Engine Control Unit Failure After Injector Replacement

Hello,

In my 10-year-old A-Class (A170cdi), with approximately 110,000 km, the fuel tank was eventually replaced as a goodwill gesture. Unfortunately, the mechanics overlooked a foam pad inside the new tank, which completely dissolved when diesel was added. As a result, the car completely stopped working after just a few kilometers because all four injectors were completely clogged by this mixture.

After that, the fuel tank, fuel filter, and injectors were replaced, and the fuel lines were cleaned.

After I picked up my car, the engine made a loud noise at approximately 2500 RPM, and this noise was consistently reproducible. When I called the workshop, I was assured that everything was fine with the engine, as a test drive of over 30 km had been conducted and nothing unusual was heard.

After driving approximately 600 kilometers, the engine then only ran in a limited mode (restricted to a maximum of 3000 RPM and a top speed of 120 km/h). This occurred a few days after the engine had already been running quite unevenly, and I had already felt like it was about to stall.

So, I had my car towed directly to the repair shop.

During the inspection of the electronics, it was determined that both the crankshaft sensor and the camshaft sensor were defective. After replacing them, an additional error message appeared, indicating a faulty engine control unit.

My workshop doesn't see any connection between this issue and the injectors that were replaced/defective 600 km ago.

I would be very grateful for any information regarding whether the addition of injectors could affect the engine control unit.



Best regards,

Sure, here is the translation of the text from German to English:

"Elchi2000"

Hi,
Please provide the chassis number and engine number. Do you have the 66kW/90PS engine?
Sure, here is the translation of the text from German to English:

"vg" is an abbreviation for "very good". It is often used in online forums and chat rooms to express agreement or approval.
Herbert.

As a supplement:

Engine code: OM 668.940
Chassis number: WDB1680081Jxxxxxx

Best regards, Elchi2000.

Hi Elchi,
There is currently no causal relationship between the damaged injectors and any potential damage to the sensors for the crankshaft (CKP) or camshaft (CMP) position, or to the engine control unit (ECU). The failure of one component cannot trigger a defect in the other.
However, both sensors and the control unit (ECU) are connected by a wiring harness that is touched when the injectors are replaced. The wiring harness, starting from the ECU, has a mounting point at the fuel filter, then it continues to the fuel pumps, the sensors, and underneath the intake manifold to the injectors, etc.
You know how tightly everything is packed in there. I've already replaced the injectors on engine 942 (A170 CDI, manufactured in 2002), which is similar.
The question is whether the wiring harness was damaged during the assembly work to replace the injectors. At least, the fact that first the crankshaft and camshaft sensors and then the control unit failed makes me suspicious.
In my opinion, the wiring harness and all the connectors should be checked first.
If, despite everything, the workshop wants to install a new control unit (ECU), have them show you the error code from the old one (be present during the diagnostic scan), observe the replacement process, and have them demonstrate that the new one is error-free.
Regarding the previous repair - if that's what happened, they did a really thorough job. Shouldn't the pre-pump, the high-pressure pump, and the pressure regulator also have been replaced? Were the combustion chambers inspected with an endoscope?
Sure, here's the translation:

"vg" is an abbreviation for "very good." It is often used in online forums and social media to express approval or agreement.
Herbert.

Hello Herbert,

Thank you for all the tips. We will definitely check the wiring harness.
Have it checked again, even if the workshop probably already did.
We will find out if the control unit is actually defective when it is examined by the...
...has been returned for inspection or repair. We have it now.
submitted by myself.

You're also right about your statements regarding the exchange.
Fuel pumps, endoscopy, etc. That's what was stated, at least.
I did everything in the workshop.

Best regards,
Ambassador.