

1 hour ago, JimCost2014 said:

From experience, the crankshaft sensor will disable the engine completely, so it will do no further damage.

Unfortunately, that code could be as easy as the plug on the sensor has come loose, or multiple things inside the engine have failed.

Good luck.

It’s many other codes now. I’m thinking electrical since it is throwing low voltage codes all over. Apparently there is a TSB out for the engine harness on the 2.7s so it could be that too.

ShamrockShooter · May 22, 2019

Well on the bright side it didn't happen while you were towing your boat.

Sent from my Pixel 2 using Tapatalk

AMPRG · May 22, 2019

How does the voltage look like in the cluster? I heard that sometimes, aftermarket and cheap USB chargers, or cigarette lighter plug-in like the dash cams, cause problems overnight, due to draining the battery, and electromagnetic interferences.

Edited May 22, 2019 by AMPRG

MDSilveradoGuy · May 22, 2019

10 hours ago, AMPRG said:

How does the voltage look like in the cluster? I heard that sometimes, aftermarket and cheap USB chargers, or cigarette lighter plug-in like the dash cams, cause problems overnight, due to draining the battery, and electromagnetic interferences.

Here’s the last one of it running. Fairly typical for it and lower than I’d expect but it does fluctuate a bit.

Nothing aftermarket plugged in.

AMPRG · May 22, 2019

15 minutes ago, MDSilveradoGuy said:

Here’s the last one of it running. Fairly typical for it and lower than I’d expect but it does fluctuate a bit.

Nothing aftermarket plugged in.

Then my theory is out the window ?

JimCost2014 · May 22, 2019

15 hours ago, MDSilveradoGuy said:

It’s many other codes now. I’m thinking electrical since it is throwing low voltage codes all over. Apparently there is a TSB out for the engine harness on the 2.7s so it could be that too.

Bad news that this is happening,

But, what did you think of the 2.7 when it was running correctly.

Don't think I have seen anyone post their thoughts on the new engine on the site yet (I could be wrong).

MDSilveradoGuy · May 22, 2019

I just got a call from the dealer. Apparently there is a fault in an underhood fuse block, and another one will arrive to be installed tomorrow "and they will test from there".

I really hope this is the fix... the boat beckons.

Regarding the 2.7 - I absolutely love it. There is a "2.7 owners fan club" thread on here, but not much else. It doesn't sound like a V8 but makes a nice low grumble as it goes about its business, with a lot of turbo whistle as well.

It pulls like a freight train when I have the boat behind it. It redlines at 5,700 RPM - I have yet to see mine go above about 5,000 - but it doesn't need to and isn't happy being wound out.

I got tired of waiting for the Duramax - I am glad I didn't (so far... although these issues with my truck are not engine related)

econometrics · May 22, 2019

4 hours ago, JimCost2014 said:

Don't think I have seen anyone post their thoughts on the new engine on the site yet (I could be wrong).

FYI:

JimCost2014 · May 23, 2019

4 hours ago, econometrics said:

FYI:

Thank you.

MDSilveradoGuy · May 24, 2019

This whole thing has just gotten ridiculous. This is long but worth it.

There is a TSB out for the wiring harness on the 2.7 rubbing on the engine cam cover, which rubs through the insulation and shorts out some wires causing drivability issues. The fix for that is to repair those wires and rewrap the wiring harness (I have the TSB), which to me is unacceptable - and I will be taking this up with GM. The dealer performed the fix but it still wouldn't start. They then discovered that the 400A main fuse was blown. Replaced that, the truck fired up, and they called me to come get it.

I rolled over there last night in the miserable Malibu they gave me as a loaner (1.5L, 6 speed, something wrong with the trans where it wouldn't kick down, upshifted at 5K RPM at WOT, nearly got me flattened in DC traffic). Porter pulls my truck around, I see him say something to another service writer and she was looking in it. They smile and hand me the keys, I get in my truck and fire it up to a Christmas tree dashboard and ton of messages on the DIC. I went ballistic at this point, another service writer comes over to take a look at it, they take me to get another rental (a neon blue over white cloth Chrysler 300 which they just got back after someone put it up on blocks, stole the wheels and busted the windows out of it... not being a choosing beggar but cripes I feel stupid driving the thing). We had a con call this morning to discuss this whole ordeal and my need to tow my boat this weekend for a trip, and I can't do that with a 300. They told me my truck was fine this morning with no errors, just historical codes which they cleared, and they were going to keep it and drive throughout the day to try to reproduce.

The foreman and service manager called me earlier from it while on a test drive to let me know that it was ready to go. While on the phone, it decided to turn into a Christmas tree and light the DIC up with error messages again. They told me they would call me when they knew what was going on with it. They called me about an hour ago, and the first thing out of his mouth is "How much does your boat weigh?", to which I said "It sounds like I am not getting a truck back this weekend". Apparently now the TCM isn't communicating with anything and they have escalated this with GM. They are putting me into a Grand Cherokee with the tow package in a few minutes when I head that way.

No one knows why that 400A fuse blew. My fear is that some major short has happened and God knows what it took out in the process. I'm not trying to let it ruin my weekend... I just want my truck back.

Edited May 24, 2019 by MDSilveradoGuy