Date: Sat, 6 Sep 2003 10:42:24 -0500 From: Lance Morgan <alancemorREMOVEnopsamoCAPS.com> Subject: Re: Bosch LH-Jetronic air mass sensor (Saab 9000)
Vesku wrote: > Hotwire broken from the sensor that was working (A). I had another > sensor > unit (B), wires seem ok but did not work, with B no check engine > light. > > Airmass sensor is Bosch type 0280212005, picture on > http://www.speedparts.se/prod/res_fuel_luft.shtml > > I changed the two circuit boards that are under the black plastic > cover, > from A to B, thinking that there was something wrong in the > electronics > part of B, not in wires/resistors. I cut the 6 connections from side > connector, 3 screws with screwdriver (and drill where needed), removed > 6 > solderings to the wires/resistors on the middle by suction. Thin wires > locate quite easily if holes are clean. Finally soldered the side > connector > clips. > > But after changing, function remained same. So there is probably > something > wrong in wires/resistors of B as well, electronics could be ok in > both. I > also tried the sensor to a "reference car", it seems quite sure the > fault > is in airmass sensor, not ECU or some other sensor. > > According to Bentley's "Bosch Fuel Injection and Engine Management" > book, > the 6 wires soldered to PCB, are connected to resistor in frame (2 > wires), > hotwire (2 wires), temperature compensation resistor (2 wires). But > there > is no information about values et.c. What could be measured from the > sensor > disconnected / with power switched on / engine running ? > > And is there information, links, et.c. about Saab or some other Bosch > LH > airmass sensor (Audi, BMW, Volvo et.c..) schematics, or other info on > the > web ? > > br Vesku afaik, the "real" AMM test is a bench environs w/critically controlled variable airflow, measuring V output (it doesn't appear to be linear). The output specs must be out there - either Bosch or commercial AMM remanufacturing companies - but likely impossible to obtain (even more so w/the inner working/micro component specs). I don't believe - but am not sure - that they are in the Saab Factory Manual Section 2:3; Fuel System - Fuel Injection 81-93; PN 03 48 425 From "Bosch Fuel Injection and Engine Management" by Charles O. Probst; ISBN: 0837603005 "With engine running at normal temperature, the voltage should typically read 2.12 V at 760 RPM, and increase to 2.83 V at 3520 RPM. Changes are more important than the actual numbers." From http://www.scotsglen.com/saab/ecu/ [AMM input to ECU: 2.0V - Idling, 5.0V - Full Load] & Bentley wiring diagrams, for LH 2.2, AMM V output (same as input to ECU) should be measured at AMM pin/harness #5 It sounds like you've already swapped in another AMM, from a good-running car, and it fixed the problem car (which is what most pro shops do to AMM, afaik) In some locales 005s are moderately easy to find & fairly inexpensive - but perhaps not where you are located - but getting yet a 3rd used whole AMM would probably be the best course out hth Lance
 |
 |
 |
 |
 |
