Slight hiccup at limp mode

GT456! · Post by **GT456!** » Sat May 30, 2026 8:45 pm

While finishing up the second half/ leg of the 500 mile journey...the X3 went into limp mode, started to idle crappy and the car crused to 15 mph. Outside temps mild. No check engine light. No response from the gas pedal. Pulled over, stopped and then turned off the engine. Immediately turned the engine on and got back on the freeway... back to normal for the next 2hours. This M54 never has given me any problems in the recent past...I just changed out the fuel pump in February.
Car is 22 years old...
220k on the clock.
When I started out this morning before the drive I changed the air box filter. Could this cause the hiccup?

X5Sport · Post by **X5Sport** » Sat May 30, 2026 9:12 pm

Any error codes showing?

I can’t see an air filter causing an issue unless you disturbed some wiring. Given it restarted fine and drove on without a repeat is more puzzling.

GT456! · Post by **GT456!** » Sat May 30, 2026 9:25 pm

X5Sport wrote: Sat May 30, 2026 9:12 pm Any error codes showing?

I can’t see an air filter causing an issue unless you disturbed some wiring. Given it restarted fine and drove on without a repeat is more puzzling.

My sentiment exactly

!
Thought I'd run it past you...I'll monitor from here on. "Unless you disturbed some wiring"
I did disconnect the maf sensor but of course I reconnected it.
Thanks for the response

X5Sport · Post by **X5Sport** » Sun May 31, 2026 4:27 pm

MAF would be a likely candidate as no air means no acceleration. Might be worth having a look at the pins in the connector to see if they are clean.

GT456! · Post by **GT456!** » Sat Jun 13, 2026 5:10 pm

Cleaned/sprayed out the secondary air pump also mistakenly known as the EGR valve these petrol M54 don't really have a valve. This may just be the answer. But the hiccup hasn't shown up since

GT456! · Post by **GT456!** » Mon Jun 29, 2026 9:18 am

IMG_20260628_211314.jpg

I'm getting codes P0123 (Circuit High) and P0222 (Circuit Low) it is mathematically and electrically impossible for the sensor to be reading both maximum voltage and zero voltage simultaneously.
I'm told...
The engine computer (ECU) has completely lost its ground connection or its 5-volt reference signal loop to the throttle body assembly.
Resulting in...
The Most Likely Culprits (Ranked)
*Broken Main Ground Wire (~ 60% of cases)
*Melted or Chafed Wiring Harness (~ 30% of cases)
*Internal Sensor Short (~ 10% of cases)

What I'm going to do to remedy this?

IMG_20260628_211225.jpg

I'm going to transplant the m54 main wire harness...Ive got one on hand from a donor X3 from the boneyard.

GT456! · Post by **GT456!** » Mon Jun 29, 2026 3:21 pm

Ever wonder what's inside the harness housing...

XSeries-forum

XSeries-forum