Hi all, I recently bought a 2007 e350 4matic with over 140K miles that was running fine for about a year before I got the check engine light with the following codes:- P0301, P0351, and P2006.

· I installed new spark plugs.
· Swapped ignition coils between cylinder 1 & 2.
· Cleared the codes and started the car.

Within a minute or two, I got P0301 and P0351 again. P2006 did not come back.

The car is rough on idle as well as when driving but not too bad.

Added 6 OZ of “Hi Performance Lucas upper cylinder lubricant with injector cleaners and fuel conditioners” to about half a tank of premium gas. Drove the car to empty and added 10 more OZ of Lucas with the new full tank of gas and drove some more miles with no change to the above.

I’m now thinking it is either the Control Unit, or the coil harness. So with my multimeter I got some readings but I could not make sense out of them. Hopping someone can suggest the next step to diagnose the issue at hand.

PIN 2 & PIN 3 on the ignition coil-coupling end for both cylinders 1 & 2 tested as a good ground with the key out of the ignition as they should. I cleared the codes between tests since starting the car triggered the codes every time.

On both cylinder 1 & cylinder 2 I checked the voltage between PIN 1 & PIN 4 as follows:

Cylinder 1

· Key is out of ignition it was -00.22 volts!
· Ignition is on position II (dash lights on) it was 10.6 volts!
· When car is running voltage climbed from 10.6 to 12.6 volts max! The Min was 12.5 volts!

Cylinder 2

· Key is out of ignition it was +00.00 volts.
· Ignition is on position II (dash lights on) it was 12.35 volts.
· When car is running voltage climbed from 12.35 to 13.5 volts max. The Min was 0.0 volts.

Questions:-

What does it mean to have a negative 0.22 volts between PIN 1 & PIN 4 with the ignition off?
If both cylinders 1 & 2 get their power from the same source, why is the voltage on cylinder 1 is too low?
Why is the minimum voltage on PIN 4 not dropping to zero?

I ordered the iCarsoft code scanner and hoping I can get more live data when I receive it, but not sure what test to select. Never used an advanced code reader with live streaming options.

Any suggestion on next logical test is kindly appreciated?

Tests update:-

1. Coil and sparks plug are good.
I took the sparks plug out of cylinder 1, inserted it at the end of the coil and grounded one end of it but got no spark on the sparks plug when starting the engine. I did the same for cylinder 2 and the got sparks on the sparks plug. Used the coil and sparks plug from cylinder 2, connected to cylinder 1 harness end but again no sparks.

2. Wiring from ECU to Coil is good.
I found the harness schematic and traced cylinder 1 ignition coil PIN 4 (signal pin) to the ECU coupler PIN 6 and got a solid continuity beep from my multimeter. ECU coupler discommoded from the ECU. PIN 1 have a steady 12.4v when engine is off. PIN 2 & 3 are grounded.

3. At that point, it looks like I have a bad ECU ignition drive IC or some other IC…
I set my multimeter to Hz and connected 12v to one end and the other end touching PIN 6 on the ECU harness back-end (cover of harness removed gently) … the Hz started at 9Hz for a 2 second then dropped to 0Hz. I did the same with PIN 8 (Cylinder 2 Coil signal) … it started with 0Hz for 2 to 3 seconds, then up to 8.9/Hz for a split second, then continued to go down steadily to rest at around 6Hz +/- 0.04Hz while the engine is running.

4. Code scanner tests.
Collected all possible live data that my new scanner can get (iCarsoft CR Pro) during a 10 minutes and 6 miles test drive and got lots of data that I have no idea why I do not have a spark in cylinder 1! I also collected some more codes such as P2004 about the broken leaver on my intake manifold actuator (the one in the middle). This might shed some light on the live data numbers but it the facts remain that I have no spark in cylinder 1, and the Hertz (Hz) value in test 3 above is pointing to a problem in the ECU.

• Attached excel file have all 65 frames of data from the test drive.
• Below are the OBD2 codes.

0629 1/4
State: Current
Misfiring(P0300)

0633 2/4
State: Current
Misfiring of cylinder 1: Damages TWC(P0301)

1015 3/4
State: Current
The control line to the ignition coil of cylinder 1 has an open circuit, (P0351)

0521 4/4
State: Current
Diagnosis of tumble flap 'Intake manifold': Short circuit to ground of sensor lines / Tumble flap shafts stick in the actuated position, (P2004)

Please give me your feedback if I’m on the right track suspecting a bad ECU before I go out and spend money on a used clone ECU or send mine for repair.

 

Attaching the wiring diagram used to test coil signals from ecu

 

any ECU experts out there????

 

The ECU was sent for repair, see attached image, and I have to confirm all grounds are good before reinstalling it.
Does anyone have pictures where I can find the main ground strap for the engine and other important ground points?
How can I confirm my alternator and battery are not shorted out? I have a good 12.6 volts on the battery and it goes up to 14.x once the car is started. Is that a good enough test to confirm they are both ok?

2007 E350 4Matic ECU M9.7 damage repair

 

I’m still getting a misfire code in cylinder 1 but it does not happen when the car is first started. It will run fine for 4 to 5 min then the check engine light will pop up and you feel the engine rough at ideal.

After I got the ECU repaired, I disconnected, cleaned and reconnected the 3 ground contact point in the engine compartment and totally replaced the main ground cable / ground strip under the car by the transmission with an OEM part from the dealer. I also cleaned the main battery terminals. (See pictures)

Note: The 07 4matic does not have an aux battery under the HVAC filter.

I also ran a compression test all 6 cylinders range around 170. Cyl 1 at 171 dry test and 181 wet test.

I recorded about 7 minutes of live data as soon as I started the car until I got the misfire occurred but not sure what it all means.

Before the check-engine-light, coil 1 had sparks, but not after. The ECU must have shut it down.

I can’t figure out what is causing the misfire and setting codes P0300, P0301, and P0351 !

Should I start replacing parts starting with a fuel injector for cylinder 1? Any suggestion ?

 

Were you able to solve this issue?

 

Yes it has been running fine since. See recommended fix from mrspencer10 below and I will try to upload some pictures when I get home.

https://mbworld.org/forums/members/4...spencer10.html

bought the coupler and pins from MB dealer for less than $20 if I remember correctly.

 

Sorry the link did not show the fix… in short the coupler that pulgs into the coil for cylinder 1 was bad or the pins inside were loss. I broke it to pieces, since I could not pull the wires out of it, cut the wires ends very close to the old pins, striped the wires and crimped the new pins with a mini crimp tool I got from Amazon. Pushed the pins into new coupler and the fix worked.