neilh

To our LH experts, on a S4 -

If pin 5 on the MAF is either
1) shorted to ground, or
2) shorted to +12,

what would be the expected result, problem, ?

A schematic of the LH would be nice if anyone cares to share


Asking because i just helped a friend diagnose a problem, and this was the likely cause.

John Speake

Pin 5 is the MAF output to the LH ECU.

What do you mean by shorted to ground ? If you measure pin 5 to the case of the disconnected MAF which is ground then you will measure a low resistance - about 4 ohms. (Pins 3 & 4 are also ground to case)

If pin 5 is 12v when plugged in with ignition on then there's probably a shorted wire in the 6 way plug. Don't leave it like that as the hot wire will probably fuse.

The rest iof the pins are

neilh

John,
With the MAF removed from the intake, but plugged in to the 6 way plug, moving the harness at the plug causes the car to stumble and die. Upon removing the cover at back of plug it was apparent that wire on pin 5 was shorting to either pin 3 or 4, or to pin 2, as all had exposed wiring.

Cheers,
Neil

John Speake

Ok, good ! You can buy new 6 way connectors with pins and boot from Roger.

firemn131

Hey Neil,

PM sent

PorKen

Don't look at me! Electronics have not been an easy subject for I and I. I am glad JS chimed in as he is the expert.

Here is the only schematic that I know of for LH 2.3 (by Chris) with correction and annotation balloons by me as much as I could determine/understand from reading the code and testing.
http://members.rennlist.org/porken/928_lh5_new.pdf

LH 2.4 for Volvo is similar and can be helpful sometimes.
http://ipdown.net/jetronic.info/tiki...s+and+Diagrams

neilh

LOL, thanks Ken, thats what i needed,.
From the volvo info, either a permanent ground or +12 would confuse the heck out of it, as the range is shown as 1.4 at ign on, 2.3 at idle, and increasing with load.

Cheers,

neil

scottpeterd

It's funny this should come up on this forum. I'm restoring an S600 Mercedes with a V12. Two LH systems. And I'm having problems with the MAF not being read by the LH computer on one bank. The diagram is just what I needed

Cheers

John Speake

The "problem" is that some of the ICs in the MAF signal path are custom devices with no data or spares.

Randy V

Yo, Neil - you want Alan, not Porken when it comes to understanding electrons.