Testing procedures sensors, TPS, intake air temp sensor and more

[shogun]

BMW 318/325/M3/525/535/M5 1989-1993 Repair Information
FUEL PUMP RELAY
OXYGEN SENSOR
DIAGNOSTIC CONNECTOR
FUEL INJECTOR
AIR FLOW METER
INTAKE AIR TEMPERATURE SENSOR
COOLANT TEMPERATURE SENSOR
THROTTLE POSITION SWITCH
IDLE SPEED ACTUATOR
CYLINDER IDENTIFYING SENDER
ENGINE SPEED SENSOR

Courtesy of: http://www.autozone.com/repairguides...00c1528004a161

[shogun]

This may help especially those of us like me, which are not that good in electrics/electronics as a DIYer and need some guidance how to do a simple DIY test of electric/electronic components in our car.
Simple instructions how to test relays http://www.wikihow.com/Test-a-Relay
All you really need to do this is a multimeter set on resistance, however, a 12 volt car battery could be useful. If a car battery isn't available, you can manually close the coil in the relay.
https://www.youtube.com/watch?v=_gIZ0weS7iU
How to Test a 3, 4 or 5 Pin Relay - With or Without a Diagram https://www.youtube.com/watch?v=IpRW...cztkEWiVy-XMaQ

What you need is a electronic contact cleaner and contact enhancer like DeoxIT or Stabilant 22A which BMW is using. Not similar to flushing type contact cleaners, DeoxIT or Stabilant, Wurth and some others dissolve oxidation on metal surfaces. This is especially important on older equipment and equipment exposed to severe environments (humidity, salt, and other contaminants). Dissolving oxidation lowers contact resistance, thereby increasing conductivity even more.
Stabilat 22A is even recommended in the BMW TIS.
Stabilant 22A Electrical Contact Enhancer Model: All BMW
Complaint:
Connectors which carry low current are more likely to form deposits which affect the resistance of the circuit through the plug connector. Depending upon the particular circuit these deposits can cause malfunctions and consequently activate warning lamps and check control indicators.
Remedy:
Part replacement can temporarily stop the problem.
If the connector is the problem then without disconnecting the connector measure the resistance of the circuit running through the connector to make sure the connector has a high resistance. A good resistor will have close to 0 ohms resistance.
Visually examine the male and female terminals in the connector housing by removing them. Look at the integrity of the wire crimps, and in some male terminals the integrity of the weld of the male pin to the terminal. Then reinstall.
With a zero residue electrical contact cleaner liberally spray the male and female connectors, and allow the air to dry.
Apply Stabilant 22A to both male and female terminals so they are saturated, and reconnect the connectors while they are still wet. When the Stabilant 22A dries it will leave a thin coating of polymer film which is conductive between mating surfaces, and is non-conductive between adjacent pins. It can also prevent the formation of more harmful deposits.

[PDF] Understanding European DIN Wiring Diagrams http://www.thesamba.com/vw/archives/...April_2003.pdf download it

[Jazz_89]

Nice links, thanks.

I measured 5000 Ω resistance from my coolant temp. sensor (cold engine) while the Hayes Manual says 2100-2900 Ω ...
On the first link with the testing procedures, the author often refers to a chart for looking up values. Do you have this as well? I was wondering if it contains different values than the manal

[shogun]

What means cold engine where you live? Minus 10 degree Celsius or + 10,20,30 ?

Check also here in the workshop manual under nominal values https://www.bmwtechinfo.com/repair/main/
As the E34 535 has the same engine as the E32 735 I just checked in my Bentley Repair manual for the E32:
M30 has 3 temp sensors in case engine is with EML, otherwise 2:
left to right, in thermostat housing
1. temperature gauge sender
2. engine coolant temperature (ECT) sensor (DME)
3. EML coolant temperature sensor (in case the engine has EML)

wire colors DME 1.3 Motronic M30
gauge sender: brown/violet-brown/yellow
ECT sensor: brown/red-brown/orange
EML temp sensor: brown/red-blue violet

resistance values NTC blue for temperature indicator, temperature sensor, also valid for all other 2,5 kOhm-Sensors http://www.e32-schrauber.de/bmw/date...u-2_5-kohm.png
you can see even 10 degree C makes a big difference
0 DC 5896
10 DC 3792
20 DC 2500

http://www.e32-schrauber.de/bmw/

CTS
The CTS is immersed in the coolant system and contains a variable resistance that operates on the NTC principle. When the engine is cold, the resistance is quite high. Once the engine is started and begins to warm-up, the coolant becomes hotter and this causes a change in the CTS resistance. As the CTS becomes hotter, the resistance of the CTS reduces (NTC principle) and this returns a variable voltage signal to the ECU based upon the coolant temperature. The open circuit supply to the sensor is at a 5.0 volt reference level and this voltage reduces to a value that depends upon the resistance of the CTS resistance. Normal operating temperature is usually from 80° to 100° C. The ECU uses the CTS signal as a main correction factor when calculating ignition timing and injection duration.

[Jazz_89]

Edited

Thanks for the info. It was about 5° C here, so I guess the reading is OK according to this table. I will also test it at operating temperature.
I also checked the throttle position sensor and noticed that the WideOpen-Switch closes a little earlier before the throttle shaft reaches its maximum position. This probably means that the air-fuel mixture gets richer much sooner^^ They probably designed it this way, because the air flow does not increase a lot with throttle angle near the max. range. Anyway, I think that adjusting the TPS to activate later the WideOpen-Circuit could reduce max power, but also fuel consumption and probably emissions.
Greets

[shogun]

For the M1.3 for the M30: if you go to the ETM version 02/1989 you see on page 1210.2-01 the diagram for injection electronics.
There it is very simple for the throttle valve, it only detects via the throttle switch
1. idle speed
2. full speed

and there is 3. to mechanical linkage (with AEGS) = cars with automatic trans, so only in case of cars with automatic transmission with AEGS the AEGS control module gets the info about the opening angle.

https://www.bmwtechinfo.com/repair/m...es/7410275.jpg
dynamic check of idle speed control valve https://www.bmwtechinfo.com/repair/m...es/7410281.jpg

You either have continuity at WOT or you do not.

On M20 and M30 engines, a throttle position switch provides an idle and full throttle position signal to the ECM. If you are reading (measuring) this with a multimeter and using the signal setting (beep) on the Ohm scale you will get a beep at closed throttle and a beep and WOT. Not much more simple than that. The entire procedure on testing this is in the Bentley page 130-8 in the Fuel Injection DME section.

[Jazz_89]

Cool, I found the corresponding circuit diagram and the testing procedure. I was just wondering that the WOT beep begins to sound already like 10° before it reaches wide open throttle.

[Jazz_89]

Alright so I am about to test the oxygen sensor voltage during idle and during middle RPM and therefore I want to identify these cables coming out of the sensor. There are four cables on the sensor side. two white, one grey and one black. I guess the two whites are for the heating, the grey is a ground and the black is the signal to the DME?




But here in the electric diagram manual, there are different colors for the connector? Is this because they are showing the other side of the connector (the one to the DME)? Plus, what are these curly brackets?


Thanks!

[Jehu]

Can we use a MAF Sensor replacement like these?

The fit into the stock housing but are a different type of sensor.. will their output work with the BMW ECU?

http://www.ebay.com/itm/141296721307...S:1123&vxp=mtr

The unit pictured it the type shipped.