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 O2S is like an open circuit and produces no voltage when it is below 360°C (600°F). An open O2S circuit or a cold O2S causes Open Loop operation.
• | The engine has been running for at least 60 seconds. |
• | DTCs 021,022, 033, 034 has not set. |
• | The throttle angle is above 5 percent. |
• | The coolant temperature is above 70°C (158°F). |
• | The O2S is steady between 340-550 millivolts. |
• | These conditions are present for 20 seconds. |
Normal scan tool voltage varies between 100-999 millivolts while in Closed Loop.
Step | Action | Values | Yes | No |
---|---|---|---|---|
1 | Was the Diagnostic System Check performed? | -- | Go to Step 2 | |
2 |
Does the engine control module (ECM) go into Closed Loop? | -- | Go to Step 3 | Go to Step 8 |
3 |
Does the scan tool read the oxygen sensor input toggling between the specified values? | 100-900 mv | Go to Step 7 | Go to Step 4 |
4 |
Is the lead properly attached to the sensor? | -- | Go to Step 5 | Go to Step 9 |
5 |
Does the oxygen sensor input stay fixed at or less than the specified value? | 300 mv | Go to Step 6 | Go to Step 8 |
6 |
Does the oxygen sensor input stay fixed at or greater than the specified value? | 600 mv | Go to Step 7 | Go to Step 8 |
7 |
Did DTC 013 reset in the ECM? | -- | Go to Step 2 | |
8 |
Is the voltage within the specified range? | 300-600 mv | Go to Step 9 | Go to Step 10 |
9 |
Did you complete the repair? | -- | System OK | -- |
10 | Inspect for an open or short to ground between the oxygen sensor connector and the ECM connector terminal D9. Is the problem found? | -- | Go to Step 11 | Go to Step 12 |
11 |
Did you complete the repair? | -- | System OK | -- |
12 |
Did you complete the repair? | -- | System OK | -- |