oxy sensor testing at the DME/MOTRONIC in E-box

[shogun]

750 with DME -352
Lambda/oxy sensor on pin 70, and Lambda/oxy sensor ground on pin 71


750 M70 engine -156 (pre-facelift)
Pin 28 (+) and Pin 10 (-)
cable colour according to Bentley Repair Manual E32 page ELE-72 Pin 28: Schwarz/black, Pin 10: Gelb/yellow

750 has 4 modules in the E-box. From left (window) to right (front of car): DME I for cylinder bank 1-6, then EML, then DME II for cylinder bank 7-12, the one next to the shock mount is the ABS/ASC Module!
Zylinder row 1-6 is passenger side (LHD), 7-12 is driver side (LHD= left hand drive), always counted from front of engine = 1 and 12 are closest to the window/firewall

730 R6/straight 6 production 05/ 90 (as example) M30B30 or M30B35 engine, MOTRONIK with Bosch Nr. -150 or -179, Pin 28 Lambda/oxy sensor, Pin 10 is ground

M60B30 V8 and M60B40 V8 engine,730 and 740 E32 : cylinder row 1-4 are pins 13(SW/black-white) and 40(GE/yellow), for cylinder row 5-8 12(SW/black-white) and 39(GE/yellow)

Remove the cover from the MOTRONIC plug, insert the plug again into the DME, the pin numbers you can read then or count them. Please check again in the Bentley Manual or in the wiring diagrams the correct pins.

Let car idle till the cats are at operating temperature.. Check with a voltmeter. The voltage should fluctuate between 0.2-0.8 V. within 1 second at least 1 time. The faster the better the oxy sensor is responding. Older ones get 'lazy'. In case the voltage is constant, the corresponding oxygen sensor is defective. In case the voltmeter is at 0.45V, then wait till engine gets warm and the voltmeter starts to fluctuate. Then it should start regulating/fluctuating.

Checking at the MOTRONIK is easier, no need to crawl under the car. But when removing the screws from the MOTRONIC plug cover, pay attention not to drop one into the E-box. To get the screw out again, you might have to remove all modules ;-)

cables on our oxy sensors: heated oxy sensor: schwarz/black - Signal, grau/grey - Masse/ground*, 2x weiß/white for heating of the oxy sensor.

Unbeheizte Sonde/unheated oxy sensor: 2x schwarz/black - Signal und /and Signalmasse/signal ground* . Bei einigen Sonden Masse über das Gehäuse/in case of some oxy sensors the ground is via the housing.

Motronic !.3 pinout http://www.e38.org/e32/m1_3.pdf

ECU/MOTRONIK 750 1988-1990 pin details http://www.e38.org/e32/750ilpinout1988_90.pdf

Pic from M70 M1.7 Bosch end # 352


Download the pic to your PC!. That free upload server kicks the pic out and deletes it after 200 days.

from oxygensensors dot com

What is an oxygen sensor?
An oxygen sensor is a measuring probe for determining the oxygen content of the exhaust gas. Since the amount of oxygen in the exhaust gas indicates precisely how complete the combustion of the air-fuel mixture in the cylinders is, it is also the best starting point for controlling the air-fuel ratio.

How do they work?
The oxygen sensor is strategically located in the exhaust system. The outside surface of the ceramic measuring tube protrudes into the exhaust gas flow, and the inner surface is in contact with the outside air. A voltage is generated at the interface which is proportional to the relationship between residual oxygen in the exhaust gas and that of the surrounding air. When this relationship changes, so does the voltage. This voltage is processed by an electronic control unit (ECU) into a control signal for influencing the air-fuel mixture through controllable fuel injection or carburetor systems. The exhaust gas composition is thus always maintained at that level which permits effective after-treatment by the vehicle's catalytic converter.

Why should I change my oxygen sensors?
A new oxygen sensor can improve driveability and lengthen engine life. Ultimately, you achieve a smoother running engine that is more fuel efficient. Feedback from the oxygen sensor provides closed-loop control of the injected quantity of fuel for optimum air-fuel mixture...enabling virtually complete combustion to take place. By providing closed-loop control of the mixture, it becomes possible to use three-way catalytic converters to achieve the maximum reduction in exhaust gas emissions.

How often should I change them?
Your vehicle manufacturer recommends a specific mileage at which your oxygen sensor(s) should be changed. However, contaminants in gas and certain atmospheric conditions can drastically shorten the life of any oxygen sensor, therefore they should be checked with every periodic maintenance and changed if necessary. Below you can find a visual reference of oxygen sensor problems as well as diagnostic procedures.

