U0101 code. Won't start.
Thread Starter
Senior Member
Joined: Jun 2012
Posts: 409
Likes: 22
2008 GL320CDI (310k) & 2017 GLS450 (160k)
U0101 code. Won't start.
After towing a trailer on a really warm day engine would crank but not start until temperature went down. Code U0101, no communication with transmission module. Later that day it would start and was fine for couple of days. But when I hooked up the trailer again, engine died after 30 miles of driving with the same trouble code. It will not start again. Do I need to get my transmission module control replaced/repaired? Did anyone experience this issue before? Last time transmission fluid was replaced at 140k miles.
MBWorld Fanatic!
Joined: Jan 2010
Posts: 3,105
Likes: 782
NGL450 w/EORP, S550
I’ve never had it to where the car wouldn’t start - it would go to limp mode locked in 2nd gear,
it’s possible that you dislodged or created so much grit that the vehicle speed sensor connectors in the valve body are now blocked. This is a typical failure mode and will require a dealer to reprogram the valve body to the new vss. There are also third parties out there that do this.
but first - have the car read out on DAS to confirm the specific error. U0101 is a very generic OBd code.
it’s possible that you dislodged or created so much grit that the vehicle speed sensor connectors in the valve body are now blocked. This is a typical failure mode and will require a dealer to reprogram the valve body to the new vss. There are also third parties out there that do this.
but first - have the car read out on DAS to confirm the specific error. U0101 is a very generic OBd code.
Thread Starter
Senior Member
Joined: Jun 2012
Posts: 409
Likes: 22
2008 GL320CDI (310k) & 2017 GLS450 (160k)
You are correct. I got my DAS working again and the error code is 0513. No communication with a transfer case module. Now I just have to find where its located.
Member
Joined: Dec 2018
Posts: 247
Likes: 59
From: Lawrence, Kansas
GL320
In DAS, go in to both the CDI4 and transmission and post here what the codes *AND* events show for both modules. Also post a screen shot of the control module version info (very top selection) for the transmission.
When it didnt start, did the electric fan begin to run at full speed? U101 is the early sign of a failing NT15/3 transmission control module (not the speed sensors). Please also ensure the connector at the transmission is fully seated.
Thread Starter
Senior Member
Joined: Jun 2012
Posts: 409
Likes: 22
2008 GL320CDI (310k) & 2017 GLS450 (160k)
I did check the transmission connector, it looks good. Fan does not run when I try to start it. Transmission has no fault codes but has one stored event: "0513 The CAN signal for start enable sent to the drive authorization system by transmission control is missing or invalid." This sounds like the issue I'm having, something is preventing engine to fire up. It does crank.
Thread Starter
Senior Member
Joined: Jun 2012
Posts: 409
Likes: 22
2008 GL320CDI (310k) & 2017 GLS450 (160k)
I also don't hear the fuel pressurizing when I turn the key. I'm sure that is why CDI4 is complaining about low fuel pressure. I should check for fuel delivery. Maybe the trouble codes are little misleading. It seems like immobilizer won't let the engine start. Does anyone have any other suggestions?
Trending Topics
Thread Starter
Senior Member
Joined: Jun 2012
Posts: 409
Likes: 22
2008 GL320CDI (310k) & 2017 GLS450 (160k)
I checked the fuse and relay for the fuel pump, all good. Plug to the unit gets power. When I apply power directly to the pump, nothing happens. I think that is my issue.
MB World Stories
The Best of Mercedes & AMG
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Verdad Gallardo
8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine
Verdad Gallardo
Flawlessly Restored Mercedes 190E Evo II Heads to Auction
Verdad Gallardo
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know
Verdad Gallardo
Mercedes EQS Gets A Major Update: Everything You Need to Know
Verdad Gallardo
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve
Verdad Gallardo
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping
Verdad Gallardo
10 Most Reliable Mercedes-Benz Models You Can Buy Used
Verdad Gallardo
Mercedes Teases Updated EQS With Steer-By-Wire and a Yoke
Verdad Gallardo
Thread Starter
Senior Member
Joined: Jun 2012
Posts: 409
Likes: 22
2008 GL320CDI (310k) & 2017 GLS450 (160k)
Just wanted to post a quick update and solution to this problem. New fuel pump fixed the issue. I was suspecting it was fuel related from the start but I went after CEL codes instead. Don't be like me and do basic troubleshooting first, make sure that you have air, "spark", and fuel. I still don't know why I had those trouble codes.
PS. Fuel pump was running and making little noise but no fuel was coming out, when I tested it.
PS. Fuel pump was running and making little noise but no fuel was coming out, when I tested it.
