Open loop, close loop
#1
Open loop, close loop
I wanted to align the idle RPM in open loop and close loop mode. So I started to measure and the result (although not related to the original intent) is as follows, all measurements with an oscilloscope, engine warmed, running, LUCAS P, 16ECU, USA model, V12, 1988, two connectors, 4 pin (test) and 2 pin (switch) in boot:
O2 sensors disconected from wire to ECU:
A bank - 0.6V
B bank - 0.5V
Reading disconnected wire to ECU:
A bank - 4.8V
B bank - 4.9V
O2 sensors conected to ECU, reading from connectors in engine bay:
A bank - 3.3V
B bank - 1.5V
OPEN LOOP, 780 RPM
Output on the 4-pin connector, square waves, A + B bank 1.9 V (it is all right, as described in Book)
CLOSE LOOP, 880 RPM
Reading from 4-pin connector, GW (A bank) and GK (B bank) in boot
A bank - square waves, 1.9V, something is bad
B bank - 3,7V
Result :
A bank is running in close loop mode in "map" mode
B bank is running (perhaps) in close loop mode in "O2 sensor mode"
O2 sensors are new (2 month old), ECU is refubrished.
Where to start to find solution ? Thanks
O2 sensors disconected from wire to ECU:
A bank - 0.6V
B bank - 0.5V
Reading disconnected wire to ECU:
A bank - 4.8V
B bank - 4.9V
O2 sensors conected to ECU, reading from connectors in engine bay:
A bank - 3.3V
B bank - 1.5V
OPEN LOOP, 780 RPM
Output on the 4-pin connector, square waves, A + B bank 1.9 V (it is all right, as described in Book)
CLOSE LOOP, 880 RPM
Reading from 4-pin connector, GW (A bank) and GK (B bank) in boot
A bank - square waves, 1.9V, something is bad
B bank - 3,7V
Result :
A bank is running in close loop mode in "map" mode
B bank is running (perhaps) in close loop mode in "O2 sensor mode"
O2 sensors are new (2 month old), ECU is refubrished.
Where to start to find solution ? Thanks
Last edited by roman_mg; 05-11-2018 at 04:30 AM.
#2
#4
I made yesterday experience. I link A-bank lambda to B-bank wire to ECU and B-bank lambda to A-bank. Result :
Reading from 4-pin connector, GW (A bank) and GK (B bank) in boot
A bank lambda - 3,7V
B bank lambda - square waves, 1.9V
It seems, that wires for A-bank are all right and ECU too, and bad is lambda in A-bank. I will try change A-bank lambda and we will see
Reading from 4-pin connector, GW (A bank) and GK (B bank) in boot
A bank lambda - 3,7V
B bank lambda - square waves, 1.9V
It seems, that wires for A-bank are all right and ECU too, and bad is lambda in A-bank. I will try change A-bank lambda and we will see
#5
You can not read O2 sensors reliably with a DVM unless the DVM has peak hold function, you really need to look at the waveform on a scope. This is essentially an AC voltage and measuring with a DVM on DC will give not work as the O2 sensor pulses too quickly, and measuring on AC you will read the RMS value of the average of what the O2 sensor is reading.
Rich will be 0.9v and lean will be 0.1v
If your DVM has peak/min hold use these functions with DVM set to DC to measure max and min voltage
Rich will be 0.9v and lean will be 0.1v
If your DVM has peak/min hold use these functions with DVM set to DC to measure max and min voltage
Last edited by warrjon; 05-12-2018 at 05:46 PM.
#7
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#12
I have a vague recollection that on some old ECUs a DC offset is added. That would be more obvious if a reading was taken with the sensor disconnected.
#13
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