Code 73 - EVO Actuator Circuit Open Or Shorted To Ground: Notes

When EBCM commands enable relay on, battery voltage is supplied to Electronic Variable Orifice (EVO) actuator. EVO actuator ground is provided by EBCM. EBCM controls amount of current supplied to EVO actuator based on input from wheel speed sensors and steering wheel speed sensor.

Code 73 can set before ABS initialization or when vehicle speed is greater than 10 MPH. Code will be stored, ABS/VES will be disabled, ABS warning light will illuminate and power steering returns to full assist. Code 73 will clear when setting conditions no longer exist and ignition key is turned off.

NOTE: Test numbers refer to numbers on diagnostic chart. Use only 10-megohm (minimum) DVOM for all voltage and resistance tests. For identification of circuits and terminals referenced in charts and text, see WIRING DIAGRAM .

Fig 1: Code 73 Diagnostic Flow Chart

Courtesy of GENERAL MOTORS CORP.

Checks for proper EVO actuator operation.
Checks for high resistance in EVO actuator control circuit.
Checks for short to ground in EVO actuator control circuit.
Checks for short to ground or high resistance in EVO actuator power feed circuit.
Checks for open in EVO actuator.
Ensures open or short to ground is not due to physical damage to circuitry.