GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 Epica 🢒 Engine 🢒 Engine Controls - 2.0L (L34 GMDAT) 🢒 DTC 045

Circuit Description

The electronic control module (ECM) supplies a voltage of about 450 millivolts between the ECM terminals D9 and C9. The oxygen sensor (O2S) varies the voltage within a range of about 1 volt if the exhaust is rich, down to about 100 millivolts if the exhaust is lean. The oxygen sensor is like an open circuit and produces no voltage when it is below 360°C (600°F). An open oxygen sensor circuit or a cold oxygen sensor causes Open Loop operation.

Conditions for Setting the DTC
    • The engine has been running for at least 60 seconds.
    • DTC 021, 022, 033, and 034 has not set.
    • The throttle angle is above 5 percent.
    • The engine coolant temperature (ECT) is above 70°C (158°F).
    • The engine controls system is in Closed Loop.
    • The oxygen sensor voltage is above 865 millivolts.
    • These conditions are present for at least 10 seconds.

Diagnostic Aids
    • Normal scan tool voltage varies between 100-999 millivolts while in Closed Loop.
    • Fuel pressure that is too high may cause a rich running condition.
    • A leaking fuel pressure regulator diaphragm will cause a rich running condition.
    • Inspect for leaking fuel injectors by performing a fuel injector balance test.
    • An intermittent throttle position sensor output will cause a rich running condition due to a false indication of the engine accelerating.
    • A false rich indication due to silicone contamination of the oxygen sensor. This will be indicated by the presence of the DTC 045 accompanied by lean driveability conditions and a powdery white deposit on the oxygen sensor.

Step

Action

Values

Yes

No

1

Was the Diagnostic System Check performed?

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Go to Step 2

Go to Diagnostic System Check - Engine Controls

2
  1. Connect the scan tool to the data link connector (DLC).
  2. Run the engine until it reaches operating temperature.
  3. Run the engine at 1,200 RPM.

Does the scan tool read the oxygen sensor (O2S) voltage fixed above the value specified?

865 mV

Go to Step 3

Go to Diagnostic Aids

3
  1. Disconnect the O2S connector and jumper the connector terminal to ground on the engine control module (ECM) side.
  2. Run the warm engine at idle.

Does the scan tool read O2S voltage below the value specified?

350 mV

Go to Diagnostic Aids

Go to Step 4

4
  1. Turn the ignition to LOCK.
  2. Replace the ECM. Refer to Engine Control Module Replacement .
  3. Road test the vehicle.
  4. Perform the Diagnostic System Check.

Is the repair complete?

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System OK

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