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-   -   "Pending" P030X codes, occasional engine misfire (https://xoutpost.com/bmw-sav-forums/x5-e53-forum/101938-pending-p030x-codes-occasional-engine-misfire.html)

Rookie48 12-23-2015 02:44 PM

Sorry about that, edited signature...

Rookie48 12-24-2015 11:36 AM

Pulled all connectors to the DME and reset. No sign of oil, water, or coolant intrusion on the pins. Will be taking a long trip this afternoon and will log and see if resetting the pins has had any effect. After resetting the pins, the truck started and ran fine.

Thanks for the support guys! Happy Holidays!

Rookie48 12-27-2015 07:17 PM

More data in the dropbox file below... no limp mode (fuel status "8") encountered, but still throwing misfire codes on all cylinders, no other codes.


One thing I keep noticing, but don't know if it is normal or not is the wide voltage gap at times between the #1 O2 sensor on bank and #1 O2 sensor on bank 2. At times one bank is way lean and the other is way rich. The second O2 sensors seems to be very consistent...

Also - I assume the data "drops" ("0" values) or lack of change in value over several seconds is simply the logger trying to record data faster than the ECU can provide it.

Thanks in advance for any data analysis here!

jfoj 12-28-2015 09:50 AM


The most recent Log that you posted looks pretty good overall.

Do not be worried about the differences you are seeing in the Pre-Cat O2 sensors. This is likely due to the polling sequence and the slower response of the cheaper/slower interface.

Also the O2 sensors dropping to 0 Volts is typically during Decel with Fuel Cut Off, notice the Fuel System Status is at 4 during these time windows.

The only thing I am really seeing that may be something to watch for is the engine coolant temperature may be slightly lower than expected. Typically the M54 should run pretty consistently at 96C except under heavy load or higher RPM when the thermostat heater is commanded on.

But without knowing more details on how long the engine had been running, what the ambient temps were and if it was raining hard at the time it is a bit tricky to know if the thermostat is slightly soft. I also do not expect the engine temperature concern to factor into the overall problem you were having.

I still need to look over the 3 earlier Logs you posted a bit closer, still trying to catch up after the holidays.

Rookie48 12-28-2015 10:38 AM


Thanks for the quick glance at the logs. These were taken at highway speeds, after the truck had been running at least 1.5 hours on the highway, no rain, ambient temp was between 8 C and 9 C.

I have another log to post from this mornings drive into work - entered limp mode (at 9:00 - fuel status goes to "8", no SES light, restarted truck on the fly) and the SES light came on at 9:05.


I color-coded the timeslice where the limp mode happened...

jfoj 12-29-2015 11:26 AM


I am somewhat at a loss for the moment, nothing really standing out. There is an obvious Lean condition, but what came first the chicken or the egg??

So is the Lean condition a true Lean condition or is this due to Misfire with Fuel Cut off and is one or more cylinders pumping a lot of air/oxygen into the exhaust stream??

Shooting from the hip here, what is the status of the fuel pump relay? If it is original, I would replace it. Not 100% if the E53 horn and fuel pump relay are the same, if they are, swap them and see what happens.

I am tied up the rest of the day, will think about this and look over again in the next few days.

Rookie48 12-29-2015 04:30 PM


Swapped the relays a week or so ago, actually replaced the fuel pump relay with a brand new relay today. No change.

Also replaced the idle control valve, no change.

Removed and bench-tested the secondary air valve, it is working properly and had little to no carbon build-up.

Connected a fuel pressure gauge, secured it to the windshield, took it out for a test drive. Pressure never bobbled or moved off of 45 psi.

Drove home from the shop and again it threw misfire codes (all cylinders) and entered limp mode twice on the highway (above 75 MPH), and unusually it didi it in first gear going down a short hill into my driveway.

:dunno: at my wits end on this one.

upallnight 12-29-2015 05:09 PM

Have you ever done a compression test on all the cylinders? A miss to the DME is a cylinder that is not producing as much power as the other cylinders. Also when you replaced the MAF was it with a siemens or some cheap piece of crap?

Rookie48 12-29-2015 05:49 PM

Yes - performed a compression test two months ago (when issue started). All cylinders were within 5% of each other (~160 psi I believe was the norm). I replaced the MAF with a used OEM unit out of another E53 3.0i that was known to have no issue. I did not replace it with a brand new unit in trying to figure this issue out.

Just FYI - this truck is throwing misfire codes (P0300 through P0306) for all cylinders at the same time. No other codes are thrown.

jfoj 12-30-2015 01:38 PM


You have the M54 I6 engine as I recall.

I believe the fuel pressure should be Fuel pressure 3.5 +/- 0.2 bar or 50.76 +/- 2.9 PSI? Although 45 PSI is not far off, I would be double checking this along with your gauge.

How steep is the hill you are dealing with at the house?

I will need to read back over everything again in more detail as I have many vehicles in my head that I am dealing with.

Fuel pump was replaced? If so, what brand & where purchased?

I think the Fuel System Status changing to 8 here is the key, but the question is why. This usually occurs when the O2 sensor output does not toggle back and forth and follow the engine fuel management changes. I am starting to think there is possibly some Lean/fuel starvation problem here??

I understand you say the fuel pressure gauge did not move, but often the gauges do not connect properly. Did you see a quick drop in pressure when you shut the vehicle off?

Post any Freeze Frame data you get from both the driveway and cruising if you can get it.

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