P0151

P0151-O2 SENSOR 2/1 CIRCUIT LOW







- When Monitored:
The downstream oxygen sensors are monitored for faults during the one-shot test and the catalyst monitor test. The one-shot test is activated after the upstream sensor has been used for closed-loop control for 98 seconds, with battery voltage between 11.0 and 16.0 volts. If the downstream sensor switches once whilst the test is active the test will be terminated. If it does not switch, the one-shot test will be continued to allow the diagnostic tests on the downstream sensor to execute until either a DTC is reported or the one-shot test times out after 160 seconds. The catalyst monitor test is activated after engine run time of 462.5 seconds, with battery voltage between 11.0 and 16.0 volts, vehicle speed between 55 and 150 km/h (34 and 93 mph) with variation of less than 8 km/h (5 mph), engine temperature above 70° C (158° F) and evap purge active. The test runs for a maximum of 60 seconds.

- Set Condition:
The oxygen sensor signal voltage is greater than 2.20 volts for a calibrated period of time. Two Trip Fault. Three good trips to turn off the MIL.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. O2 SENSOR BELOW 2.52 VOLTS
1. Start the engine.
2. Allow the engine to reach normal operating temperature.
3. With a scan tool, read the 2/1 O2 Sensor voltage.

Is the voltage below 2.52 volts?

Yes

- Go To 2

No

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Checking for an Intermittent DTC.

2. (K43) O2 2/1 SIGNAL CIRCUIT




1. Turn the ignition off.
2. Disconnect the 2/1 O2 Sensor harness connector.
3. Ignition on, engine not running.
4. With a scan tool, monitor the 2/1 O2 Sensor voltage.

Is the O2 Sensor voltage above 4.8 volts?

Yes

- Go To 3

No

- Go To 5

3. O2 SENSOR




1. Measure the voltage on the (K906) O2 Return Upstream circuit in the O2 Sensor harness connector.

Is the voltage at 2.5 volts?

Yes

- Replace the 2/1 O2 Sensor.
- Perform the PCM Verification Test.PCM Verification Test

No

- Go To 4

4. (K906) O2 RETURN UPSTREAM CIRCUIT SHORTED TO GROUND




1. Turn the ignition off.
2. Disconnect the C1 PCM harness connector.
3. Measure the resistance between ground and the (K906) O2 Return Upstream circuit in the O2 Sensor harness connector.

Is the resistance below 100 ohms?

Yes

- Repair the short to ground in the (K906) O2 Return Upstream circuit.
- Perform the PCM Verification Test.PCM Verification Test

No

- Go To 7

5. (K43) O2 2/1 SIGNAL CIRCUIT SHORTED TO GROUND




1. Turn the ignition off.
2. Disconnect the C1 PCM harness connector.
3. Measure the resistance between ground and the (K43) O2 2/1 Signal circuit in the O2 Sensor harness connector.

Is the resistance below 100 ohms?

Yes

- Repair the short to ground in the (K43) O2 2/1 Signal circuit.
- Perform the PCM Verification Test.PCM Verification Test

No

- Go To 6

6. (K43) O2 2/1 SIGNAL CIRCUIT SHORTED TO THE (K906) O2 RETURN UPSTREAM CIRCUIT




1. Measure the resistance between the (K43) O2 2/1 Signal circuit and the (K906) O2 Return Upstream circuit in the O2 Sensor harness connector.

Is the resistance below 100 ohms?

Yes

- Repair the short between the (K906) O2 Return Upstream circuit and the (K43) O2 2/1 Signal circuit.
- Perform the PCM Verification Test.PCM Verification Test

No

- Go To 7

7. PCM

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

1. Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test.PCM Verification Test

No

- Replace and program the Powertrain Control Module.
- Perform the PCM Verification Test.PCM Verification Test