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.
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HOMESERVICE MANUALSMERCEDES BENZ1989420SELREPAIR AND DIAGNOSIS (SINGLE PAGE)BRAKESTRACTION CONTROLANTI-LOCK BRAKE SYSTEMTESTINGTEST 4TESTING DIODE IN HYDRAULIC UNIT
1989 Mercedes Benz 420SEL
Testing Diode In Hydraulic Unit
1989 Mercedes Benz 420SELSECTION Testing Diode In Hydraulic Unit
- Ignition on. Rotary switch to position 2. Multimeter set to DC volts position.
- Reading should be 0.4-1.5 volts. If less than 0.4 volts or greater than 1.5 volts, go to step 3).
- Check and replace valve relay or diode of hydraulic unit. Check connecting lines.
NOTE:
If ABS indicator light goes out upon replacement of
hydraulic unit with the ignition on and engine not running,
replace Electronic Control Unit.
RENDER: 1.0x
NO RELATED
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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.