Test Step #3 - Diode (Hydraulic Unit/Solenoid Valve Relay)

Testing diode in hydraulic unit or in solenoid valve relay
NOTE: Modified hydraulic unit without diode in plug socket since 1986


TEST PROCEDURE:
With ignition on rotate tester switch to the #3 position


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RESULTS POSSIBLE CAUSES REMEDY

No Fault Found:
- ABS indicator lamp on
- Voltmeter reading 0.4V - 1.5V
- Battery LED on
- Alternator LED on
Go to TEST STEP #4, #5 and #6


Fault Found:
- ABS indicator lamp on Solenoid valve relay defective, Replace defective solenoid valve
- Voltmeter reading lower Diode of hydraulic unit or in relay,
than 0.4V or over 1.5V solenoid valve relay defective, Replace defective hydraulic unit
- Battery LED off Check for shorts and opens or in solenoid valve relay,
- Alternator LED off circuit wiring Check circuit wiring


NOTE: If ABS indicator lamp goes out upon replacement of hydraulic unit with ignition switched on and the engine not running, also replace electronic control unit as a consecutive damage of the defective diode.

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