1. Home
  2. SAAB Cars Forum
  3. Bosch LH-Jetronic air mass sensor (Saab 9000)

Bosch LH-Jetronic air mass sensor (Saab 9000)

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

formatting link
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

Reply to
Vesku
Loading thread data ...

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

formatting link
[AMM input to ECU: 2.0V -Idling, 5.0V - Full Load] & Bentley wiring diagrams, for LH 2.2, AMM Voutput (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

Reply to
Lance Morgan

You're right they are not in Section 2.3 ;)

Reply to
Adrian England

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.