All About Lambda Sensors
The exhaust gas oxygen sensor (EGO or O2), or lambda sensor, is the key sensor in the engine fuel control feedback loop. The computer uses the O2 sensor’s input to balance the fuel mixture, leaning the mixture when the sensor reads rich and enriching the mixture when the sensor reads lean.
Lambda sensors produce a voltage signal that recognises the amount of unburnt oxygen in the exhaust. An oxygen sensor is essentially a battery that generates its own voltage. When hot (at least 250 °C), the zirconium dioxide element in the sensor’s tip produces a voltage that varies according to the amount of oxygen in the exhaust compared to the ambient oxygen level in the outside air. The greater the difference, the higher the sensor’s output voltage.
Sensor output ranges from 0.2 volts (lean) to 0.8 volts (rich). A perfectly balanced or "stoichiometric" fuel mixture of 14.7 parts of air to 1 part of fuel gives an average reading of around 0.45 volts.
The lambda sensor’s output voltage doesn't remain constant, however. It flip-flops back and forth from rich to lean. Every time the voltage reverses itself and goes from high to low or vice versa, it’s called a “cross count”. A good O2 sensor on a injection system should fluctuate from rich to lean about 1 per second. If the number of cross counts is lower than this, it tells you the O2 sensor is getting sluggish and needs to be replaced.
Most lambda sensors will cycle from rich to lean in about 50 to 100 milliseconds, and from lean to rich in 75 to 150 milliseconds. This is referred to as the “transition time”. If the O2 sensor is taking significantly longer to reverse readings, this too is an indication that it is getting sluggish and may need to be replaced.
Observing the sensor’s waveform on a scope is a good way to see whether or not it is slowing down with age. If the sensor becomes sluggish, it can create hesitation problems during sudden acceleration.

Heated Oxygen Sensors
To reduce the warm-up time of the lambda sensor, an internal heating element may be used. Heated O2 sensors can reach an operating temperature of as high as 500 degrees C in as little as eight seconds! Shorter warm-up time means the system can go into closed loop fuel control sooner, which reduces emissions and improves fuel economy. Heating the sensor also means it can be located further downstream from the exhaust manifold. from how stuff works


Our self made test unit on a B12 Alpina 5.0 750 https://www.youtube.com/watch?v=K8mi...e=channel_page

This is actually a Mixture Display Kit For Fuel Injected Cars , bought that more than 10 years ago from Jaycar online shop, CAT. NO. KC5195 , Mixture Display Kit For Fuel Injected Cars , Refer: Silicon Chip November 1995 This very simple kit will allow you to monitor the fuel mixtures being run by your car. This type of sensor is also known as an E.G.O. (exhaust, gas, oxygen) monitor. You can use it as a tuning tool, to help in vehicle modification or simply to see the behaviour of the engine control module. Indication is via 10 LEDs to show mixtures rich, lean and normal. The circuit connects to the EGO sensor mounted in the exhaust manifold and the cars battery. PCB, LEDs and components supplied.

The plugs you have to get from an old oxy sensor and the counter part from a wire loom from under the car. I am still checking if they are available as single item from BMW.

[shogun]

here a picture how to test the O2 sensor at the pins of the motronic, for the pin numbers see above post

[LysanderSpooner]

Looking for instructions for this for the M60 740i but coming up blank. Any ideas?

UPDATE: looks like I found it:

screen-grab- 2021-08-10 at 9.59.05 AM.png

Pins 13 & 40 for cylinders 1-4 and 12 & 39 for 5-8.

[shogun]

For M60B30 V8 + M60B40 V8 730 + 740 E32 : cylinder row 1-4 are pins 13 (SW/black-white) + 40 (GE/yellow), for cylinder row 5-8 12 (SW/black-white) + 39(GE/yellow)

[shogun]

here a tester we made ourselves almost 20 years ago, using old O2 sensor connectors to see the result with running engine https://www.youtube.com/watch?v=K8miz_1aHYw
test was done on an Alpina B12, it started slowly as the exhaust was still cold and the O2 sensor needs heat to start regulating.
the o2 tester is actually a exhaust, gas, oxygen monitor. I bought that kit from Jaycar Australia many years ago. Mixture Display Kit For Fuel Injected Cars CAT. NO. KC5195. Refer: Silicon Chip November 1995 This very simple kit will allow you to monitor the fuel mixtures being run by your car. This type of sensor is also known as an E.G.O. (exhaust, gas, oxygen) monitor. You can use it as a tuning tool, to help in vehicle modification or simply to see the behavior of the engine control module. Indication is via 10 LEDs to show mixtures rich, lean and normal. The circuit connects to the EGO sensor mounted in the exhaust manifold and the cars battery. PCB, LEDs and components supplied.

