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Shut off while driving, OBD2 connection failure

Tiny
BINH TRAN2
  • MEMBER
  • 1997 MERCEDES BENZ C280
  • 2.8L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 160,000 MILES
Hi, wife was driving the car. Suddenly engine stop, coasting to a stop. Try to restart, the starter has no cranking. All electrical works, gas is full, the battery is 2 years old. The car has been parked for a month in the driveway. I bought an ODB2 try to connect, device response "failure to connect" retry. Remove, reconnect, the same result. Tried OBD2 on an Odyssey van and it reads codes fine. This means the OBD2 is fine. What could be wrong with the C280? I am thinking: ECM failure so OBD cannot read. Could that cause the fuel pump and starter circuit to fail too? Thank you for your help. I thought I could read the code to see what system failed.
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Friday, May 14th, 2021 AT 7:21 PM

11 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

Does the scan tool power up when connected? If it doesn't, check pin 16 for power, It should be present at all times. Also, pin 4 should be the ground, so confirm there is continuity to ground at that pin.

If there is no power, check fuse 1 in the passenger side fuse box. In addition to checking the fuse, confirm there is power to and from it. Here is a link you may find helpful:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

I attached the wiring schematics for the entire engine control system. I had to cut the pics in half, but I did overlap them so you can follow from one to the next. In the first pic below, I highlighted the DLC power supply and which fuse powers it.

Let me know what you find or if you have other questions.

Take care,

Joe
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Sunday, May 16th, 2021 AT 7:28 PM
Tiny
BINH TRAN2
  • MEMBER
  • 8 POSTS
Thanks Joe, the obd2 has power when plug in and appears to attempt to connect, screen show black connecting bar moving then after 15 seconds failure message appears. I will check and update.
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Sunday, May 16th, 2021 AT 8:10 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

Disconnect the battery, locate a disconnect the ECU behind the engine. Check the pin connectors for corrosion or damage. Specifically, check pin 39. See pic below.

Let me know what you find.

Joe
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Monday, May 17th, 2021 AT 8:05 PM
Tiny
BINH TRAN2
  • MEMBER
  • 8 POSTS
Hi Joe, will do and will update as soon as rain stops in Seattle!
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Monday, May 17th, 2021 AT 8:31 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
No problem. I'll watch for your reply. I'm on the opposite end of the country. LOL The next 7 days are dry! I can't believe it.

Take care,

Joe
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Monday, May 17th, 2021 AT 9:24 PM
Tiny
BINH TRAN2
  • MEMBER
  • 8 POSTS
Hi Joe, I disconnect battery, pulled the ECU and ABS module and inspect them. All terminals and connectors/wires looks brand new. Pulled each and every one fuses in engine compartment and trunk, they are all good. Reconnect OBD 2 and still fail to connect. Took picture and video so you can see.
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Tuesday, May 18th, 2021 AT 7:41 PM
Tiny
BINH TRAN2
  • MEMBER
  • 8 POSTS
OBD2 connection failure.
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Tuesday, May 18th, 2021 AT 7:41 PM
Tiny
BINH TRAN2
  • MEMBER
  • 8 POSTS
I am ordering an adapter for the 38 pins to OBD2 to see if any different. Next I plan to open lower engine guard and gently tap the starter to see if it wakes up. If not how do I test if turning the key send power to starter or not? Then the fuel pump is next if I get starter to crank. Any suggestions are appreciated.
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Tuesday, May 18th, 2021 AT 7:46 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

I attached two links. The first explains how to check the starter not working and the second is how to test fuel pressure.

https://www.2carpros.com/articles/starter-not-working-repair

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Let me know if that helps.

Joe
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Tuesday, May 18th, 2021 AT 8:09 PM
Tiny
BINH TRAN2
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Thank you, I will check the starter trigger wire next to see if there is power when key turns to crank position.
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Wednesday, May 19th, 2021 AT 1:10 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Sounds good. Let me know the results and we'll continue.

Take care,

Joe
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Wednesday, May 19th, 2021 AT 7:36 PM

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