Powertrain Controls - ECM/PCM

Code Chart 32:

EGR Valve Circuit:

CIRCUIT DESCRIPTION:

EGR valve operation is ECM controlled. A driver inside the ECM provides a ground source to the EGR Vacuum Switching Valve (VSV). By turning the VSV "ON" and "OFF," the ECM controls the vacuum source to the EGR modulator. The EGR modulator then regulates vacuum to the EGR valve using back pressure provided by the exhaust system. The ECM uses an EGR gas temperature sensor, mounted in the base of the EGR valve, for diagnosing if the EGR system is functioning properly. This temperature sensor contains a thermistor. The ECM provides a 5.0 volt reference and a ground for the sensor. The ECM monitors a change in the exhaust gas temperature to determine if the EGR valve is working when the EGR is commanded "ON." If the EGR valve fails to open, the gas temperature sensor signal will indicate "LOW" temperatures to the ECM. If the EGR valve is stuck open, the gas temperature sensor signal will indicate "HIGH" temperature to the ECM. AS a result, Code 32 will be logged in the ECM's memory, and the "CHECK ENGINE" light will come "ON." A failure in the EGR gas temperature circuit will also set a Code 32. Code 32 will set if the following conditions exist:

^ High temperature indicated at idle.
^ Low temperature indicated when EGR is commanded "ON."
^ Open or short in the EGR gas temperature sensor circuit.
^ One of the above conditions exist for 120 seconds.
EGR is not enabled if coolant temperature is below 69°C.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. Checks for the gas temperature sensors 5.0 volt reference.

2. Looking for a poor or open ground wire.

3. Checks for short to voltage or ground in sensor 5.0 volts reference circuit.

4. Checking the EGR gas temperature sensor's resistance.

5. A non-functioning EGR valve can cause Code 32 to set.

DIAGNOSTIC AIDS:

A poor connection or shifted EGR gas temperature sensor could cause a Code 32 to set. To check for a shifted sensor, monitor the sensor resistance at ambient temperature with a DVM connected to GRY/BLU wire and BLK wire. Start and run the engine noting the resistance change in the sensor as engine temperature increases. Refer to the Temperature to Resistance chart on the diagnosis chart. If the sensor fails the check, replace the sensor.