But we soldered it together and found it not 100% accurate when testing with a FLUKE, so my buddy soldered in a resistor. Then we just added the plugs (1 with short wires as it comes from MOTRONIC, and the other one as it comes from the oxy sensor. This we just connect under the car in between the original connection and let the engine run, so after some time of warm up of the cat the lights start to move. Very easy to see if the oxy sensor works or not. I had a bad sensor, easy to see, no movement of the lights at all. Of course you can also test it on the cables of the MOTRONIC in the e-box. On my -156 MOTRONIC pin 10 and 28 if I remember correct (check the Bentley, easy to find). Then open the e-box, remove the connector from the MOTRONIC, then remove the 2 screws outside from the connector which holds the cover of the connector. Then pull the inside out where all the wires with the pins are actually connected. Then plug that stuff onto the MOTRONIC again. Then you have from the top of the connector access to the pins in the plug. Connect that unit or a voltmeter. If you have long wires for the DMM, put the DMM in the car on the center console and the wires thru the open window, close the hood and you can even drive the car while monitoring the oxy sensor.
On a -352 MOTRONIC the pins are different numbers. See ETM.

[shogun]

Bentley repair manual page 130-9 oxygen sensor testing, excerpt
O2 sensor provides an input voltage signal 0-1VDC to the ECM. To generate voltage, the sensor temperature must exceed 600 degree F. Therefore the sensor is heated. M30 1 sensor, M60 and M60 2 sensors. One for each cat.
The test given below is not a conclusive test of O2 sensor efficiency and does not test how quickly the O2 sensor reacts to changing conditions. For most exact/accurate test an exhaust gas analyzer should be used.
Connect a digital voltmeter to pins 1 and 2 (black wire, yellow wire) in O2 sensor connector. Leave connector attached. Note: O2 sensor terminal identification can vary. Consult ETM for details. O2 sensor connaction location , 4-pin, black
M30 rear of engine compartment, lower left hand side
M60 beneath car, under transmission, same for M70

Start the engine and let it idle. The O2 sensor should start to produce a fluctuating voltage within a short period. If the voltage is incorrect, turn the engine off and check the pre heater circuit

voltage at idle: 0.2 - 0.8 VDC, fluctuating
to check the sensor response to lean and rich mixtures, create an air leak, or pull vacuum hose off fuel pressure regulator to increase fuel pressure.

Separate sensor harness connector from the sensor. Check for battery voltage between terminals 3 and 4 in harness side of connector with engine running. If voltage is not present, check that O2 sensor heater relay is functioning correctly. See ETM.
The O2 sensor heater relay is energized with positive + battery voltage from the main DME relay and a switched ground from the ECM. On some DME systems the O2 sensor heater circuit is not controlled by a relay.
Check heater element resistance between terminals 3 and 4 in sensor side of connector. If element is electrically open (no continuity) , replace sensor.
If O2 sensor is not producing a fluctuating voltage and preheater circuit is ok, replace sensor.
Tightening torque of O2 sensor to exhaust: 55 Nm, 41 ft-lb

if not already applied, coat O2 sensor threads with seize compound before installation. Do not get compound on sensor tip.

[shogun]

SI Oxygen Sensor - Thermoshock E31 E32 M70
Rough or hunting idling and/or clutch judder when driving. "Check engine" lamp comes on in US vehicles.

An increasing amount of water collects in the exhaust system due to unfavourable driving conditions such as frequent stop-and-go driving, long periods of idling and a lot of short-distance driving. This water builds up through e.g.:-separation of the water content in the fuel during cold start-as a product of the combustion process-through condensing of the air moisture in the exhaust as the exhaust system cools down.The ceramic sensor body that is heated immediately after the engine is started and quickly
achieves a high temperature is damaged by this cold condensate (thermoshock).The following fault codes may be stored in the DME fault memory.
DME M1.2:
"10" - Oxygen-sensor control and/or
"28" - Oxygen sensor
DME M1.7:
"70" - Oxygen sensor and/or
"201" - Oxygen-sensor control
Affected vehicles:E31, E32 with M70, Manufacturing period: from start of series production up to October 1994.
Remedy
If the oxygen sensor malfunctions repeatedly, not only the oxygen sensors must be replaced, but a Service solution must be retrofitted that has the following effect: delay of
oxygen-sensor heating after the engine is started, depending on the engine temperature and the engine load.
1. Replace the oxygen sensors and clear the DME fault memory.
2. Retrofit the Service solution consisting of an "oxygen-sensor-heater relay" and Service wiring harness
.-Enclosure 1 contains a description of how to install the Service solution in E32 M70 vehicles with oxygen-sensor-heater relay (LSH) (manufacturing period:
11/86 up to 01/91 and 03/92 up to 03/94).
-Enclosure 2 contains a description of how to install the Service solution in E32 M70 vehicles without oxygen-sensor-heater relay (manufacturing period: 02/91 up to 02/92).-Enclosure 3 contains a description of how to install the Service solution in E31
M70 vehicles with oxygen-sensor-heater relay (manufacturing period: 07/89 up to 01/91 and 03/92 up to 10/94).
-Enclosure 4 contains a description of how to install the Service solution in E31 M70 vehicles without oxygen-sensor-heater relay (manufacturing period: 02/91 up to 02/92).
https://workshop-manuals.com/bmw/7_s...k_e31_e32_m70/

O2 sensor testing https://www.bimmerforums.com/forum/s...sensor-testing