Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1990 BMW 535iFACTORY OEM SERVICE PROCEDURE
Sensor & Circuit Checking Procedure
- With ignition off, remove connector from the sensor, located on front of engine near crankshaft pulley.
- Turn ignition on and check voltage at Black wire of connector. Voltage should be approximately 5 volts. If voltage is not within specification, check wiring circuit between MCU pin No. 47 (Black wire) and sensor.
- Check voltage between both terminals of the sensor connector. Voltage should be approximately 5 volts. If voltage is not within specification, check wiring circuit between MCU pin No. 48 (Yellow wire) and sensor.
- If all voltages are correct, reinstall sensor connector. Sensor can be checked with ohmmeter or oscilloscope. Ensure ignition is off. Unplug sensor.
- Resistance across 2 connector terminals (sensor side) should be as specified. See ENGINE SPEED/REFERENCE POINT SENSOR table. Connect ohmmeter between each sensor terminal and engine block. Ohmmeter should not show continuity. Replace sensor if continuity exists.
- To check sensor with oscilloscope, unplug sensor. Connect oscilloscope leads across the 2 sensor terminals. Remove fuel pump relay to prevent engine from starting. Crank engine. Oscilloscope should show a sine wave as engine is cranked.
ENGINE SPEED/REFERENCE POINT SENSOR
| Application | Ohms |
|---|---|
| All Models | 490-550 |
Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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