Chart C3, EGR Solenoid Check
The EGR solenoid controls vacuum to the EGR valve. The signal from the ECM is Pulse Width Modulated (PWM), which changes the cycle (on time) from 0% to 100%. As the EGR solenoid cycles, control vacuum to the EGR valve is metered. The solenoid operates on 12 volts, supplied by the ignition. The ground is completed by the ECM to turn the solenoid on, allowing vacuum to the EGR valve. A vacuum error will set Code 53 and could be the result of a faulty EGR solenoid. When a vacuum error is sensed by the ECM, EGR is turned off. It takes approximately 10 seconds for the ECM to sense a vacuum error, and the CEL will not go off until the key is turned off.
NOTE:
The following step numbers refer to the numbers in the accompanying flow chart(s).
- 1) Checks for ignition voltage to terminal "G" of ECM. Normal reading will be 10 volts or more.
- 2) Checks for ignition voltage to EGR solenoid. Should normally be battery voltage.
- 3) This checks for EGR control by the ECM. With the engine at idle, voltage will drop below battery voltage as PWM solenoid cycles. If voltage falls for 10 seconds, then goes back to battery voltage, ECM has recognized a vacuum error and has shut the EGR off. Constant battery voltage indicates no ECM control. Normal voltage is battery voltage with key "ON", and below battery voltage and varying, with engine at idle.
- 4) Checks for a grounded wire between ECM and EGR solenoid. Test light should normally be off.
- 5 & 5A) Checks for proper resistance of EGR and EPR solenoids. Normal for a good solenoid is 20-40 ohms. If less than 20 ohms, ECM damage will result, and ECM must be replaced with the solenoid. If resistance is 20 ohms or above, no ECM damage will occur.