Bosch LH-Jetronic air mass sensor (Saab 9000)

V

Vesku

Guest
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
 
Are there any active components in there? I've got a few AMM's from Volvos
that have intact sensor wires but don't work, I haven't had time to open one
up and see what's in it though, pricey little things new though.

"Vesku" <vtmNOSPAM@sunpoint.net.invalid> wrote in message
news:bjajil$310$1@phys-news1.kolumbus.fi...
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
Click to expand...
 
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
Click to expand...
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
 
Lance Morgan wrote:
Vesku wrote:

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
Click to expand...
You're right they are not in Section 2.3 ;)

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
Click to expand...
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take off "ospam" to mail me
 
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