April 2019

APRIL 2019 AFTERMARKET 55 www.aftermarketonline.net the wheel speed sensor circuit to erase any DTC related to open–short before testing the circuit, as the control unit will not turn the power supply back on until this is erased. Passive Inductive or passive sensors are different. These are not powered units but again, if the control unit detects an open short, then this time it may send a power supply to the sensor so the sensor will not operate in this situation. The sensor is easily checked with a scope; probe both wires with the sensor disconnected from the control unit and you should have a nice sign wave or analogue signal on both wires. If you do not have a scope then normally these will have a service standard for their resistance. The best way to check the resistance of the sensor is to disconnect the ABS unit and check the resistance across the two wires at the control unit connector. That way, you are also checking the circuit and the sensor in one test, if you do have an abnormality you can then check the sensor with it disconnected from the circuit. If this is OK, you know you have a circuit fault in-between the control unit and the sensor. Of course, these also use a tone wheel, so all checks relating to these and wheel bearings also apply. Remember again to clear any DTCs before testing speed sensor circuit. ANTI WERFUL PO CLEAN CTERIAL BA USEOY EAS SC LEMON T FRESH E . 0871 288 7125 CALL S ASTS LT ENT THA - WEEK W . COM . SALES@POWERMAXED MAIL COM . .POWERMAXED WWW EB Right: If you have a DTC indicating ‘range performance intermittent’ you may still have a power supply