Dodge Ram Truck 1500-2500-3500. Manual — part 822

P0157-O2 SENSOR 2/2 CIRCUIT LOW

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ENGINE - ELECTRICAL DIAGNOSTICS - 3.7L/4.7L/5.7L

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P0157-O2 SENSOR 2/2 CIRCUIT LOW (CONTINUED)

For the Engine circuit diagram (Refer to 9 - ENGINE - SCHEMATICS AND DIAGRAMS).

For a complete wiring diagram Refer to Section 8W.

•

When Monitored:
Engine running for less than 30 seconds and the O2 Sensor Heater Temperature is less than 251°C (484°F)
with battery voltage greater 10.99 volts.

•

Set Condition:
The oxygen sensor signal voltage is below 2.5196 volts for 3 seconds after starting engine. One Trip Fault.
Three good trips to turn off the MIL.

Possible Causes

(K904) O2 RETURN DOWNSTREAM CIRCUIT SHORTED TO GROUND

(K243) O2 2/2 SIGNAL CIRCUIT SHORTED TO GROUND

(K243) O2 SIGNAL CIRCUIT SHORTED TO THE (K904) O2 RETURN DOWNSTREAM CIRCUIT

(K243) O2 SIGNAL CIRCUIT SHORTED TO THE (Z992) O2 2/2 HEATER GROUND CIRCUIT

O2 SENSOR

PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).

Diagnostic Test

1.

O2 SENSOR BELOW 2.52 VOLTS

Start the engine.

Allow the engine to reach normal operating temperature.

With a scan tool, read the 2/2 O2 Sensor voltage.

Is the voltage below 2.52 volts?

Yes

>> Go To 2

No

>> Refer to the INTERMITTENT CONDITION Diagnostic Procedure.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

2.

(K243) O2 2/2 SIGNAL CIRCUIT

Turn the ignition off.

Disconnect the 2/2 O2 Sensor harness connector.

Ignition on, engine not running.

With a scan tool, monitor the 2/2 O2 Sensor voltage.

Is the O2 Sensor voltage above 4.8 volts?

Yes

>> Go To 3

No

>> Go To 5

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ENGINE - ELECTRICAL DIAGNOSTICS - 3.7L/4.7L/5.7L

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P0157-O2 SENSOR 2/2 CIRCUIT LOW (CONTINUED)

3.

O2 SENSOR

Measure the voltage on the (K904) O2 Return Downstream circuit in
the O2 Sensor harness connector.

Is the voltage at 2.5 volts?

Yes

>> Replace the O2 Sensor.

Perform the POWERTRAIN VERIFICATION TEST. (Refer
to 9 - ENGINE - STANDARD PROCEDURE)

No

>> Go To 4

4.

(K904) O2 RETURN DOWNSTREAM CIRCUIT SHORTED TO
GROUND

Turn the ignition off.

Disconnect the C2 PCM harness connector.

Measure the resistance between ground and the (K904) O2 Return
Downstream circuit in the O2 Sensor harness connector.

Is the resistance below 100 ohms?

Yes

>> Repair the short to ground in the (K904) O2 Return Down-

stream circuit.

Perform the POWERTRAIN VERIFICATION TEST. (Refer
to 9 - ENGINE - STANDARD PROCEDURE)

No

>> Go To 8

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ENGINE - ELECTRICAL DIAGNOSTICS - 3.7L/4.7L/5.7L

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P0157-O2 SENSOR 2/2 CIRCUIT LOW (CONTINUED)

5.

(K243) O2 2/2 SIGNAL CIRCUIT SHORTED TO GROUND

Turn the ignition off.

Disconnect the C1 and C2 PCM harness connectors.

Measure the resistance between ground and the (K243) O2 2/2 Signal
circuit in the O2 Sensor harness connector.

Is the resistance below 100 ohms?

Yes

>> Repair the short to ground in the (K243) O2 2/2 Signal cir-

cuit.

Perform the POWERTRAIN VERIFICATION TEST. (Refer
to 9 - ENGINE - STANDARD PROCEDURE)

No

>> Go To 6

6.

(K243) O2 2/2 SIGNAL CIRCUIT SHORTED TO THE (K904) O2 RETURN DOWNSTREAM CIRCUIT

Measure the resistance between the (K243) O2 2/2 Signal circuit and
the (K904) O2 Return Downstream circuit in the O2 Sensor harness
connector.

Is the resistance below 100 ohms?

Yes

>> Repair the short between the (K904) O2 Return Down-

stream circuit and the (K243) O2 2/2 Signal circuit.

Perform the POWERTRAIN VERIFICATION TEST. (Refer
to 9 - ENGINE - STANDARD PROCEDURE)

No

>> Go To 7

DR/DH

ENGINE - ELECTRICAL DIAGNOSTICS - 3.7L/4.7L/5.7L

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