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eauto
eauto, The Car Guy
Category: Jeep
Satisfied Customers: 15390
Experience:  ase mechanic 16 Plus years in the field
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I had a p0051 02sensor code... Changed the sensor and light

Customer Question

I had a p0051 02sensor code... Changed the sensor and light popped up again... Put in on the scanner and noticed that every time the truck hit ol-drive, it would set off the check engine light...... Any reasons why????
Submitted: 1 year ago.
Category: Jeep
Expert:  eauto replied 1 year ago.

what code are you getting now? still the p0051?

Customer: replied 1 year ago.
Customer: replied 1 year ago.
Any thoughts????
Expert:  eauto replied 1 year ago.

did you change up stream or down stream? which bank? and a direct fit sensor? or universal?

Customer: replied 1 year ago.
Bank 2 sensor 1 ( upstream )
Expert:  eauto replied 1 year ago.

so the passenger side correct?

Expert:  eauto replied 1 year ago.

P0051 02 SENSOR HEATER CIRCUIT LOW2/1: Possible Harness damage.;Check Fuse #16 in PDC, if it's blown and perform power train test for the code looking for a short to ground. A production change was preformed on vehicles built after 6/2/03 to take care of erroneous codes, a software fix is needed to correct vehicles built before 6/2/03 this will be in the form of a software flash

Check for excessive heat from exhaust melting the harness by the 02 sensor

Ignition on, engine not running.

With the scan tool, read DTCs

NOTE: If P0136 is set with the P0031 or P0051, inspect the related fused and

repair as necessary.

With the scan tool, actuate the O2 Heater test.

Monitor the O2 Heater Voltage for 5 minutes.

Did the voltage drop down close to zero during the Heater test?

Yes The conditions to set this code are not currently present

No Go To 2NOTE: Stop the actuation before continuing.

2

Turn the ignition off.

Disconnect the O2 Sensor harness connector.

Measure the resistance of the O2 Heater Element at the O2 Sensor connector

(component side).

The resistance value for a 4.0L O2 Heater element is 4.0 to 5.0 ohms at 70°F

NOTE: The resistance value will increase with warmer temperatures.

Is the resistance within the listed specifications?

Yes Go To 3

No Replace the O2 Sensor.

3

Ignition on, engine not running, and the Sensor harness connector still disconnected.

With the scan tool, actuate the O2 Heater Test.

Using a 12-volt test light connected to ground, check for voltage on the Fused

ASD Relay Output in the O2 Sensor harness connector.

Does the test light illuminate brightly?

Yes Go To 4

No Repair the open or short to ground in the Fused ASD

Relay/O2 Heater Supply circuit. Inspect the related fuse and repair as necessary.

NOTE: Stop the actuation before continuing.

4

Turn the ignition off.

Disconnect the PCM harness connectors.

Measure the resistance of the O2 Heater Control circuit (PWM) from the O2 Sensor

harness connector to the PCM harness connector.

Is the resistance below 5.0 ohms?

Yes Go To 5

No Repair the excessive resistance in the PWM Heater Control circuit.

5

Measure the resistance between ground and the O2 Heater Control (PWM) circuit at

the O2 Sensor harness connector.

Is the resistance below 100 ohms?

Yes Repair the short to ground in the Heater Control (PWM) circuit.

No Go To 6

6

NOTE: Before continuing, check the PCM harness connector terminals for

corrosion, damage, or terminal push out. Repair as necessary.

inspect the wire harness and connectors. Pay

particular attention to all Power and Ground circuits.

If there are no possible causes remaining

Replace and program the Power train Control Module

since it is an early build a software update may fix your concern without doing all of this, the normal charge for a software update is 1 hour

P0051-O2 SENSOR 2/1 HEATER CIRCUIT LOW

When Monitored: Battery voltage above 10.6 volts, ASD is powered up, and O2 heater is

on.

Set Condition: Desired state does not equal Actual state.

POSSIBLE CAUSES

O2 HEATER TEST

O2 SENSOR HEATER ELEMENT

(F142) FUSED ASD RELAY OUTPUT CIRCUIT OPEN

HEATER CONTROL CIRCUIT OPEN

HEATER CONTROL CIRCUIT SHORTED TO GROUND

PCM

Customer: replied 1 year ago.
If I leave it idling, no code is set off...
Customer: replied 1 year ago.
It will idle forever with no code being set...It's more when you accelerate aggressively that it comes on ( check engine light )
Customer: replied 1 year ago.
I can't activate the o2 sensors with the scan tool I have...
Expert:  eauto replied 1 year ago.

can you watch the heater circuit?