Hi all,

I replace the MAF sensor with a new Bosch unit, and also the air filter element, and I still get intermittent P0100 codes, I can reset the code and it will set again within 10 minutes of driving. I have cleared it about 5 times. Is there anything else in the intake system that could be causing it? Before I replaced the MAF sensor the code was always set, now it's intermittent. The performance improved after replacing it though.

Thanks,
Cameron
San Diego

Check voltage to the unit (voltage between pins 2-3) - should be normal 12-14.5 volts. If it's low, check fuse 29.

Air leaks bypassinig the MAF

was the "Bosch" MAF a complete unit or an insert?

P0 100 indicates NO return voltage from MAF, only a wiring issue or bad MAF will set that code.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

I had trouble with the wires going to the MAF's...

http://v12uberalles.com/MAF_rewire.htm

__________________
1995 S600, 1 of 618 (sold)

"Speed is just a question of money...how fast you wanna go?"

LONG LIVE THE W140!
Visit my Web Page at www.v12uberalles.com

I'll check the wiring tomorrow, but if there's a blown fuse or low voltage, wouldn't that be a hard code? This seems to set a hard code mostly when cold, then if you reset it, then it waits awhile to come on again.

Thanks,
Cameron
San Diego

It's either your mass flow sensor, the voltage from it (which is also dependent on the voltage to it), or the throttle position.
It measures the mass flow rate at a given throttle angle, and throws a fault if it's outside the range.
I guess you should check that your accelerator cable is correctly adjusted: it should rest against the idle stop at rest, and it rests against the WOT stop when the pedal touches, but doesn't activate, the kickdown switch.

I guess it's also possible that you got another bad MAF sensor.

I measured pins 2-3 and they show 12.0V, also all of the fuses look okay. The throttle rests against the idle stop at idle, and there is slight slack in the cable, also it rests against the stop at WOT just fine and moves smoothly. If it was a TPS problem, wouldn't that set a separate code than P0100? I also took apart the intake tract and made sure it was clean and seated correctly, then reassembled it and sprayed WD-40 on the intake system and other places where a vacuum leak might occur and it didn't change the idle or the way it runs. Is it possible that a faulty CPS could cause this?

Thanks,
Cameron
San Diego

>>I measured pins 2-3 and they show 12.0V, <<

How did you measure this while it was connected and running? Pierce the wires?

Thanks

it sounds like you've eliminated all culprits besides the MAF, which would point to the replacement being faulty as well. I agree that a faulty TPS should throw off another code.

_

Also check for 5 volt supply between pins 3 and 4. Output is not easy to check without adapter. If you can get to the wires with plug connected check for the output between pins 3 and 5. With ignition on should be 0.9 - 1.1V, engine idling about 1.3 - 1.7V and increasing with RPM increase.

I measured voltage by removing the connector and measuring pins 2-3 on the connector side with ignition on, but engine not running, is this the wrong way to do it? I'll try to use the tip of an X-Acto to pierce the insulation and put the leads on that today.

Thanks,
Cameron

you measure them at the pins like you already did.

Well, after much fiddling around, I just replaced the MAF and it fixed it Thanks for all the help, BTW I just replaced the insert, not the whole tube assembly, got the insert (Bosch new unit) for about $100, works fine, passes smog now, thanks!

Cameron
San Diego