P2A01

P2A01-O2 SENSOR 1/2 CIRCUIT PERFORMANCE









For complete wiring diagrams refer to Diagrams/Electrical.


Theory of Operation

The engine aftertreatment system monitors the O2 content in the diesel engine exhaust. The ECM monitors the exhaust gases for oxygen content and varies the rich/lean fuel mixture of the intake air fuel mixture to adjust the system. This diagnostic checks to make sure that the O2 content matches the expected O2 content for the engine operating conditions. The ECM will set the fault if it detects that the actual O2 measurement does not match the expected value. The ECM will illuminate the MIL lamp immediately when the diagnostic runs and fails. The ECM will turn off the MIL lamp diagnostic runs and passes in four consecutive drive cycles.

- When Monitored:

This diagnostic runs when the engine is running.

- Set Condition:

The ECM will set the fault if it detects that the actual O2 measurement does not match the expected value.







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.


1. OXYGEN SENSOR 1/2





Disconnect the Oxygen Sensor1/2 harness connector.


NOTE: Check connectors - Clean/repair as necessary.

Measure resistance of the 02 sensor heater between the (K299) 02 heater supply and (K80) 02 heater return circuits.

Is the resistance 3.2 ± 0.8 ohms at ambient temperature?

Yes

- Go To 2

No

- Replace the sensor
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

2. SHORTED EXHAUST TEMPERATURE SENSOR 1/2 (K186) SIGNAL CIRCUIT TO (K900) RETURN CIRCUIT

Reconnect the Oxygen sensor.

Disconnect the ECM harness connector.


NOTE: Check connectors - Clean/repair as necessary.

Measure resistance of the Temperature sensor 1/2 (K186) signal and (K900) return circuits at the ECM harness connector.


NOTE: The sensor's resistance value increases with decreasing temperature.

Is the resistance 3.2 ± 0.8 ohms at ambient temperature?

Yes

- Go To 5

No

- Go To 3

3. EXHAUST TEMPERATURE SENSOR 1/2 (K186) SIGNAL CIRCUIT OPEN

Disconnect the Exhaust Temperature Sensor 1/2 harness connector.


NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance of the Exhaust Temperature sensor 1/2 (K186) signal circuit between the sensor harness connector and the ECM harness

Is the resistance less than 10 Ohms?

Yes

- Go To 4

No

- Repair the open sensor Signal circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

4. EXHAUST TEMPERATURE SENSOR 1/2 (K900) RETURN CIRCUIT OPEN

Measure the resistance of the Exhaust Temperature Sensor 1/2 (K900) Return circuit between the sensor harness connector and the ECM harness connector.

Is the resistance less than 10 Ohms?

Yes

- Go To 5

No

- Repair the open Return circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

5. EXHAUST TEMPERATURE SENSOR 1/2 (K186) SIGNAL CIRCUIT SHORTED TO ANOTHER CIRCUIT

Measure resistance of the Exhaust Temperature Sensor 1/2 (K186) signal circuit to all other circuits at the ECM harness connector.

Is the resistance more than 100 k ohms?

Yes

- Replace Smart O2 Sensor Module.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Repair the circuits that are shorted together.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test