2021 GLB 250 M260 - P0304 Recurring after Injector/Coil/Plug installed
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Mercedes GLB 250 2021 4Matic
2021 GLB 250 M260 - P0304 Recurring after Injector/Coil/Plug installed
Hi everyone,
I’m looking for some insight on a recurring P0304 (Cylinder 4 Misfire) on my 2021 GLB 250 4Matic (82k miles).
Background:
The car recently started misfiring on Cylinder 4.
What I’ve replaced so far:
I am getting a recurring P0304 and a "System Too Rich" tendency. After clearing codes, the car runs smooth for about 30 minutes, but after a hot restart, the CEL comes back within a minute from off state then start once again
Live Data at Idle (Fully Warmed Up):
I suspect the issue is that I have not coded the new Bosch injector. I bought a ThinkDiag, but unfortunately, the "Injector Coding" function is not accessible/supported for my specific 2021 model year in the app.
My Questions:
Thanks in advance!
I’m looking for some insight on a recurring P0304 (Cylinder 4 Misfire) on my 2021 GLB 250 4Matic (82k miles).
Background:
The car recently started misfiring on Cylinder 4.
What I’ve replaced so far:
- 4 brand new OEM Spark Plugs
- New OEM Ignition Coil for Cylinder 4
- New Bosch Fuel Injector for Cylinder 4 (purchased as Bosch aftermarket, not MB-branded).
I am getting a recurring P0304 and a "System Too Rich" tendency. After clearing codes, the car runs smooth for about 30 minutes, but after a hot restart, the CEL comes back within a minute from off state then start once again
Live Data at Idle (Fully Warmed Up):
- RPM: 700 (Steady)
- MAP: 32 kPa
- O2S11: 0.000 mA
- STFT1: -3.9%
- LTFT1: -14.1%
- EQ_RAT11: 1.011
I suspect the issue is that I have not coded the new Bosch injector. I bought a ThinkDiag, but unfortunately, the "Injector Coding" function is not accessible/supported for my specific 2021 model year in the app.
My Questions:
- Given that my MAP is 32 kPa at idling after ran 30 mins, can I safely rule out a burned valve? (I’m worried because of the P0304, but the vacuum seems too good for a mechanical failure).
- Since I can't access the coding menu, will the ECU eventually "self-learn" the new Bosch injector’s flow rate if I keep driving, or is manual IMA coding mandatory on the M260 engine to clear the P0304 for good?
- Has anyone had luck coding a 2021 GLB using a tool other than Xentry?
Thanks in advance!
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Joined: Sep 2013
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2021 GLB250 FWD, 2023 GLA250 FWD, 2013 C250, 2015 GLK350, 2005 ML350SE, 2003 E320
A quick comment of which you may already be aware:
2020-2021 M260 engines were showing P030x yy with the faulty head/valve train issue. Maybe you could do a compression test to rule this out. If your scanner can provide the yy part of the DTC, P0304 85 would be associated with this failure.
That’s the only DTC my 2021 showed and it ran fine, but the CEL was on and I did notice a drop in fuel mileage.
2020-2021 M260 engines were showing P030x yy with the faulty head/valve train issue. Maybe you could do a compression test to rule this out. If your scanner can provide the yy part of the DTC, P0304 85 would be associated with this failure.
That’s the only DTC my 2021 showed and it ran fine, but the CEL was on and I did notice a drop in fuel mileage.
