P038 Code

Showing a P038 code on the dash now along with the silly MAL light (or whatever the orange engine looking light is).

P0038 HO2S Heater Circuit High Voltage Bank 1 Sensor 2

Is this just long form for O2 sensor at Bank 1 Sensor 2? If so, this will be an easy replacement. If not I may have a problem. Although the last O2 sensor code was 138 (P0138 HO2S Circuit High Voltage Bank 1 Sensor 2).

Any suggestions?

MoladoGuy said:

Showing a P038 code on the dash now along with the silly MAL light (or whatever the orange engine looking light is).

P0038 HO2S Heater Circuit High Voltage Bank 1 Sensor 2

Is this just long form for O2 sensor at Bank 1 Sensor 2? If so, this will be an easy replacement. If not I may have a problem. Although the last O2 sensor code was 138 (P0138 HO2S Circuit High Voltage Bank 1 Sensor 2).

Any suggestions?

Click to expand...

Never seen THIS one before. What's a heater circuit?

We have heated O2 sensors on our vehicles. there are 4 wires run to them, 2 wires take readings from the sensor itself, and 2 others are there simply to heat hte O2 sensor up. This is jus to make them start giving accurate readings more quickly so the engine can move out of open loop mode sooner.

But you are correct - it basically implies the O2 sensor is probalby not getting any assistance in heating up. The good news is that after yoru vehicle is on about 5 minutes hte O2s will be heated to proper temp by the exhaust anyways (this is how O2 sensors all worked before heated ones started showing up in the mid 90s). So it's not really critical. I am no expeert on the Jeep ECU - I imagine it's possible the engine could stay running in open loop mode in this condition giving you bad gas mileage.

yes bad mileage is happening to me due to this! 10 mpg ***** ass. wont get fixed until january 8th. stupid o2 sensors

Well, if it's not coming out of open loop mode, and your getting shotty milage, then your engine is also running richer than it should be, which is causing damage to not only your engine, but mainly your exhaust (i.e. cat. converter)

2003KJ said:

Well, if it's not coming out of open loop mode, and your getting shotty milage, then your engine is also running richer than it should be, which is causing damage to not only your engine, but mainly your exhaust (i.e. cat. converter)

Click to expand...

I wouldn't expect the engine to be stuck in open loop if it's the back sensor (his code is for sensor 2). The rear O2s aren't used at all for air/fuel mixture - only to measure efficiency of cats. In my opinion it would be stupid to make the vehicle stick in open loop mode when rear O2s aren't functioning - but I suppose you never know. Unless the #2 sensor is the front...maybe someone can shed light?

Even then, running a bit rich is no problem as far as the engine is concerned (far safer than running too lean!). However 2003KJ is right in that running too rich can destroy your cats. This is all assuming the people who designed the ECU were idiots and decided that rear O2 heaters failing should stick the thing in open loop mode.

indieaz said:

2003KJ said:

Well, if it's not coming out of open loop mode, and your getting shotty milage, then your engine is also running richer than it should be, which is causing damage to not only your engine, but mainly your exhaust (i.e. cat. converter)

Click to expand...

I wouldn't expect the engine to be stuck in open loop if it's the back sensor (his code is for sensor 2). The rear O2s aren't used at all for air/fuel mixture - only to measure efficiency of cats. In my opinion it would be stupid to make the vehicle stick in open loop mode when rear O2s aren't functioning - but I suppose you never know. Unless the #2 sensor is the front...maybe someone can shed light?

Even then, running a bit rich is no problem as far as the engine is concerned (far safer than running too lean!). However 2003KJ is right in that running too rich can destroy your cats. This is all assuming the people who designed the ECU were idiots and decided that rear O2 heaters failing should stick the thing in open loop mode.

Click to expand...

ahh yes, I completely forgot when I was typing earlier that it was bank 1 sensor 2....this then SHOULD be the sensor after the cat., which means good news for you, as that (as mentioned) is really a pointless sensor (other than monitoring the performance of your converter).

Thank goodness for the information! Is Bank 1 the passenger side? I see the above post indicates Bank1 = Passenger and Bank 0 = Driver...Just want to verify.

Thanks all!

Interesting information I found here....

Looked it up in my FSM for the 2003 KJ (should be the same for yours) and heres what I found.


