P0137-O2 SENSOR 1/2 CIRCUIT LOW

For a complete wiring diagram Refer to Section 8W.

When Monitored:
With the engine running for less than 30 seconds, the Oxygen Sensor 1/2 heater temperature less than 251° C (484° F), and battery voltage greater than 10.4 volts.
Set Condition:
The PCM detects that the Oxygen Sensor 1/2 signal voltage is below 2.5196 volts for 6 seconds after engine startup. One Trip Fault. Three good trips to turn off the MIL.

Possible Causes

(K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO GROUND

(K904) O2 1/2 RETURN CIRCUIT SHORTED TO GROUND

(K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO THE (K904) O2 1/2 RETURN CIRCUIT

(K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO THE (K299) O2 1/2 HEATER CONTROL CIRCUIT

OXYGEN SENSOR 1/2

POWERTRAIN CONTROL MODULE (PCM)

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - STANDARD PROCEDURE).

Diagnostic Test

1.OXYGEN SENSOR 1/2 VOLTAGE

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

Is the voltage less than 2.52 volts?

Yes

Go to 2

Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

2.(K141) O2 1/2 SIGNAL CIRCUIT VOLTAGE

Is the Oxygen Sensor 1/2 voltage above 4.8 volts?

Yes

Go to 3

Go to 5

3.OXYGEN SENSOR 1/2

Is the voltage at 2.5 volts?

Yes

Replace the Oxygen Sensor 1/2.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

Go to 4

4.(K904) O2 1/2 RETURN CIRCUIT SHORTED TO GROUND

Is the resistance below 100 ohms?

Yes

Repair the (K904) O2 1/2 Return circuit for a short to ground.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

Go to 8

5.(K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO GROUND

Is the resistance below 100 ohms?

Yes

Repair the (K141) O2 1/2 Signal circuit for a short to ground.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

Go to 6

6.(K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO THE (K904) O2 1/2 RETURN CIRCUIT

Is the resistance below 100 ohms?

Yes

Repair the short between the (K904) O2 1/2 Return circuit and the (K141) O2 1/2 Signal circuit.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

Go to 7

7.(K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO THE (K299) O2 1/2 HEATER CONTROL CIRCUIT

Is the resistance below 100 ohms?

Yes

Repair the short between the (K299) O2 1/2 Heater Control circuit and the (K141) O2 1/2 Signal circuit.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

Go to 8

8.POWERTRAIN CONTROL MODULE (PCM)

Were any problems found?

Yes

Repair as necessary.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).