EGR Solenoid Check
The EGR solenoid controls vacuum to EGR valve. The signal from ECM is Pulse Width Modulated (PWM), which changes cycle ("ON" time) from 0% to 100%. The solenoid operates on 12 volts supplied by ignition to solenoid. The ground circuit is completed through ECM. A vacuum fault will set a CEL and could result from a faulty EGR solenoid.
- This step checks for ignition voltage to terminal "G" of ECM. Normal reading is battery voltage.
- This step checks for EGR control by ECM. With engine at idle, voltage will drop below battery voltage as the PWM solenoid cycles. If voltage falls for 10 seconds, then goes back to battery voltage, the ECM has recognized a vacuum fault and has shut the EGR "OFF." Constant battery voltage indicates no ECM control. Normal reading is battery voltage with key "ON," and less than battery voltage and varying, with the engine at idle.
- This step checks for ignition voltage to EGR solenoid. Normal reading is battery voltage.
- This step checks for a grounded wire between ECM and EGR solenoid. Test light should normally be "OFF." 5 & 6) These steps check for proper resistance of EGR and EPR solenoids. Normal reading for a good solenoid is 20-40 ohms. If less than 20 ohms, ECM damage could result, and ECM must be replaced along with the solenoid. If resistance is 20 ohms or more, no ECM damage will occur.