3.7L V-6 Engine:

On this emissions package, 4
sensors are used: 2 upstream (referred to as 1/1 and
2/1) and 2 downstream (referred to as 1/2 and 2/2).
With this emission package, the right upstream sensor
(2/1) is located in the right exhaust downpipe just
before the mini-catalytic convertor. The left upstream
sensor (1/1) is located in the left exhaust downpipe
just before the mini-catalytic convertor. The right
downstream sensor (2/2) is located in the right
exhaust downpipe just after the mini-catalytic convertor,
and before the main catalytic convertor. The
left downstream sensor (1/2) is located in the left
exhaust downpipe just after the mini-catalytic convertor,
and before the main catalytic convertor.


Oxygen Sensor Heater Relay - 3.7L Engine:

On the 3.7L engine, 4 heated oxygen sensors are used. A
separate oxygen sensor relay is used to supply voltage
to the sensors heating elements for only the 1/2
and 2/2 downstream sensors. Voltage for the other 2
sensor heating elements is supplied directly from the
Powertrain Control Module (PCM) through a Pulse
Width Module (PWM) method.

Upstream Sensors - 3.7L Engine:

Two upstream sensors are used (1/1 and 2/1). The 1/1 sensor is the
first sensor to receive exhaust gases from the #1 cylinder.
They provide an input voltage to the PCM. The
input tells the PCM the oxygen content of the
exhaust gas. The PCM uses this information to fine
tune fuel delivery to maintain the correct oxygen content
at the downstream oxygen sensors. The PCM
will change the air/fuel ratio until the upstream sensors
input a voltage that the PCM has determined
will make the downstream sensors output (oxygen
content) correct.

The upstream oxygen sensors also provide an input
to determine mini-catalyst efficiency. Main catalytic
convertor efficiency is not calculated with this package.


Downstream Sensors - 3.7L Engine:

Two downstream sensors are used (1/2 and 2/2). The downstream
sensors are used to determine the correct airfuel
ratio. As the oxygen content changes at the
downstream sensor, the PCM calculates how much
air-fuel ratio change is required.

The PCM then looks at the upstream oxygen sensor voltage, and changes
fuel delivery until the upstream sensor voltage
changes enough to correct the downstream sensor
voltage (oxygen content).
The downstream oxygen sensors also provide an
input to determine mini-catalyst efficiency. Main catalytic
convertor efficiency is not calculated with this
package.

Engines equipped with either a downstream sensor(
s), or a post-catalytic sensor, will monitor catalytic
convertor efficiency. If efficiency is below emission
standards, the Malfunction Indicator Lamp (MIL) will
be illuminated and a Diagnostic Trouble Code (DTC)
will be set. Refer to Monitored Systems in Emission
Control Systems for additional information.


So, you're throwing a code of bank 1 sensor 2. According to the FSM, and if i'm understanding it correctly, that would be the sensor that is listed as (1/2), which is located on the drivers side of the engine block and also are used to determine the air to fuel ratio and are VERY IMPORTANT

Here's an illustration for you if you feel like removing them yourself:

So it WAS some idiot who numbered the O2s after all! ](*,)

I don't understand why they would number them that way. Excellent info! so that would explain why OP is running rich - sounds like he is probably stuck in open loop.

indieaz said:

So it WAS some idiot who numbered the O2s after all! ](*,)

I don't understand why they would number them that way. Excellent info! so that would explain why OP is running rich - sounds like he is probably stuck in open loop.

Click to expand...

Yup.....so it looks like we were both correct from the start.

One of these days i'll finally figure out how the minds of the bozos at DC actually function..... :-k

Whoa!! Sweet post. This is extremely beneficial. I will be replacing this soon. I know it will be a pain to get into but I would rather do it myself. Thanks for the huge write up!

You're welcome Phil.

Please do post a write up of your experiences in replacing this sensor. As far as I know, you are the first on here who's had to replace this particular one....it would be nice to know of any issues to look out for, for those of us who might have to do this down the road.

Same problem

Hi
Does anyone have the same problem?
I own a 05 LTD KJ and 2 days ago check eng ligth went on, when I check it I found the same code P038.

What was the result of the problem?
Did you replace the sensor by yourself? it was difficult

Any help will be appreciated!!!

Thanks in advance

I've not chagned O2s on the liberty yet - but on other cars i've done it on (camaros, mustangs etc.) it was always a super easy 5 minute deal.

I replaced the same one last year on my 04,Very easy to get to and was cheap in price also-I think about $40,Used a scanner to reset mine after replacement-no problems since.

This was much better than my old mazda which the sensors were over $200.